SPECIFICATION 200-023

275/110/22kV kV Power Transformers

March 2016

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Specification 200-23 275/110/22kV Power Transformers Table of Contents

1.General ........................................................................................................................ 5 1.1 Scope ......................................................................................................... 5 1.2. Standards .................................................................................................. 6

1.2.1 European Standards ............................................................. 6 1.2.2 International Standards ......................................................... 8 1.2.3 British standards ................................................................... 8 1.2.4 ENA Standards ..................................................................... 8 1.2.5 NIE Networks Specifications ................................................. 9

1.3. System Conditions ................................................................................... 10 1.3.1 Network parameters ............................................................ 10 1.3.2 Network short circuit levels and duration ............................. 10

1.4 Service conditions .................................................................................... 10 1.5 Auxiliary supplies ..................................................................................... 10

Section 2. Electrical characteristics .......................................................................... 11 2.1. Type of transformer ................................................................................. 11 2.2. Rated voltages ......................................................................................... 11 2.3. Rated power ............................................................................................ 11 2.4. Overload capability .................................................................................. 12 2.5. Voltage ratios ........................................................................................... 13 2.6. Winding connections and vector group .................................................... 13 2.7. Flux density and harmonics ..................................................................... 14 2.8. Insulation levels ....................................................................................... 14 2.9. Impedance voltage .................................................................................. 14 2.10. Short circuit performance ......................................................................... 14 2.11. Over-fluxing ............................................................................................. 15 2.12. Partial discharge ...................................................................................... 15 2.13. Losses ..................................................................................................... 15 2.14 Parallel Operation .................................................................................... 16

Section 3. Design and construction .......................................................................... 16 3.1 Quality assurance .................................................................................... 16 3.2 On-load tap-changer ................................................................................ 16

3.2.1 General ............................................................................... 16 3.2.2 Performance ....................................................................... 16 3.2.3 Tap-changer compartment .................................................. 17 3.2.4 Drive mechanism ................................................................ 17 3.2.5 Pressure relief device .......................................................... 18

3.3 Tap-changer control and indication .......................................................... 18 3.3.1 General ............................................................................... 18

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3.3.2 Local control and indication ................................................. 18 3.3.3 Tap-changer mechanism box .............................................. 19

3.4 Cooling and temperature control .............................................................. 19 3.4.1 Radiators ............................................................................. 19 3.4.2 Fans and/or pumps ............................................................. 20 3.4.3 Temperature control ............................................................ 20 3.4.4 Winding temperature indicators (WTI's) .............................. 21 3.4.5 Oil temperature indicator (OTI) ........................................... 22 3.4.6 Fibre Optic Connected Temperature Measurement ............ 22

3.5 Control cubicle ......................................................................................... 23 3.5.1 General ............................................................................... 23 3.5.2 Control cubicle internal temperature ................................... 24 3.5.3 Cubicle equipment .............................................................. 24

3.6 Tank and accessories .............................................................................. 24 3.6.1 General ............................................................................... 24 3.6.2 Tank vacuum and pressure ................................................. 25 3.6.3 Conservator tank ................................................................. 25 3.6.4 Breathers ............................................................................ 25 3.6.5 Pressure relief device .......................................................... 26 3.6.6 Low oil level device ............................................................. 26 3.6.7 Oil sampling points .............................................................. 26 3.6.8 Oil filtration and vacuum processing ................................... 26 3.6.9 Lifting lugs ........................................................................... 27 3.6.10 Jacking pads ....................................................................... 27 3.6.11 Hauling eyes ....................................................................... 27 3.6.12 Earthing terminals ............................................................... 27 3.6.13 Oil valves ............................................................................ 27 3.6.14 HV neutral CT accommodation ........................................... 28 3.6.15 On-line transformer condition based diagnostics ................ 28 3.6.16 Ancillary and control cable installation ................................ 28 3.6.17 Removable access covers (Inspection hatches) ................. 28

3.7 Transformer oil ......................................................................................... 29 3.7.1 General ............................................................................... 29 3.7.2 PCB ..................................................................................... 29

3.8 Gas relays and sampling device .............................................................. 29 3.8.1 Gas operated relays ............................................................ 29 3.8.2 Gas sampling device ........................................................... 29

3.9 Bushings, link boxes and terminals .......................................................... 30 3.9.1 General ............................................................................... 30 3.9.2. Bushings ............................................................................. 30 3.9.4 Clearances .......................................................................... 32 3.9.5 Current Transformers .......................................................... 32 3.9.6 Neutral and Tertiary Terminal Location ............................... 33 3.9.7 Terminals ............................................................................ 33 3.9.8 Terminal markings............................................................... 33

3.10 Noise and vibration .................................................................................. 34 3.11 Labels and rating plates ........................................................................... 35

3.11.1 General ............................................................................... 35

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3.11.2 Rating plate ......................................................................... 35 3.11.3 Locations of valves and air release cocks ........................... 35 3.11.4 Gas points ........................................................................... 35 3.11.5 Direction of rotation ............................................................. 35 3.11.6 Control and auxiliary equipment .......................................... 35 3.11.7 400V connections ............................................................... 36 3.12 Safety features .................................................................... 36

Section 4. Cleaning and painting .............................................................................. 37 4.1 General .................................................................................................... 37 4.2 Surface preparation ................................................................................. 37

4.2.4 The internal oil surfaces of coolers and radiators shall be flushed with oil. The ........................................................ 37

4.2.5 Special attention shall be given to items, which are to be hot-dip galvanised to ............................................................ 37

4.3 Surface Protection ................................................................................... 38 4.4 Coating systems ...................................................................................... 38

4.4.1 Painting ............................................................................... 38 4.5 Inspection ................................................................................................ 39 4.6 Other requirements .................................................................................. 39

Section 5. Tests ........................................................................................................ 40 5.1 General .................................................................................................... 40 5.2 Type tests ................................................................................................ 40 5.3 Routine tests ............................................................................................ 41 5.4 Special tests ............................................................................................ 42 5.5 Site tests .................................................................................................. 42 5.6 Test certificates ........................................................................................ 43 5.7. Witnessing of tests ................................................................................... 43

Section 6. Packing, installation, manufacture and training ........................................ 44 6.1 Packing and prohibited materials ............................................................. 44 6.2 Installation and assembly ......................................................................... 44 6.3 Manufacturing programme and progress reports ..................................... 45 6.4 Spare parts .............................................................................................. 45 6.5 Training .................................................................................................... 45 6.6 Drawings and information ........................................................................ 45

7.Quality Assurance And Checks .................................................................................. 47

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Schedules Schedule A General particulars of definite work Schedule B Commencement dates etc. Schedule C Access facilities to site Schedule D Guaranteed rated vales and characteristics Section A 240 MVA transformer Schedule E Prices and delivery Section A 240 MVA transformer Schedule F Price schedule of recommended spare parts Schedule G Schedule of deviations from specification This Specification comprises 68 pages.

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1. General 1.1. Scope This specification states the requirements for oil immersed 275/110/22kV power transformers. The transformers offered by tenderers shall be designed for a minimum of 40 years service. The Supplier shall have complete responsibility for the design, manufacture, works testing, off loading and assembly on site of the transformer and all ancillary equipment. Site works shall include commission testing of the transformer and preparation for service including all oil handling and filtering at sites within Northern Ireland as specified by NIE Networks. NIE Networks shall be responsible for the transformer plinth foundations, auxiliary supplies, cabling from the control and/or mechanism cubicles to the substation control room and tap change control cubicle. Following award of contract the tenderer shall make available design details, methods and drawings for the purpose of design review prior to the completion of final design and construction. The design details and drawings shall include core and winding construction and materials, oil flow methodology, thermal calculations, stray fluxing mitigation methods and winding construction methodology used to withstand NIE Networks assigned network short circuit levels. In addition, Recurrent Surge Oscillogram and Finite Element Modeling plots, tap changer and bushing details shall be provided. The tenderer shall also provide details of all calculation methods including correction factors to be used during type and routine testing. Details of all instruments to be used during measurement and/or testing and their method of calibration certification shall be made available. An inventory of all materials to be used in the construction of the transformer/s and their supplier/s shall be made available to NIE Networks prior to commencement of construction. Any proposed deviation from the named materials and their supplier/s during the term of this contract shall only be made following consultation with NIE Networks. During the term of this contract the manufacturer shall inform NIE Networks of any material defects, which arise during batch testing of materials. In addition, details of failures of materials used in the construction of the transformer/s supplied by external manufacturers, which the transformer manufacturer is made aware of, shall be made available to NIE Networks. The document has been edited to ensure that it meets the requirements of Clauses 11 of the Utilities Supply and Works Contracts Regulations 1992 (SI1992 No. 3279).

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1.2. Standards The transformers shall in general comply with the references and related documents below. However where any provision of this NIE Networks specification differs from those listed, the provision of this specification shall apply.

1.2.1 European Standards BS EN 50180 Bushings above 1kV up to 36kV and from 250A to 3.15kA for liquid

filled transformers. BS EN 50181 Plug-in type bushings above 1kV up to 52kV and from 250A up to

2.5kA for equipment other than liquid filled transformers. BS EN 50299 Oil-immersed cable connection assemblies for transformers and

reactors having highest system voltage for equipment Um from 72.5 to 550kV.

BS EN 60044-1: Instrument transformers. Current transformers. BS EN 60076-1 (2011): Power Transformers. General. BS EN 60076-2 (2011): Power Transformers. Temperature rise for liquid-immersed

transformers. BS EN 60076-3 (2013): Power Transformers. Insulation Levels, dielectric tests and external

clearances in air. BS EN 60076-4 (2002): Power Transformers. Guide to the lightning impulse and switching

impulse testing. Power transformers and reactors. BS EN 60076-5 (2006): Power Transformers. Ability to withstand short circuits. BS EN 60076-10 (2001): Power Transformers. Determination of sound levels. BS EN 60137 (2008): Insulated bushings for alternating voltages above 1000V. BS EN 60214-1 (2014): Tap changers. Performance requirements and test methods. BS EN 60269-1 Low voltage fuses. General Requirements. BS EN 60296 (2012): Fluids for electrotechnical applications. Unused mineral insulating

oils for transformers and switchgear. BS EN 60507 (2014) Artificial pollution test on high-voltage ceramic and glass

insulators to be used on a.c. systems

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BS EN 60529 Classification of degrees of protection provided by enclosures BS EN 60567 (2011): Oil filled electrical equipment. Sampling of gases and analysis of free

and dissolved gases. Guidance. BS EN 60599 (2016): Mineral oil impregnated electrical equipment in service. Guide to the

interpretation of the analysis of gases in transformers and other oil-filled electrical equipment in service.

BS EN 60641 (2008) Specification for pressboard and presspaper for electrical purposes.

Definitions and general requirements BS EN 60688 (2013) Electrical measuring transducers for converting A.C. and D.C.

electrical quantities to analogue or digital signals BS EN 60947 (2009): Low-voltage switchgear and control gear. BS EN 61619: Insulation liquids. Contamination by polychlorinated biphenyls

(PCBs). Method of determination by capillary column gas chromatography.

BS EN 61936-1: Power installations exceeding 1kV A.C. Common clauses.

BS EN 61672: Electroacoustics. Sound level meters. BS EN 61869-1 Instrument transformers. General requirements. BS EN 61869-2 (2012) Instrument transformers. Additional requirements for current

transformers. BS EN 61869-3 (2011) Instrument transformers. Additional requirements for inductive voltage

transformers. BS EN ISO 1461 (2009): Hot dip galvanized coatings on fabricated iron and steel articles.

Specifications and test methods. BS EN ISO 8501-1 (2007): Preparation of steel substrates before application of paints and

related products. BS EN ISO 9001 (2008): Quality management systems. Requirements. BS EN ISO 14001 Environmental management systems. Requirements with guidance

for use. BS EN ISO 17834 (2003) Thermal spraying. Coatings for protection against corrosion and

oxidation at elevated temperatures.

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1.2.2 International Standards IEC 60076-7 Power Transformers. Loading guide for oil-immersed power

transformers. IEC 60214-2 Tap changers Part 2: Application Guide

IEC 60815: Guide for the selection of insulators in respect of polluted conditions. IEC 60997: Determination of polychlorinated biphenyls (PCBs) in mineral

insulating oils by packed column gas chromatography. IEC 60840: Power cables with extruded insulation and their accessories for rated

voltages above 30kV up to 150kV – Test methods and requirements.

1.2.3 British standards BS 148 (2009) Insulating oil for transformers and switchgear BS 381C (1996) Specification for colours for identification, coding and special

purposes. BS 5825 (1980) Specification for low voltage switchgear and controlgear for industrial

use – mounting rails. G-profile for the fixing of terminal blocks.

BS 5493: Code of practice for protective coatings of iron and steel structures against corrosion.

BS 7870-4.10 (2011) LV and MV polymeric insulated cables for use by distribution and

generation utilities. Specification for distribution cables with extruded insulation – of rated voltages of 11kV to 33kV. Single-core 11kV to 33kV cables.

BS7912: Power cables with XLPE insulation and metal sheath, and their

accessories, for rated voltages from 66kV to 132kV – Requirements and test methods

1.2.4 ENA Standards ENA TS 98-1 (1997): Surface preparation and coating systems for new plant and

equipment. ENA TS 50-18 (2013) Application of Ancillary Electrical Equipment.

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1.2.5 NIE Networks Specifications 211-03 Ancillary Electrical Equipment

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1.3. System Conditions

1.3.1 Network parameters 275kV: Nominal voltage: 275kV Highest system voltage: 300kV 3 phase, 50Hz, with neutral point solidly earthed 110kV: Nominal voltage: 110kV Highest system voltage: 121kV

3 phase, 50Hz, with neutral point solidly earthed

1.3.2 Network short circuit levels and duration 3 phase single phase duration 275kV network 40kA 40kA 3 secs 110kV network 40kA 40kA 3 secs 1.4. Service conditions The transformers will be located outdoors in an electrically exposed location less than 1,000 metres above sea level, in a salty atmosphere with high humidity. The following ambient temperature conditions shall apply: Environmental conditions Value Minimum temperature -25°C Annual average temperature +20°C Maximum temperature +40°C Maximum daily average temperature

+30°C

Table 1 Environmental Conditions 1.5. Auxiliary supplies Auxiliary supplies shall be available as follows: 400/230V 3 phase a.c. 50 Hz for fans, pumps, heaters etc. 110V DC for control.

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Incoming LV supply terminals shall be suitable sized to facilitate connection of a supply cable having 35mm2 stranded Cu conductors. D.C supply either 24V DC, 48V DC or 110V DC for control and indication, as in Table 2 specified below. Nominal DC Voltage 110V 48V 30V *Rated DC System Voltage 125V 54V System Limits – Max. 137.5V 60V 27V System Limits – Min. 102V 43V Table 2 Nominal DC Voltages *Connected DC equipment shall be capable of operating continuously at the ‘Rated DC System Voltage’ without any adverse effect or impact upon the normal life of the device.

Section 2. Electrical characteristics 2.1. Type of transformer The transformer shall be three phase 50Hz, oil immersed, with on-load tap-changer, and of the common and series winding auto design. A tertiary winding shall also be provided. The cooling radiators shall normally be mounted on to the main tank of the transformer - an integral type design. Unless NIE Networks request a separate cooler bank arrangement. The transformer cooling shall be ONAN/ONAF/OFAF. Transformer designs utilizing non-linear voltage limiting devices are not acceptable. The design shall be sufficiently rigid to resist distortion when the transformer is lifted and transported. The tenderer shall demonstrate that the materials used in the construction of the transformer are capable of 40 year service life. 2.2. Rated voltages The rated nominal voltages of the windings shall be:

• HV 275kV • LV 110kV • Tertiary 22kV

2.3. Rated power 2.3.1 The rated power of the transformer shall be selected from Table 3 below and shall

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be stated in Schedule A:

BS EN 60076 Rated power Main Winding ONAN/ONAF/OFAF 120/240MVA Tertiary ONAN 60 MVA

Table 3 Rated Power

2.3.2 The transformer shall be capable of supplying its rated power continuously for all tap positions and at any voltage ratio within the limits detailed in Table 4 and with rated voltage on the low voltage winding. Maximum ratio 110kV -5% 275kV +12% Minimum ratio 110kV +5% 275kV -8.8%

Table 4 Voltage Ratios 2.3.3 The transformer shall be capable of supplying at least 50% of its rated power during natural cooling (ONAN). Additional cooling for the rated power may be forced air (ONAF) or forced air with forced oil (OFAF). The rated power of the tertiary (60MVA) shall apply to ONAN, ONAF and OFAF operation of the main winding. Its shall be possible to load the tertiary to its assigned rating without affecting the 120/240MVA rating of the transformer.

2.3.4 The transformer shall be capable of supplying its rated power continuously under the stated ambient temperature conditions, without the temperature rise of the top oil exceeding 60K, and without the temperature rise of the windings, as measured by resistance, exceeding 65K. 2.3.5 The tertiary winding shall be capable of carrying a continuous load as specified in Table 3. 2.3.6 The temperature rise on any part of the tank up to 2.6m above the level of the plinth, when operating at rated power, shall not exceed 60C. Above 2.6m, it shall not exceed 80C. 2.4. Overload capability 2.4.1 The transformer, its internal connections, leads, bushings and tap changer/s and all other associated equipment shall be designed so that over-loading in accordance with IEC 60076-7 is possible. 2.4.2 The transformer shall be capable of the following normal cyclic loading without exceeding a hot spot temperature of 120 C at 10 C ambient.

2.4.3 The tenderer shall submit option costs for a ‘special test’ to establish the actual

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temperature rise and hot spot temperatures during overload operation, as shown in Table 5 below.

Overload Time 0.7 p.u. 16 hours 1.2 p.u. 8 hours 0.7 p.u. 16 hours

Table 5 Overload Capability

2.4.4 The complete transformer shall be capable of extreme emergency short time loadings up to 1.5 p.u. (for 30 mins) in accordance with IEC 60076-7. 2.4.5 The calculation of the cyclic loading capability shall be according to the method given in IEC 60076-7 based on the actual temperature rise test results. 2.4.6 Bushings, leads and tap changers shall be suitably rated and capable of operating at 150% of the transformer rated power, see Clause 2.4.4 above. The tenderer shall provide evidence of the assigned overload rating. 2.5. Voltage ratios The on-load tap-changer fitted to transformers shall be arranged to give variations of transformation ratio in 18 equal steps for a total range of +15% to -15% of 110kV when the high voltage terminals are maintained at a constant voltage of 275kV. The category of voltage variation shall be 'Constant Flux Voltage Variation' (C.F.V.V.). The tap position variations shall be as shown in Table 6 below. No. of Positions Variation per step 19 18 of 1.67%

Table 6 Tap Position Variation The tappings can be used to increase the 275kV terminal voltage to a maximum of 300kV at full load. 2.6. Winding connections and vector group The auto-transformer shall be of the common and series design connected as shown in Table 7 below. Connection of Windings Vector Group H.V. – L.V. Yy0 (auto-connected star) H.V. – Tertiary Yd1 Table 7 Connections & Vector Groups

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A break in the corner of the tertiary (delta) winding is required for the purposes of testing. Suitable removable links shall be provided to enable the opening of the tertiary winding.

2.7. Flux density and harmonics 2.7.1 The flux density at any point of the magnetic circuit when at rated voltage and frequency shall not exceed the following:

• Nominal ratio at no load kV (275/110) - 1.55 Tesla • Maximum ratio at no load kV (324/110) - 1.825 Tesla

Transformers shall be capable of continuous operation at 110% of rated voltage. 2.8. Insulation levels The complete transformer arranged for service shall be designed and tested to the following insulation levels in accordance with BS EN 60076-3, shown in Table 8 below.

Line Terminals (kV) HV Neutral HV LV Tertiary

Nominal Voltage 275 110 22 - Highest Voltage for Equipment 300 123 24 - Min Induced Overvoltage (power frequency) withstand (kV rms)

Clause 11.3 BS

EN 60076-3

230 50

Min Lightning Impulse Voltage withstand (kVp) 1050 550 125 Min Switching Impulse Voltage withstand (kVp)

850

Min Separate Source Power Frequency Voltage withstand (kV rms)

As HV neutral

230 50 Min 38kV

Table 8 Insulation Levels

The 1-minute power frequency withstand voltage for the auxiliary and control circuits shall be 2kV rms. 2.9. Impedance voltage The design impedance voltage, with tolerances in accordance with BS EN 60076, of the transformer shall be as stated in Schedule A at nominal tap. 2.10. Short circuit performance

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The transformer shall be capable of withstanding for 3 seconds a metallic short circuit on the terminals of either the HV or LV winding with rated voltage on the other winding and the tap-changer in any position. The manufacturer shall demonstrate, during design review, the capability of the proposed transformer design to withstand the network short circuit levels and duration detailed in Clause 1.3.2. 2.11. Over-fluxing The transformer shall be designed and guaranteed to meet the following overfluxing requirements without damage on any tap while carrying the rated current for that tap without exceeding the temperature rise specified in Clause 2.3.4. Continuous: 115% of rated volts/Hz 1 minute: 125% of rated volts/Hz 10 seconds: 140% of rated volts/Hz The above shall be confirmed during transformer testing. 2.12. Partial discharge The transformer shall be partial discharge free at 120% of rated line voltage as the voltage is reduced from 150% of rated voltage, i.e. there shall be no significant rise above background level at 120% rated voltage. 2.13. Losses 2.13.1 The design of the transformer/s shall generally be such that the Minimum Peak Efficiency is in accordance with the requirements of Commission Regulation (EU) No 548/2014 Table 1.7. The manufacturer shall provide evidence of the Peak Efficiency calculation. However NIE Networks require that the transformer shall comply with the following maximum losses inclusive of any allowable tolerance, detailed in Table 9.

Rating (MVA) No load loss (kW)

Load loss at 75°C (kW)

Cooler Motor Losses (kW)

Total Losses (kW)

240MVA 40kW 550kW 10kW 600kW Table 9 Losses 2.13.2 The maximum values for losses at nominal tap measured during routine and type testing shall be as detailed in Schedule D.

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2.14 Parallel Operation The auto-transformers are to be used in parallel operation with existing auto-transformers. Details of such transformers will be supplied with the tender documents.

Section 3. Design and construction

3.1 Quality assurance The Tenderer shall be accredited to BS EN ISO 9001, or submit satisfactory evidence to demonstrate their quality system and inspection procedures are such as to ensure compliance with this standard. 3.2 On-load tap-changer

3.2.1 General The transformer shall be provided with an on-load tap-changer mounted in the high-voltage winding. The tap changers shall be contained within a separate compartment to the main tank having barrier boards to facilitate connection of the tap changer with the main winding. In addition, the tap changer diverter switches shall be mounted in a self contained chamber to ensure that its mineral insulating oil is kept separate from the tap changer selector and the main winding. The tap-changer shall be in accordance with BS EN 60214-1 and IEC 60214-2.

3.2.2 Performance The tapping range, the number of steps and tap positions shall be in accordance with Clause 2.5 - Voltage ratios. The tap-changer shall be capable of withstanding the voltages set out in Clause 2.8 - Insulation levels. The tap-changer shall be capable of operating continuously at full rated power in forward and reverse power flow operation at all tap positions. It shall also be designed so that overloading of the transformer in accordance with Clause 2.4 is not restricted.

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3.2.3 Tap-changer compartment The tap changer shall be positioned behind a full height barrier to facilitate inspection and maintenance of the tap-changer diverter and selector switch, whilst maintaining the level of oil over the core and windings. Adequate access and space within the chamber for personnel shall be provided for such inspection and maintenance, which shall include the provision of an adequate number of inspection and maintenance hatches to be agreed at the design review stage. Special tools and any lifting devices required to enable removal of the tap-changer for inspection and/or maintenance shall be provided.

3.2.4 Drive mechanism The tap-changer shall be driven by a motor-operated mechanism incorporating a stored-energy device, which shall ensure that once a change of tap begins it is completed and so shall ensure that the mechanism does not fail in an intermediate position on loss of the supply voltage to the motor. The motor drive control shall be such that on initiation of a tap-change operation by means of a control switch or push-button, the tap-changer shall complete its movement from one service position to an adjacent one irrespective of whether or not the control switch or push-button has been operated continuously during the running time of the motor drive. Another operation shall only be possible when the control switch or push-button has been released and the control system is again in the rest position. The motor shall be rated for 400/230V 50Hz, and shall operate satisfactorily at any voltage between 85% and 115% of rated voltage. Limit switches shall be provided to prevent over-running of the tap-change mechanism. These shall be directly connected in the motor circuit. In addition mechanical end stops shall be fitted to prevent over-running of the mechanism under any conditions. If the tap-changer is housed in-tank, then any external drive shaft shall be enclosed in protective conduit. The control cubicle shall be positioned remote from the tap changer, if externally mounted; to ensure that any local electrical operations are not carried out in close proximity to the tap changer tank should a failure occur. This requirement also includes the proximity to any output piping connected to pressure relief devices.

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3.2.5 Pressure relief device Each tap changer compartment shall be fitted with a suitable pressure relief device with normally open 2 x trip and 1 x alarm contacts, which are set to open on excess pressure and to reseal automatically. They shall be located to ensure that discharge from the PRD is directed towards the ground so as not to cause danger to personnel. 3.3 Tap-changer control and indication

3.3.1 General Each transformer shall be supplied with a tap-changer mechanism box containing all control equipment associated with the on-load tap-changer. Internal wiring shall comply with the NIE Networks specification 211-03.

3.3.2 Local control and indication The tap-changer mechanism box installed at the transformer shall contain all the electrical and mechanical parts associated with the tap-changer. The following facilities shall be provided in the mechanism box: (1) Facilities for manual mechanical operation of the tap changer. (2) An interlock which will interrupt the electrical supply to the drive motor when the manual operation device is engaged. (3) A selector switch for "Local/Off/Remote" control of the tap-change facility. A mechanical tap position indicator shall be provided. This shall be visible to a person standing at ground level through a window on the front of the mechanism box. Tap position transmitters shall be provided to: (1) Signal tap position to the control room. (2) Signal tap position to a System Control Centre, via the NIE Networks SCADA system. A tap changer monitoring device of the supplier’s recommendation shall be offered.

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3.3.3 Tap-changer mechanism box The mechanism box shall have a hinged door suitable for locking with a padlock, having an 8mm diameter shank, and shall be mounted on the transformer tank using anti-vibration mountings. The degree of protection of the mechanism box shall be IP54 of BS EN 60529. The mechanism box shall be fitted with an anti-condensation space heater, which shall be controlled as follows: (1) A humidistat with an adjustable operating range. (2) A cut-out thermostat with an adjustable operating range, to prevent overheating. These circuits shall operate at 230V, 50Hz. An internal lamp controlled by a door switch shall be provided. Approximately 10% spare terminals shall be provided in each mechanism box. A drawing, on robust material to the Purchaser's approval, indicating the connections within the box, shall be fixed to the inside of the door. 3.4 Cooling and temperature control

3.4.1 Radiators The cooling radiators shall be tank mounted and shall be detachable from the tank for transport and maintenance. Lockable shut-off valves and appropriate blanking plates shall be provided on the tanks of the transformers for this purpose. The cooler banks shall be arranged so that they may be fed from the either end of the transformer. This will include each pipe connection fitted with appropriate expansion joints, including anti-vibration inserts. An alternative free standing cooler design may be required to facilitate the installation of a noise enclosure. The tenderer shall submit alternative design options at the time of tender. An air-vent and draining plug shall be provided on each radiator for the purpose of air removal following oil filling of the transformer.

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3.4.2 Fans and/or pumps The forced air/oil cooling shall be provided by electric motor driven fans/pumps, mounted at low level. Each motor shall be rated for 400/230V 50Hz and shall operate satisfactorily at any voltage between 85% and 115% of rated voltage. Motor enclosures shall be Class IP44 of BS EN 60529. Fan enclosures shall be Class IP20 of BS EN 60529. Motors shall be suitably constructed and mounted so as to prevent the pooling of water, which could lead to corrosion and/or cause mal-operation of the motor e.g bearing failure. The fan enclosure shall be made of suitable stainless steel to prevent corrosion. Details shall be submitted at time of tender for review. Fans shall be mounted at the bottom of the radiators so as to facilitate replacement and/or repairs of the fan/s at ground level. Motor operation shall be controlled by the thermostats as detailed in Clause 3.4.3. Each motor shall be fitted with volt free contacts to provide indication should the motor fail to operate. Fans shall be fixed to the transformer/radiator with anti-vibration mountings. If oil pumps are provided, appropriate measures shall be taken to prevent the initial oil surge on starting from operating the gas relay. Manual control shall be provided in the control cubicle for the cooling system (fans and pumps). Electrical isolation for maintenance of fans and pumps shall be provided by lockable MCBs. Oil surge relays where supplied, must not operate when cooling pumps start or stop under automatic or manual control or in the momentary loss of auxiliary supply. Appropriate electrical protection devices are required for the fan and pump motors. Fan and motor control circuits shall be fitted with an automatic control function to facilitate running (exercising) for a period of 30 minutes once every 7 day period. Fans and/or pumps shall comply with the requirements of Section 1.4. Control and power supply cables shall be contained within an open stainless steel tray and shall be held in place using plastic backed (covered) stainless steel straps.

3.4.3 Temperature control The fans and pumps shall be automatically switched on when the winding temperature exceeds

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preset values and shall be switched off when the temperature falls below these values.

3.4.4 Winding temperature indicators (WTI's) Winding temperature indicators, temperature probes and associated current transformers shall be required for HV, LV and tertiary windings. Winding temperature indicators shall be accommodated in a control cubicle mounted on the transformer tank. Each transformer shall be provided with uniformly divided winding temperature indicators, temperature probes and associated current transformers. The design of the WTI's shall be such that the equipment will not sustain damage or mal-operate due to vibration in service. Anti-vibration mountings shall preferably be integral with the indicator case. The winding temperature indicators shall be of an electro-mechanical design and be labelled in English. A transducer shall be fitted to each WTI that will give a 4 to 20mA milliamp output for the temperature range of the WTI. This shall be wired into the transformer control cubicle. Winding temperature indicator heater coil current transformers, shall be mounted in the HV L2, LV l2 and tertiary l12 phase. Current transformers shall be in accordance with BS EN 60044-1. Accuracy class for these heater coil CTs shall be class 1.0 Each winding shall be provided with a WTI as detailed in Table 10 below.

WTI Label No of Elements/WTI Electrical Contacts per WTI

HV Winding 3 Control, Alarm, Trip

LV Winding 3 Control, Alarm, Trip

Tertiary Winding 3 Control, Alarm, Trip Table 10 WTI requirements The values of WTI shall not vary by more than plus or minus 30C from the values derived during temperature rise tests. The adjustable contacts listed shall have the following characteristics: Control: Adjustable setting 500C to 1000C Adjustable differential 150C to 300C Alarm: Adjustable setting 800C to 1500C Fixed differential not more than 100C Trip: Adjustable setting 800C to 1500C Fixed differential not more than 100C

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WTI's shall be calibrated at time of transformer heat run testing in accordance with manufacturers instructions. The supplier shall use a type of temperature probe that shall be subject to NIE approval.

3.4.5 Oil temperature indicator (OTI) Two oil temperature indicators shall be accommodated in a control cubicle mounted on the transformer tank. The design of the OTI shall be such that the equipment will not sustain damage or mal-operate due to vibration in service. Anti-vibration mountings shall preferably be integral with the indicator case. The oil temperature indicator shall be of an electro-mechanical design and be labeled in English. A transducer shall be fitted to the OTI that will give a 4 to 20mA milliamp output for the temperature range of the OTI. This shall be wired into the transformer control cubicle. The values of OTI shall not vary by more than plus or minus 30C from the values derived during temperature rise tests. The adjustable contacts listed shall have the following characteristics: Control: Adjustable setting 300C to 1000C Adjustable differential 150C to 300C The OTI shall be calibrated at time of transformer heat run testing in accordance with manufacturer’s instructions. The supplier shall use a type of temperature probe that shall be subject to NIE approval.

3.4.6 Fibre Optic Connected Temperature Measurement Fibre optic connected temperature sensors shall be installed within the first transformer of each type, unless indicated otherwise by NIE Networks at time of tender, to facilitate direct temperature measurement during type testing. Two fibre optic sensors shall be placed in the hottest part (coil) of each winding of the centre phase. The final position of the sensors will be agreed following design review, to facilitate direct measurement of the winding temperature. The tenderer shall take care not to introduce excessive layers of insulation at the position of the fibre optic sensor/s, which could introduce measurement errors.

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The fibre optic cables shall be terminated external to the transformer main tank so as to allow the connection of an external measuring device. The tenderer shall provide details and cost options for suitable equipment capable of connecting to the fibre optic terminations. The tenderer shall provide details of the fibre optic connected sensors to be used and the method of calibration to be applied prior to factory testing. 3.5 Control cubicle

3.5.1 General The weatherproof control cubicle shall be made of suitable over painted stainless steel, to be supplied and mounted on the transformer tank. The cubicle shall accommodate all local controls for coolers and tap-changer and provide terminals for bushing current transformers. The degree of protection of the control cubicle shall be a minimum of IP54 of BS EN 60529. The control cubicle shall be constructed and mounted so as to ensure that all work can be completed at ground level. The cubicle shall be placed a minimum of 600mm from ground level and shall take into consideration the required bending radius of any connected cables. In addition, the height of the cabinet shall be restricted to minimize the need to work at height of greater than 2metres. The cubicle box shall have a hinged door suitable for locking with an 8mm shank padlock and shall be mounted on the transformer tank using anti-vibration mountings. An internal lamp controlled by a door switch shall be provided. Approximately 10% spare terminals shall be provided in the control cubicle. The cubicle shall also house the winding temperature control devices and serve as a marshalling point for wiring associated with cooling control, alarm and trip circuits etc. Its degree of protection, anti-condensation, illumination facilities and locking arrangements shall be the same as for the tap-changer mechanism box. It shall be possible to view the WTIs through a vandal proof window on the cubicle without having to open the cubicle door/s. The vandal proof window shall be made of suitable material to minimse the effect of UV light related degradation. A connection drawing to NIE approval shall be fixed inside the kiosk. All multicore cables and WTI capillary tubes shall enter from a gland plate located in the base of the control cubicle. Sufficient space shall be available to facilitate the installation of a fibre optic winding temperature sensor measurement device, see Clause 3.4.6.

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A single-phase switched outdoor type-3 power socket rated at 13 Amps shall be fitted on the outside of the cubicle. In addition, a three-phase switched power socket rated at 13 Amps shall be fitted on the inside of the cubicle. Internal wiring shall comply with the NIE Networks specification 211-03.

3.5.2 Control cubicle internal temperature The cubicle shall be fitted with an anti-condensation space heater, which shall be controlled as follows: (1) A humidistat with an adjustable operating range. (2) A cut-out thermostat with an adjustable operating range, to prevent overheating. These circuits shall operate at 230V, 50Hz.

3.5.3 Cubicle equipment The following devices shall be installed in the cubicle: (1) Winding temperature indication (2) Top oil temperature indication. (3) Appropriately labeled facilities for manual control of the fans/pumps. (4) Motor protection circuit breakers (5) Links for testing of winding temperature indicating device. 3.6 Tank and accessories

3.6.1 General The tank shall be suitably constructed so as to minimise the possibility of rupture following internal failure, see Clause 3.6.5. The tank construction shall be such as to prevent water from lodging or pooling on it. An adequate number of inspection and maintenance access hatches shall be provided on the top and sides of the main tank. The number of hatches shall be agreed with NIE Networks as part of the transformer design review. The transformer shall rest on anti-vibration supports to avoid transmission of vibration, see Clause 3.10.

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Dome nuts are to be fitted on all external studs. All studs are to be coated with anti-corrosive wax based lubricant. Alternatives to nebar type gaskets shall only be used following agreement with NIE. The tenderer shall provide details of the grade of gasket to be used at the time of tender.

3.6.2 Tank vacuum and pressure The Tender shall state the maximum vacuum/internal pressures which the main tank and tap-changer diverter switch enclosures are designed to withstand. Details of the maximum pressures and valve connection positions shall also be clearly embossed on a label fitted to the tank wall for the purposes of site operations, see Clause 3.11. If the tap-changer diverter switch or combined diverter and selector switch enclosure is inside the main tank, it shall be so designed that, in the event of full vacuum being applied to the main tank, no oil can leak from the diverter switch (or combined diverter and selector switch) enclosure.

3.6.3 Conservator tank A conservator tank shall be provided and it shall be in two separate sections so as to prevent cross communication of oil compartments. One section will supply oil to the main transformer tank; cable boxes, link boxes and tap-change selector, and the other section will supply oil to the tap change diverter switch oil compartment. Each separate section of the conservator shall have an oil level gauge, which shall be so located that it can easily be read by a person standing at ground level. The range of indicated oil level shall correspond to average oil temperatures from -10oC to 80oC and the position for the oil level at 15oC shall be indelibly and clearly marked, bearing the inscription '15oC Oil Level'. The use of rubber conservator bags/bladder is not acceptable. Permanently fixed conservator tank filler pipes shall be installed to facilitate topping up of oil from ground level. The filling pipes shall be equipped with adequate intermediate supports to remove the risk of tank to pipe interface (weld) failure, which could result in the loss of oil. In addition the filler pipe shall be fitted with a combination of non-return and gate valves. The conservator tank and its supports shall have adequate capacity to facilitate the movement of oil from the main tank to its associated conservator during maintenance activities.

3.6.4 Breathers The section of the conservator tank supplying the main transformer shall be fitted with a

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regenerative type breather. The regenerative breather, electrical controls, timers etc. shall be located at ground level. The section of the conservator tank supplying the diverter switch oil compartment shall be fitted with an approved desiccant type breather or an alternative regenerative type breather. The breather and electrical controls, timers, etc. shall be located so that maintenance can be carried out at ground level.

3.6.5 Pressure relief device Pressure relief devices with 2 alarm and 1 trip contact, which are set to open on excess pressure, and to reseal automatically shall be fitted to the main tank. They shall be located to ensure that discharge does not cause danger to personnel. The pressure relief shall be designed as appropriate to minimise the probability of tank rupture should an internal failure occur. The proposed method of design calculation and illustrations shall be available at time of tender.

3.6.6 Low oil level device A low oil level device with alarm contacts set to close on low oil level and to reseal automatically on restoration of oil level, shall be fitted to the section of the conservator tank supplying the main transformer and to the section of the conservator tank supplying the diverter switch oil compartment.

3.6.7 Oil sampling points 2" BSP oil sampling devices shall be fitted for taking oil samples from the top and bottom of the main tank and from the tap-changer diverter oil compartments. Sampling points shall be accessible to a person standing at ground level. Additional oil sampling points shall be available as detailed in Clause 3.6.15 to facilitate the connection of on line oil sampling devices.

3.6.8 Oil filtration and vacuum processing Two 2" filter valves shall be fitted to the tank, one on the top and the other diagonally opposite on the bottom. Two 2" BSP bore filter valves shall be fitted to the tap-changer compartment, one on the top and the other on the bottom so that the oil can be filtered effectively. If separate banks of cooling radiators are supplied, two 2" BSP filter valves shall be fitted to each bank.

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Threaded portions of valves shall be appropriately protected by captive covers.

3.6.9 Lifting lugs Lifting lugs shall be provided for supporting the weight of the transformer including core, windings, fittings and with the tank filled with oil. Lugs shall be supplied for tap changer, cooler structure where appropriate, main tank cover and other such compartments as necessary.

3.6.10 Jacking pads Four jacking pads shall be provided near the corners to the tank of the transformer and approximately 700mm above the lowest part of the tank. These pads shall be designed to take the complete weight of the transformer filled with oil.

3.6.11 Hauling eyes Hauling eyes shall be provided on all sides of the transformer.

3.6.12 Earthing terminals Earthing terminals shall be provided close to each of the four corners of the tank to facilitate earthing of the transformer by NIE Netwoks. Earthing terminals shall be provided with 2 of 14mm diameter holes for fixing bolts. A similar arrangement shall be provided on cooler structures if appropriate.

3.6.13 Oil valves All oil valves shall be lockable in the open and closed positions. The use of loose fittings to lock valves in the open or closed positions, other than a pad lock, is not acceptable. They shall clearly indicate whether they are in their open or closed positions and shall be fitted with appropriate blanking plates. All oil valves shall be made of brass. All oil valves shall have padlocking facilities, able to accommodate a padlock with 38mm square body and with a 7mm-diameter shackle having a clear inside width of 20mm and an inside length of 16mm to 30mm. The holes provided for the shackle shall not be less than 8mm diameter.

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Additional lockable oil valves fitted to the top and bottom of the transformer tank side wall shall be provided to facilitate the connection of oil monitoring equipment, see Clause 3.6.15.

3.6.14 HV neutral CT accommodation Provision shall be made for the tank mounting of an external neutral bushing type CT. This shall be located in a suitable position to allow for a connection to be made between the CT terminal and the transformer HV bushing neutral terminal.

3.6.15 On-line transformer condition based diagnostics The manufacturer shall make provision for the mounting of transformer on-line diagnostic monitoring equipment. Additional facilities shall be available to facilitate connection to a spare MCB within the main control cubicle. Consideration will be given for the provision of on-line diagnostics for the transformer main tank, tap changer and HV bushings. On line condition monitoring of the transformer shall be offered as an option, if specified in Schedule A. The on line monitoring shall be on a continuous (24 hour/365 days a year) basis.

3.6.16 Ancillary and control cable installation Cable trays used for the purpose of secondary cabling e.g. fan and motor supplies, WTI cables, etc. shall be made of suitable stainless steel. Consideration shall be given to the appropriate mounting of stainless steel materials so as to prevent an influence from other materials. Clips and/or cable ties made of plastic shall not be used to secure ancillary or control cables in position. NIE Networks will however accept plastic backed metal ties.

3.6.17 Removable access covers (Inspection hatches) Removable covers on the tank required to facilitate access for the connection of bushings, tap changers, test links, etc shall be of adequate size to ensure ease of access for staff and to facilitate use of any tools during installation and repair activities. Additional removable covers on the top of the tank shall be provided to facilitate inspection of the core and windings. Details of NIE Networks requirements shall be agreed at time of tender. Removable covers shall weigh no more than 25kgs to facilitate ease of manual handling. All removable covers shall be suitably labeled.

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3.7 Transformer oil

3.7.1 General The insulating oil shall be Class 1 mineral oil to BS 148 or BS EN 60296. The complete first filling shall be new oil provided by the Supplier. The use of anti-oxidant is not permitted. It is not acceptable to supply oil for the purpose of topping up the transformer in plastic containers.

3.7.2 PCB The oil shall not include polychlorinated biphenyls (PCB), polychloroterphenyls (PCT) or polychlorobenzyltoluene (PCBT). The material used for the transformers, such as insulating materials, varnishes; paints etc. shall also not contain PCB, PCT or PCBT. The concentration of PCB shall be less than the detection limit of the measurement method specified in IEC 60997. 3.8 Gas relays and sampling device

3.8.1 Gas operated relays A double float relay fitted with two sets of normally-open alarm/and trip contacts (i.e. 2 x alarm and 2 x trip) shall be provided in the pipe connection from the main tank to the oil conservator tank. Operation shall be such that a slow release of gas closes an alarm circuit while a sudden pressure rise results in the operation of both alarm and trip circuits. NIE Networks will require evidence that the particular equipment is suitably adapted and rated for the transformer offered. It shall be possible to apply compressed air at ground level to the relay for the purposes of testing. A gas pressure relay shall be mounted in the pipe leading from the tap-changer diverter switch compartment to the oil conservator tank. This shall be fitted with two sets of NO trip contacts. It shall be possible to apply compressed air at ground level to the relay for the purposes of testing.

3.8.2 Gas sampling device The gas release connection from the gas relay shall be brought down to a gas sampling device, which shall be accessible to a person standing at ground level. A test connection from the gas relay shall be brought to the gas sampling device, if suitable, or

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may be terminated beside it. Isolating valves shall be provided in both the gas sampling and test connections. These valves shall be accessible to a person standing at ground level. The gas sampling device shall have the following facilities: (a) Gas connection from the gas relay through an isolating valve on the gas sampling device (b) Coupling in the pipe connections to enable the device to be removed from the transformer. (c) Gas sampling valve at the top, with outlet approximately 3mm diameter to make rubber tube connection. The outlet shall have a captive screwed cap. (d) Oil drain valve at the bottom with blanking plug. (e) The oil level in the device shall be visible from the front. 3.9 Bushings, link boxes and terminals

3.9.1 General The high voltage windings, phases and neutral, low voltage windings phases and the tertiary windings phases shall be brought out through fully rated bushings.

All oil filled CT chambers shall be provided with suitable means of venting air and draining oil. Any valves provided for the purposes of draining oil shall be lockable, see Clause 3.6.13.

3.9.2. Bushings HV, LV and tertiary outdoor bushings shall comply with BS EN 60137 and shall be fully rated for the transformers normal and overload capability. Preference shall be for condenser type HV bushings where the central conductor does not involve the passage of oil from transformer tank to top of bushing. All condenser type bushings shall be fitted with a test tap. In addition, an embossed label shall be fitted to the bushing flange, which clearly states its capacitance in picofarads (pF) and the tan δ (loss angle) value in percent (%). All bushings shall be grey in colour. Composite type bushings shall be fitted with test tap and preferably have alternate long-short profile sheds. Minimum creepage distances for outdoor bushings shall be in accordance with the 'heavily polluted atmosphere' category of BS EN 60137 and IEC 60815. This shall be based

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upon a minimum specific creepage distance of 31kV/mm, system highest voltage of 300kV, 123kV, 24kV and the appropriate shed diameter factor, kD. 275kV HV bushings shall be of the draw lead top connected type. All bushings shall be fitted with lightning rod gaps.

Oil filled LV bushings, if offered, rated 36kV and above shall be fitted with oil-level gauges of the window type, clearly readable from ground level. All bushings shall be mounted on turrets to facilitate installation of CTs and minimise the amount of oil, which must be removed from the transformer to facilitate bushing changes. 110kV bushings shall be of the draw rod connected type. Draw rod connected bushings shall be designed so as to minimize the possibility of the rod bottom connection being misaligned or over tightened during the installation or removal of a bushing. Any lowering of the oil required to carry out bushing installation or removal shall not expose the transformer core and/or windings. The bushings shall have minimum ratings, as detailed in Table 11 below. Winding Voltage rating (kV) Minimum rating (amps) CT provision

HV 300 800 Yes LV 123 2000 Yes

Neutral 36 Fully rated bushing insulator (N.B. bushing rating to include for 50% short term

overload)

-

Tertiary 36 2000 - Table 11 Bushings minimum ratings and CT requirement

Method statements shall be provided for the purposes of installation and removal of bushings. Lifting brackets required for the installation and removal of bushings shall be provided with the first transformer. The lifting brackets shall be clearly stamped with their safe working load and supplied with appropriate test certificates. The following 275kV and 110kV bushing loading options shall be available as shown in Table 12. Please note the cantilever test loads are not detailed below, however they should comply with BS EN 60137. Options Voltage Cantilever Operating Load

1 110kV 2000N 2 110kV 4000N 3 275kV 4000N 4 275kV 6000N

Table 12 Minimum withstand values of Cantilever Load The transformer tank shall be suitable constructed to meet the requirements of forces that may

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potentially be applied to any of the bushing options detailed in Table 12.

3.9.4 Clearances The minimum design clearances for outdoor air insulated bushings shall generally be in accordance with BS EN 60076-3, unless as detailed below in Table 13. In addition, creepage distances shall be in accordance with IEC 60815 for heavily polluted conditions. System Voltage Phase-to-phase (mm) Phase-to-earth (mm) 275kV 2800 2100110kV 1600 110022kV 700 500 Table 13 Clearances

N.B. NIE Networks require the above minimum clearances to meet the requirements of NIE Networks safety rules and UK standards whilst allowing for an increase of electrical clearances for the fitting of bus bar clamps.

3.9.5 Current Transformers Provision shall be made for mounting current transformers in each of the HV bushing turrets as detailed in Table 14 below. Bushing Rated Voltage

(kV) Internal diameter (mm)

External diameter (mm)

Axial Length (mm)

HV 275 440 820 640 LV 110 320 520 620 Table 14 CT Mounting Requirements Accommodation for 2 neutral CTs in each phase connection, mounted internally, at the HV neutral end shall be provided. The neutral CT requirements shall be detailed in Schedule A. Test current terminals using 660V bushings shall be mounted externally on the transformer tank adjacent to the neutral CTs. The test current terminals shall be internally connected to facilitate the application of test current through the primary side of the neutral CTs. HV, LV and Neutral current transformer secondary terminal boxes shall be fitted. Provision shall be made for the mounting of an externally mounted CT to be fitted between the HV neutral and earth, see clause 3.6.14. An LDC CT shall be installed on the LV 'l2' phase and shall be as specified in Schedule A. This shall be in accordance with BS EN 60044-1, with an accuracy of Class 1.0 and an extended

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current rating of 150% of the rated primary current.

3.9.6 Neutral and Tertiary Terminal Location NI Networks require 3 options as detailed below in Table 15. The final requirements will be detailed in Schedule A. Option Neutral and Tertiary Location 1 The neutral connection shall be at the left hand side of the main tank and tertiary

connection at the right hand side of the tank when viewed looking from the HV terminal side of the transformer.

2 The neutral connection shall be at the right hand side of the main tank and tertiary connection at the left hand side of the tank when viewed looking from the HV terminal side of the transformer.

3 Provision for mounting neutral and tertiary connections at either end of the transformer. Table 15 Neutral and Tertiary Terminal Location

3.9.7 Terminals The HV terminals shall be round copper as follows: 275kV bushings 40mm diameter x 150mm long 110kV bushings 40mm diameter x 150mm long 22kV bushings 40mm diameter x 150mm long

3.9.8 Terminal markings The HV, LV and Tertiary terminals shall be identified with NIE Networks practice as detailed in Table 16. Terminals Identifier HV L1, L2, L3 LV l1, l2, l3 Tertiary L11, l12, l13 Table 16 Terminal Markings When facing the terminals the phase markings shall be high voltage - L1, L2, L3. Low voltage – l3, l2, l1 from left to right.

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LV SIDE HV SIDE

l1 L1

l2 L2

L3 l3 The spacing of the H.V. and L.V. bushings shall be as for a set of three arranged about the centre-line of the transformer. These markings shall be clearly and permanently shown on the cover plate and on the sidewalls of the main tank below each HV bushing location and also to the left hand side of LV cable boxes. 3.10 Noise and vibration Transformers and auxiliary plant shall be designed and manufactured to reduce noise and vibration. A low noise option shall be available. The sound pressure level of transformers shall not exceed the levels detailed in Table 17. Cooling arrangement Standard transformer Low Noise Transformer Oil Natural cooling 60dB(A) 57dB(A) Air Forced cooling 65dB(A 62dB(A) Table 17 Noise levels All measurements shall be guaranteed by the Supplier and shall be taken in accordance with BS EN 60076-10. To minimise the affects of ground and structure borne vibration, anti-vibration mountings shall be provided between the transformer base and the foundations. The mounting arrangement shall: (i) Take cognizance of the irregularities in the tank under-base and the plinth surface, (ii) be of an oil and weather resisting material comprising either a rubber or other approved compound, capable of operation at temperatures between minus 10oC and 80oC, (iii) have a total unloaded depth (excluding load spreader plates) not exceeding 40mm, (iv) at 100Hz, have an attenuation of at least 32 dB (assuming an infinite ground impedance value) when loaded, at room temperature, to the same pressure as in service.

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3.11 Labels and rating plates

3.11.1 General All markings including labels, rating and diagrams plates and instructions shall be clear, indelible and in English. Cast-in, moulded or embossed words other then in English shall be covered with a permanently fixed non-ferrous label inscribed in English. Painted markings are not acceptable.

3.11.2 Rating plate A rating plate in accordance with BS EN 60076 shall be fitted. This shall include the additional information in items (s), (t), (u) and (w) of Clause 5.2 of BS EN 60076, Part 1. The plate shall be so designed that by means of a hinged section or otherwise, the connection diagram for each alternative vector group is displayed when the links specified in Clause 2.6 are positioned as appropriate.

3.11.3 Locations of valves and air release cocks A plate showing the locations and normal positions of all valves and air release cocks or plugs shall be provided. This plate shall incorporate a warning to operators to refer to the Maintenance Instructions before applying vacuum treatment to the tank.

3.11.4 Gas points Labels shall be attached to all gas release, gas sampling and gas test points stating the name of the associated oil compartment.

3.11.5 Direction of rotation The direction of rotation of operating handles and motors shall be clearly marked.

3.11.6 Control and auxiliary equipment All control and auxiliary equipment in the cooling system marshalling kiosk and in the tap-changer mechanism box shall be clearly labelled. The cooling fans and pumps and their associated MCB’s shall be labelled with matching

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numbers.

3.11.7 400V connections All mechanism boxes, marshalling kiosks etc. containing 400V connections shall have a label bearing the inscription: "DANGER 400 VOLTS" permanently fixed to the outside of doors or covers. Internal 1-phase and 3-phase wiring to motors (fans, pumps, tap changer), heaters and lighting shall comply with BS 7671 amendment 3, and shall be coloured brown for the 3 phases and identified as L1, L2, L3 and blue for the neutral and identified as N. Alternatively the phases and neutral shall be coloured as detailed in Table 18. Wiring type Phase Colour Neutral Colour 1-phase Brown Blue 3-phase Brown, Black Grey Blue Table 18 Connections

3.12 Safety features The design of transformers shall be such as to minimize the requirement to work at heights. However, for those tasks where this cannot be avoided, suitable fall prevention systems shall be provided, in compliance with The Work at Height Regulations (NI) 2005, see Appendix 1.

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Section 4. Cleaning and painting

4.1 General Transformers may be exposed to coastal atmospheric conditions and therefore must be able to resist the corrosive effects of the environment. All fixings and fastenings used in the fabrication of the transformer shall be of suitable material or treated to the same performance level as the tank to prevent corrosion, having regard for the corrosion effects of different adjacent materials. The painting and corrosion protection system proposed by the Manufacturer is subject to approval by NIE Networks. A full description of the proposed system shall be given including surface preparation, rust inhibition, paint thickness, treatment of bolts, nuts, threads etc. 4.2 Surface preparation 4.2.1 Prior to painting, all ferrous surfaces shall be thoroughly blast cleaned and free from rust scale and other contaminants. Ferrous exterior surfaces which are to be blast cleaned shall, before any treatment, meet rust grades A, B, or C as specified in BS EN ISO 8501-1. Unless otherwise agreed between Purchaser and Supplier, blast cleaned surfaces shall be coated within 4 hours without outside exposure. 4.2.2 Cleaning of the external surfaces of radiators and other components where complete access to surfaces is restricted by their construction, shall be achieved by submersion in a suitable cleaning solution. 4.2.3 The filling of imperfections in metallic surfaces by the use of powder or plastic fillers is not permitted. 4.2.4 The internal oil surfaces of coolers and radiators shall be flushed with oil. The flushing oil shall be filtered to ensure that any dislodged metallic particles are removed. Pipework is to be cleaned internally. 4.2.5 Special attention shall be given to items, which are to be hot-dip galvanised to ensure the removal of welding slag etc. not readily removed by normal cleaning methods, which would otherwise prevent the retention of the galvanised coating.

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4.3 Surface Protection 4.3.1 Surfaces which are in contact with oil, shall not be galvanised, zinc sprayed or cadmium plated. 4.3.2 Other ferrous surfaces shall be treated by one of the following methods: - 1) Hot dip galvanised in accordance with BS EN ISO 1461. The zinc coating shall be smooth, clean and of uniform thickness free from defects. The preparation for galvanising and the galvanising process itself shall neither adversely affect the mechanical properties of the coated material nor result in distortion. 2) Sprayed with zinc applied by the flame gun process, and the thickness of zinc deposited shall not be less than 100 micrometers minimum local thickness in accordance with BS 2569-2. Radiators shall be hot dip galvanised to BS EN ISO 1461. 4.4 Coating systems The treatment and protective coating of the transformer shall comply with BS 5493:1977. The coating shall be according to the 'Long' category, typically 10 - 20 years as defined in Section 2, 'Life required of coating'. As defined in Table 1 of BS 5493, 'Environment and special situations', the category shall be 'polluted coastal' (Table 3, Part 3).

4.4.1 Painting 4.4.1.1 The metallic surfaces of components and fittings, which have been blast, cleaned and are to be continuously immersed in oil, shall have their surfaces sealed by a single coat of oil resistant paint or resin. 4.4.1.2 The interior surfaces of all compartments containing insulating oil shall be provided with a light colour paint protective system, in accordance with ENA TS 98-1, Table 1 Scheme No 1. 4.4.1.3 The interior surfaces of the control cubicle and air-filled chambers shall receive a paint protective system in accordance with ENA TS 98-1 Table 1 Scheme No2. The final coat shall be of light coloured anti-condensation finish. 4.4.1.4 The external surfaces of the transformer, including radiators, tap-changer and control cubicle shall be provided with a paint protective system in accordance with ENA TS 98-1, Table 1 Scheme 3. The colour of the final coat shall be to colour reference Cement

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Grey to RAL shade 7033. 4.4.1.5 Fixings and fastenings used in fabrications shall be of suitable material or treated to prevent corrosion, having regard for corrosion effects of different adjacent materials. 4.4.1.6 Damage occurring to any part of a coating system shall be made good to the same standard of corrosion protection and appearance as that originally employed, to the satisfaction of the Purchaser. Painting on site shall not be undertaken in inclement weather. 4.4.1.7 The supplier shall supply details of their quality system concerning the materials used, type and routine quality control and type tests, together with full details of the proposed surface preparation schemes and coating systems including numbers of coats, paint specifications, dry film thickness and tolerances. 4.5 Inspection Inspection shall be carried out in accordance with BS 5438 Section 4 Table 8 and clear and adequate records of inspection as defined in paragraphs 39-43 shall be provided. 4.6 Other requirements The interior of the conservator and any tank internal surfaces above oil level shall be given a coat of oil-resisting paint and varnish. Fixing studs for access covers shall be coated with a wax based rust inhibitor paint to facilitate cover removal. In addition, captive nuts shall be installed upon exposed studs so as to minimise the potential for corrosion to occur. The interior surfaces of the control cubicle and all air-filled chambers shall receive a minimum of one priming coat, an undercoat and a finishing coat of paint applied to the thoroughly cleaned metal. The final coat shall be of a light coloured anti-condensation finish.

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Section 5. Tests 5.1 General Tests shall be carried out on each transformer in accordance with BS EN 60076 and as specified below. NIE Networks shall have the right to reject a transformer if test results do not comply with the standards/values specified and information/data preferred in the tendered schedules. Before and after each acceptance test and as indicated within this specification, samples of oil shall be taken from the transformer and analysed for dissolved gases using the procedures specified in BS EN 60567 and BS EN 60599. Results of the analysis of gases dissolved in the oil shall be immediately submitted to NIE Networks and included in the Acceptance Test Report. In the event of a test failure all testing shall be dis-continued until a sequence of re-testing is agreed with NIE Networks. All information relating to the failure, including type/routine test data and cause of failure shall be provided to NIE Networks. 5.2 Type tests The following shall be regarded as type tests and shall be carried out on the first transformer of each rating, as detailed in Table 19.

Type Tests Relevant Standards Temperature rise BS EN 60076-2 Measurement of zero sequence impedance BS EN 60076-1

Table 19 Type tests Notes on Type tests: 1. Test of temperature rise (BS EN 60076-2). This test shall be carried out on the tap having maximum losses. Temperature rise shall be measured at ONAN rating and at the full load rating. 2. Determination of winding temperature before shutdown– (BS EN 60076-2) Measurement of hot winding resistance shall commence within 90 seconds of shutdown inclusive of generator run down time. 3. The temperature rise tests shall be confirmed upon the first transformer using fibre optic connected temperature sensors. The sensor shall be brought to a suitable termination flange on the outside of the transformer, which will facilitate the connection of data recording equipment.

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5.3 Routine tests The following routine tests shall be performed on each transformer.

Routine test

Relevant Standards

Measurement of winding resistance at all taps* BS EN 60076-1 Measurement of voltage ratio BS EN 60076-1 Voltage vector relationship BS EN 60076-1 Measurement of impedance voltage at all taps BS EN 60076-1 Measurement of short circuit impedance BS EN 60076-1 Measurement of zero sequence impedance BS EN 60076-1 Measurement of load loss BS EN 60076-1 Measurement of no-load loss & current (including harmonics)

BS EN 60076-1

On-load tap changer BS EN 60076-1 Induced overvoltage power frequency withstand BS EN 60076-3 Lightning impulse BS EN 60076-3 Separate source power frequency withstand BS EN 60076-3 Partial discharge measurements BS EN 60076-3 Applied voltage to all auxiliary circuits BS EN 60076-3 Tests on bushings BS EN 60137 Tests on fans and pumps Tests on painting and galvanising BS 5493 Measurement of acoustic sound level BS EN 60076-10

Table 20 Routine tests * Please note BS EN 60076-1 states that the winding resistance shall be carried out at the mid point and extreme tappings; however NIE require measurements to be provided for all tap positions. Notes on Routine tests: 1. Lightning impulse tests are to be full wave impulse voltage withstand tests and also include chopped-wave tests (BS EN 60076-3 clause 13) as follows: -

• 1 reduced full impulse • 1 100% full impulse • 1 or more reduced chopped impulses • 2 110% chopped impulses • 2 100% full impulses

Note: In carrying out impulse tests, the two extreme taps and the principal tap shall be used with each phase being tested on a different tap unless previously agreed with NIE following analysis of the winding RSO test results. 2. Induced overvoltage, separate source voltage and lightning impulse tests shall be carried

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out at the relevant voltages specified in Clause 2.8. 3. Tests on on-load tap-changer to be when fully assembled on transformer. Tests to include operation across complete tap range. 4. Noise level measurement to be in accordance with BS EN 60076-10 using a precision sound level meter conforming to BS EN 61672. Any deviation from the tests required in this specification and from IEC test requirements shall only be carried out following prior consultation and written agreement with NIE. 5.4 Special tests The following special tests may be required by NIE and agreed at time of Tender and should be included as option costs.

Special Tests

Relevant Standard

Short circuit withstand BS EN 60076-5 Additional temperature rise test at 1.3 p.u. BS EN 60076-2 Over excitation capability to be confirmed during transformer tests

Benchmark tests: 1. SFRA - Frequency response analysis (Doble) 2. Recovery voltage test 3. Bushing DLA to be tested before and after high voltage testing (Doble). 4. Winding capacitance test (Doble) 5. Infra red images to be captured during ONAN and ONAF/OFAF operation.

To be agreed with NIE

Table 21 Special Tests 5.5 Site tests If the contract includes the complete range of site work the following tests on site shall be carried out after plant is fully assembled:

Site Tests Ratio and vector group checks. Insulation resistance (between windings and windings to earth). Oil tests; Moisture content and breakdown voltage. SFRA tests

Table 22 Site tests

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The Supplier shall provide all necessary test equipment and personnel under the Contract and shall be responsible for calibration of instruments, where required, and shall supply to NIE Networks three copies of the reports on site tests. Should the contract exclude assembly of the transformer on site by the supplier, the above tests will be carried out by NIE's staff under the general direction of the Supervisor mentioned in Clause 6.2. 5.6 Test certificates Routine, type and special test certificates shall be forwarded to the Asset Management Operational Manager, NIE Networks, Fortwilliam House, Edgewater Office Park, Edgewater Road, Belfast, BT3 9JQ. Test certificates shall include relevant details and calculation methods. In the case of lightning impulse tests, copies of the response shall be attached and in the case of temperature rise tests, the extrapolation curves shall be provided. 5.7. Witnessing of tests It shall be necessary for a representative of NIE Networks to witness the Temperature Rise tests, Impulse Voltage Withstand Tests, including chopped waves, (if required), and all other Type Tests and Routine Tests at the manufacturer's works, on the first transformer of each size and type required on any order. Not less than 20 days notice of works tests shall be given to NIE Networks so that the necessary arrangements may be made by NIE Networks for the attendance of a representative at the works. Arrangements shall be made for as many tests as possible to be carried out during the representative's works visit. NIE Networks reserve the right to have independent witnessing of all type and routine testing.

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Section 6. Packing, installation, manufacture and training 6.1 Packing and prohibited materials Accessories shall be packed in non-returnable cases or crates with protection against damage by water, transport and outdoor storage. Each case shall have a detailed packing note and be clearly marked on the adjacent sides and top with NIE Networks order number, transformer serial number and gross weight. Certain packing materials such as straw, peat-moss litter, grain, etc., are prohibited by Government regulation. Goods packed in prohibited material will be refused. 6.2 Installation and assembly The transformer (including a separate cooling bank if applicable) shall be installed on a foundation prepared by NIE Network in strict accordance with drawings provided by the Supplier. The transport to site, which the Contract includes, shall be the responsibility of the Supplier. The contract also includes the provision of a suitably qualified person to supervise the erection and setting to work by the NIE Network staff of the transformers. An extra price shall be quoted for the provision of all staff required to assemble the transformer and prepare it for service. Site staff shall observe NIE Network safety rules at all times. All equipment used for oil handling shall be, to NIE Network satisfaction, certified free from PCB. The Supplier shall prior to tendering fully inform himself of all the requirements and available facilities in regard to transport, route planning, loading/unloading, etc. An outline transport plan shall be submitted with tender. Four months prior to shipping the Contractor shall submit to NIE Network a transport plan that has been agreed with the appropriate Northern Ireland road transport authority. All transport accessories, e.g. riding lugs, jacking pads, blanking-off plates, etc. shall become the property of NIE Networks.

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6.3 Manufacturing programme and progress reports The successful Tenderer shall submit a detailed programme covering the design, manufacture and testing of the transformer within two months of receipt of the NIE Networks official order. He shall subsequently submit reports at intervals as requested by NIE outlining progress and if necessary explaining deviations from programme. NIE Networks shall have the right, subject to prior arrangement, to inspect progress on the order at the Supplier's works.

6.4 Spare parts The Supplier shall give an assurance that spare parts will continue to be available throughout the life of the transformer. A comprehensive list of recommended spare parts with prices shall be included in the attached schedule. This list may be taken into account in tender evaluation. The spare parts recommended shall be clearly identified on drawings which shall be included with the Tender. Spare parts shall be delivered suitably packed and treated for long periods in storage. Each packing shall be clearly and indelibly marked with its contents including a designation number corresponding to the spare parts list in the maintenance instruction. 6.5 Training The supplier shall make provision for NIE Networks staff training and all necessary documentation on the following items: (a) Tap changers and associated control system installation, maintenance and repair. (b) Bushing installation and removal. (c) Cooler installation and removal. (d) Filling of the transformer under full vacuum. 6.6 Drawings and information 6.6.1 The following drawings and information shall be submitted with the Tender: - (a) Overall dimensioned drawings of the transformer. (b) Dimensioned drawings of the main unit arranged for transport. (c) Winding disposition for the transformer.

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(d) Over-excitation curve. (e) Dimensioned drawings of separate cooler banks if applicable. (f) General description of tap-changer, mechanism box, control cubicle, dial

thermometers, gas relays, breathers, fans, pumps etc. (g) Detailed specification of the transformer oil including oxidation inhibitor if

recommended. (h) Details of surface treatment. (i) Outline transport plan. (j) Statement of acceptance of guarantee. (k) Financing details, if applicable. (l) Reference list with particular emphasis on units of similar design and rating. 6.6.2 The following shall be submitted within three months of the Award of Contract: (a) A complete set of final dimensioned drawings for the transformer including details of bushings, tap-changer mechanism box, control cubicle etc. (b) Electrical schematics of the tap-changer control and temperature control protection circuits. (c) Wiring drawings of the tap-changer mechanism box and control cubicle. (d) Pamphlets describing the on-load tap-changer, bushings and auxiliary equipment such as gas relays, dial thermometers, thermostats, fans, pumps etc. (e) Detailed schedule, listing all temperature protection/alarm devices and fan/cooler pump control devices. (f) Detailed dimensioned drawings to enable NIE to design and construct the required foundations for the transformer and cooling bank(s). 6.6.3 With delivery of the transformer, the Supplier shall supply three bound record folders of the technical particulars relating to it. Each folder shall contain the following information: - (a) Technical data. (b) Test Certificates.

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(c) General descriptions. (d) Operation and maintenance instructions. (e) Main drawings.

(f) Pamphlets describing auxiliary equipment such as gas relay, tap changer, etc. 6.6.4 The final drawings shall be forwarded to the Asset Management Operational Manager, NIE Networks, Fortwilliam House, Edgewater Office Park, Edgewater Road, Belfast, BT3 9JQ 3 weeks before delivery of the equipment as follows: - (i) 3 paper copies, and (ii) by one of the following: - (a) CD-ROM Microstation.DGN format (Preferred Option). (b) CD-ROM .DWG format. (c) CD-ROM .DXF format.

7. Quality Assurance And Checks

7.1 The supplier shall be accredited to BS EN ISO 9001 or submit satisfactory evidence to demonstrate that their quality system and inspection procedures are such as to ensure compliance with this standard. 7.2 Samples of different types of conductors and other epoxy coated conductors used in the construction of the winding shall be made available following oven drying for inspection.

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Appendix 1 Compliance with The Work at Heights Regulations (NI) 2005 The design of transformers shall be such as to minimise the requirement to work at heights by, for example, bringing oil bleed pipes and oil top-up points down to low level. Horizontal surfaces on the transformer, where personnel would be expected to stand for work, should be provided with an anti-slip surface coating. Where practical, transformers shall be supplied with suitable edge protection on all sides to enable compliance with The Work at Heights Regulations (Northern Ireland) 2005 No. 279. Edge protection shall be designed to be permanent where possible and removable where clearances cannot be achieved in service. Permanent edge protection shall have the same (or better) resistance to corrosion as the main external components of the transformer and shall have the same life expectancy of forty years or greater. Removable sections of edge protection shall be light-weight for ease of handling and erection and fit for purpose when in position. The dimensions shall be in accordance with Schedule 3 of The Work at Height Regulations (NI) 2005: ‘the top guard-rail or other similar means of protection shall be at least 950 millimetres ---------- above the edge from which any person is liable to fall;’ ‘any intermediate guard-rail or similar means of protection shall be positioned so that any gap between it and other means of protection does not exceed 470 millimetres’ ‘toe-boards shall be suitable and sufficient to prevent the fall of any person, or any material or object, from any place of work’. In addition, it is an NIE requirement that the minimum height to the top of the toe-board shall be 150mm with the bottom edge flush with the top of the transformer tank. A suitable landing position shall be provided to enable ladders to be secured and provide access to the top of the transformer, whilst avoiding the need to walk outside of the guard-rail protected work area or on vulnerable areas of the transformer such as cooler fins. A suitable gate or similar solid mechanism must be provided at access points. If it is demonstrated that full edge protection is not reasonably practicable under Section 6 of The Work at Height Regulations (NI) 2005, due to the physical size of the transformer or due to obstacles preventing the erection of edge protection, then a suitable fall-arrest system must be provided. This system shall have an anchorage point a minimum of 1.8 metres above the standing surface and as vertical as possible to the standing surface to avoid the pendulum effect. This anchor point(s) for the fall arrest systems should be designed for the attachment of two persons.

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SCHEDULE A (To be completed by Purchaser) General particulars of definite work

1 2 3 4 5 6 7

8

9

10

11

12

13 14

Section(s) for purposes of payments and taking over Site of Station Number of Units required Continuous maximum rating MVA Rated higher voltage between phases kV Rated lower voltage between phases kV HV termination details: LV termination details: NIE Networks Maximo No.(s) Condition based monitoring fitted Auxiliary supplies Fans, pumps, heaters etc. Control & protection LV winding l2 phase LDC CT details HV Bushing Differential CTs

(i) CTs required? (ii) CT details

Online monitoring

A

Various Sites

240 275 110

Outdoor Bushings

Outdoor Bushings

TBA

YES/NO?

400/230V a.c.

110V d.c.

Class 0.5, 50VA, ratio 1200/2, ext 150% (to be confirmed)

YES/NO? Ratio 600/1,Class X, Vk = 700V, Ie =

50mA, Rct ≤ 1.2 ohms (to be confirmed)

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SCHEDULE B (to be completed by Purchaser) Commencement date and dates of readiness for inspection, testing, delivery, access to site and completion definite work Commencement Date

1 2 3 4 5

Section(s) for purposes of payment(s) and taking over Site of Station Times from Commencement Date: Within which detailed drawings shall be submitted for approval Calendar Months Within which the material shall be ready for inspection and testing Calendar Months Within which the Contractor will require access to the site Calendar Months Within which the material shall be delivered to site Calendar Months Within which the works shall be completed, tested and ready for continuous use Calendar Months

A Various sites

B Various sites

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SCHEDULE C (to be completed by Purchaser) Access facilities to the site

1 2 3 4 5 6 7 8

Section Site of Station Ordnance Survey Grid Reference (O.S. NORTHERN IRELAND 1:50000 Sheet ) Whether direct road access is available to site Approximate distance from the site to the nearest road Whether transport by rail is required Whether there is a railway siding near to the site Whether there are any known transport restrictions in the immediate locality of site

A Various sites Yes

mts No No None

B Various sites Yes

mts No No None

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SCHEDULE D (to be completed by Supplier)

Guaranteed rated values and characteristics

SECTION A 240MVA TRANSFORMER

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SCHEDULE D (to be completed by Supplier) Guaranteed rated values and characteristics Manufacturer ................................................................................................ 1. Maximum continuous ratings in MVA ONAN ONAF/OFAF Tap 1 ............. ............. Tap 7 ............. ............. Tap 19 ............. ............. Can the transformer, bushings, tap changer and connections be safely overloaded in accordance with latest edition of IEC 60076-7....................................... 2. Losses in kW TAP 1 TAP 7 TAP 19 No-Load Loss ......... ......... .......... Load-Loss at 75°C ......... ......... .......... Cooler Motor Losses ......... ......... .......... Total Losses ......... ......... .......... Peak Efficiency ……. ……. ……...

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SCHEDULE D (to be completed by Supplier)

Guaranteed rated values and characteristics 3. Impedance voltage, no-load ratio and nominal current IMPEDANCE NO-LOAD RATIO NOMINAL CURRENT VOLTAGE % (......../33kV) (ONAF/OFAF) Tap 1 ............. ............. .............. Tap 2 ............. ............. .............. Tap 3 ............. ............. .............. Tap 4 ............. ............. .............. Tap 5 ............. ............. .............. Tap 6 ............. ............. .............. Tap 7 ............. ............. .............. Tap 8 ............. ............. .............. Tap 9 ............. ............. .............. Tap 10 ............. ............. .............. Tap 11 ............. ............. .............. Tap 12 ............. ............. .............. Tap 13 ............. ............. .............. Tap 14 ............. ............. .............. Tap 15 ............. ............. .............. Tap 16 ............. ............. ............. Tap 17 ............. ............. .............. Tap 18 ............. ............. .............. Tap 19 ............. ............. ..............

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SCHEDULE D (to be completed by Supplier) Guaranteed rated values and characteristics 4. Zero sequence impedance SHORT OPEN CIRCUIT CIRCUIT Zero sequence impedance in ohms HV Winding .......... .......... LV Winding .......... .......... Tertiary Winding …….. ……… 5. Core Number of limbs .......................... Number of wound limbs .......................... Cross-section area of (a) wound limbs .......................mm² (b) non-wound limbs .......................mm² (c) yoke .......................mm² Type of steel and sheet thickness .......................... Total weight of steel .........................t Flux density at rated voltage .....................Tesla Magnetising current on principal tap .....................A(HV)

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SCHEDULE D (to be completed by Supplier) Guaranteed rated values and characteristics 5. Core Maximum permissible overfluxing expressed as a percentage of rated volts/HZ, on any tap. ON NO-LOAD ON FULL-LOAD Continuously ........... ............ For 1 minute ........... ............ For 10 seconds ........... ............ 6. Windings Positioning from core outwards Core /....................... Type of winding, e.g. layer, disc HV ......................... Regulating ......................... LV ......................... Tertiary…………… Cross sectional area of conductor HV ......................mm² Regulating ......................mm² LV ..............................mm² Tertiary………………mm² Total weight of copper .................................... Type of insulating paper ....................................

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SCHEDULE D (to be completed by Supplier) Guaranteed rated values and characteristics 7. Noise level Guaranteed noise levels according to BS EN 60076-10 Complete Transformer at ONAN ..........................dB(A) Complete Transformer at ONAF/OFAF ..........................dB(A) Cooling bank only ..........................dB(A) 8. Partial discharge Expected background level .............................pC Expected value at U2 = kV .............................pC 9. Tap changer Manufacturer and type ................................ Number of Compartments ............................... Current rating ............................... Overload rating (Continuous) …………………… Number of taps ............................... Lightning impulse withstand level ........................kV peak Power frequency withstand level ......................kV r.m.s. 10. Oil Supplier and type ................................... Specification ................................... Method of delivery to site ................................... Is an oxidation inhibitor recommended? ...................................

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Recommended concentration ................................... SCHEDULE D (to be completed by Supplier) Guaranteed rated values and characteristics 11. Bushings HV LV NEUTRAL TERTIARY Manufacturer ......... ......... ......... ……….. Type Number ......... ......... ......... ……….. Creepage distance ......... ......... ......... ……….. Electrical clearance ......... ......... ......... ……….. Current rating …….. …… ……. ……….. 12. Vacuum withstand Tank ...........................Pa Radiators ...........................Pa Conservator ...........................Pa Tap change compartment ...........................Pa 13. Impulse tests Are the standard wave-shapes obtainable on all terminals? ............................... If not, what wave-shapes are to be expected? ................................ 14. Pressure relief devices Maker/Type ............................... Number off ............................... Alarm Contacts No. ……….. Trip Contacts No. ……….. 15. Short circuit withstand capability ..............................................................

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SCHEDULE D (to be completed by Supplier) Guaranteed rated values and characteristics 16. Weights Core and windings without tap changer .............................kg Oil in the complete transformer .............................kg Complete transformer ready for service ............................kg Transport unit .............................kg 17. Details of surface treatment ....................................................................................................................... ....................................................................................................................... ....................................................................................................................... 18. Transport dimensions Transport unit length .............................mm Transport unit width .............................mm Transport unit height .............................mm 19. Overall dimensions Length overall .............................mm Width overall .............................mm Height overall .............................mm Signed : ..............................................

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For and on behalf of : ................................ Date : ................................................

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SCHEDULE D (to be completed by Supplier)

Prices and delivery SECTION A

240MVA TRANSFORMER

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SCHEDULE D (to be completed by Supplier) Prices and delivery *State currency

SECTION A * Firm Price

.…... transformers rated ...240... MVA complete - with oil, etc. in accordance with this Specification including all routine tests specified ............ Cost including transport delivery, placing on prepared foundation, supervision of assembly and testing on site ........... Extra cost of providing all appropriate staff, cranes, fitters, etc. required for assembly and site testing of one 275/110kV transformers. ........... Extra cost of type test on one 276/110kV transformers ........... . Extra cost of heat run test on one 275/110kV Tx transformers ...........

Tender valid until .............. ...........

Signed : .............................................. For and on behalf of : ................................ Date : ................................................

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SCHEDULE E (to be completed by Supplier) Price schedule of recommended spare parts * State currency

QUANTITY DESCRIPTION * TOTAL PRICE

Signed : .............................................. For and on behalf of : ................................ Date : ................................................

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SCHEDULE F (to be completed by Supplier) Schedule of deviations from specification

Signed : .............................................. For and on behalf of : ................................ Date : ................................................

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