Cables - Ts 5 Test Standard Uground Cable Networks

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ETSA Utilities, ABN 13 332 330 749, a partnership of:

CKI Utilities Holdings Pty Ltd, ABN 54 091 142 380.

HEI Utilities Holdings Pty Ltd, ABN 50 091 142 362.

CKI/HEI Utilities Distribution Pty Ltd, ABN 19 091 143 038.

each incorporated in Australia CKI Utilities Development Limited,

ABN 65 090 718 880. HEI Utilities Development Limited,

ABN 82 090 718 951. each incorporated in The Bahamas

Copyright © 2007

TESTING STANDARD

FOR

UNDERGROUND & OVERHEAD NETWORKS

TECHNICAL STANDARD TS-105

Refer to TS-105 Appendix A for all the standard forms that are relevant to testing and are a pre-requisite to ETSA Utilities

acceptance of the “Certificate of ETSA Utilities Electrical Compliance” REVISION NOTICE

DATE EXPLANATION

Mar 07 Added clauses 2.1.4 & 2.7 & Table of Contents. Modified clause 1.1, 1.9, 2.2.3, 2.3.3, 2.3.4 & 3.2.

Issue : March 2007

Technical Standard TS-105

Issue: March 07 Authorised by: J Ali Date: 26/03/07 Page 1 of 10

Terms and Conditions refer www.etsautilities.com.au

CONTENTS 1.0 GENERAL ............................................................................................... 2 2.0 UNDERGROUND TESTING ................................................................ 2

2.1 LOW VOLTAGE XLPE DISTRIBUTION CABLES .................................. 2

2.1.1 Insulation Resistance................................................................................. 2 2.1.2 Phasing Test .............................................................................................. 3 2.1.3 Continuity Test (resistance of bolted connections)................................... 3 2.1.4 Earth Resistance Test ................................................................................ 3

2.2 PUBLIC LIGHTING CABLE CIRCUITS .................................................... 4

2.2.1 Insulation Resistance Testing.................................................................... 4 2.2.2 Polarity Checking...................................................................................... 4 2.2.3 Electrical Testing ...................................................................................... 4

2.3 11 kV and 33 kV XLPE CABLES Including CBD Cables............................ 4

2.3.1 Phasing Test ............................................................................................. 4 2.3.2 Outer Sheath Insulation Resistance (Screen wire test) ............................. 4 2.3.3 HV test on XLPE cables after Installation ............................................... 5 2.3.4 Alternative HV Test Requirement on Insulation for 11kV Cables ........... 6

2.4 PAPER INSULATED CABLES...................................................................... 6

2.4.1 General ...................................................................................................... 6 2.4.2 Tests on LV Cables ................................................................................... 6 2.4.3 Test on 11kV and 33kV Cables between Cores and Earth ....................... 6

2.5 66 kV OIL FILLED CABLES (Refer to the transmission cable manual for specific circuit information)............................................................................. 7

2.5.1 Core to Sheath Test after Repairs.............................................................. 7 2.5.2 Outer Sheath Integrity Test ....................................................................... 7

2.6 66 kV XLPE CABLES (Refer to the Transmission Cable Manual for specific circuit information)............................................................................. 7

2.6.1 Safety......................................................................................................... 7 2.6.2 Core to Sheath Test after Repairs.............................................................. 7 2.6.3 Outer Sheath Integrity Test ....................................................................... 7

2.7 CABLE IDENTIFICATION TESTING......................................................... 8

3.0 OVERHEAD TESTING ......................................................................... 9 3.1 LV ABC ............................................................................................................. 9

3.2 BURIED SWER EARTHING CABLE CIRCUITS...................................... 9

3.3 11kV and 33kV COVERED CONDUCTOR and 11kV IUC........................ 9

3.3.1 General ...................................................................................................... 9 3.3.2 Phasing Test .............................................................................................. 9




1.0 GENERAL 1.1 This Instruction is applicable to any new extension or repair and replacement

work.

1.2 The purpose of performing cable tests is to prove that the circuit is safe to energise or commission. Cable testing does not necessarily indicate the condition or remaining life of a circuit.

1.3 Isolating and earthing requirements for cables connected to transformers and switching devices are contained in the Switching Operators Handbook.

1.4 During single phase switching, ferroresonance conditions can be avoided in loaded cable circuits by switching at the transformer location.

1.5 The test work area shall be defined with a red tape barrier and warning signs.

1.6 High Voltage commissioning tests on new URD cables shall be performed without connection to other equipment.

1.7 All tests shall be performed on individual sections of HV cable. Separate sections of HV cable shall not be connected in series and tested as a whole.

1.8 All test results shall be recorded in accordance with Appendix A.

1.9 All low and high voltage cables must have the point of destination clearly labelled at both ends. As an example;

Low voltage isolator: Destination is the lot number and street name for the first service pillar.

High voltage switch: LB1 to transformer eg, LB1 to LB1 TC xxxxxx

Refer to E-1943 Sheet 7.11 for cable naming and labelling details.

1.10 The basis for any numbering sequence for any electrical equipment is to look at the equipment from the kerb and circuit one is on the left side of the equipment and any identification sequence is undertaken in a clockwise direction.

For example for a three way pillar the incoming low voltage circuit as shown on the plan on the left side is circuit one the centre circuit is two and the right side circuit is three.

The cable destination needs to also reflect the FINAL destination.

2.0 UNDERGROUND TESTING 2.1 LOW VOLTAGE XLPE DISTRIBUTION CABLES

The low voltage cables must be tested in the following sequence:

2.1.1 Insulation Resistance

2.1.1.1 Cables shall be tested for insulation resistance with an insulation tester (i.e. Megger) at 1000 Volts for 1 minute.

2.1.1.2 The minimum insulation resistance to earth or between phases shall be 100 meg-ohms.

2.1.1.3 The instrument used for this measurement shall have a minimum resolution of 10 meg-ohms on the 0 to 500 meg-ohm range.




2.1.1.4 At the conclusion of LV insulation resistance testing, the neutrals must be connected to the earth stakes.

2.1.2 Phasing Test

2.1.2.1 The correct phasing of all LV circuits shall be checked at all positions where the LV cables are terminated into fuse bases and where any LV cable is run from point to point.

2.1.2.2 This test shall be performed with an instrument designed for the purpose. Mains frequency voltage of 240 Volts is not acceptable for this test.

2.1.2.3 The neutral conductor shall be connected to the earth stake for this test.

2.1.3 Continuity Test (resistance of bolted connections)

2.1.3.1 For loop LV UD systems, a continuity test shall be carried out on each LV circuit to ensure that all bolted connections are complete and adequate. The test shall be carried out as follows:

(i) At the transformer firmly bond all 4 conductors together

(ii) Undertake a continuity test at every point where there is a service provision or open point. In a fused service pillar the bottom row of fuses bases must be the point at which the test is undertaken as that is the furthest extent of the ETSA network.

2.1.3.2 The difference between the readings of each phase conductor and the neutral for each individual test shall not be greater than 10% of each other. Any difference greater than this may indicate a loose or dirty connection and will require further investigation.

2.1.3.3 The instrument used for this measurement should have a resolution to the second decimal point in the 0 to 5 ohm range. A typical instrument would be the earth “Megger” type and taking into account the resistance values of the test leads.

2.1.4 Earth Resistance Test

MEN Areas

In any overhead or underground network the earth resistance at any point along the length of a LV feeder is to have a maximum resistance of 10 ohms prior to connection to the existing network. In difficult earthing locations, alternative configurations may be utilised with agreement from the relevant ETSA Utilities Manager, as detailed in TS-109 (currently in DRAFT format and to be issued shortly).

CMEN Areas

In any overhead or underground network the overall resistance to earth shall be less than 1 ohm prior to connection to the existing network.




2.2 PUBLIC LIGHTING CABLE CIRCUITS

2.2.1 Insulation Resistance Testing

The insulation resistance of public lighting circuits, including columns wired on site, shall be tested in accordance with clause 2.1.1 above.

2.2.2 Polarity Checking.

A visual check at each end of public lighting circuits shall be carried prior to commissioning.

2.2.3 Electrical Testing

The earth and neutral are to be left disconnected at the point of supply. The earth and neutral are to be individually meggered at 250 Volts.

The neutral and earth can be bolted up if testing is satisfactory.

Check the active by meggering the active back to the point of supply.

Check the P/L column and assembly. Apply 250 Volts to the load side of the fuses at the column. Different types and sizes of luminaries have different characteristics.

Any variation from the normal consistent readings for the same type of luminaire indicates a problem in the connection or PL fitting.

Any reading that is greater then this may indicate an open circuit problem.

Any reading that is lower then this may indicate a fault on the load side of the fuse.

On completion the active conductor should be well clear of any metal components in the column

2.3 11 KV AND 33 KV XLPE CABLES INCLUDING CBD CABLES

New cables shall be tested individually, ie one phase at a time and one section at a time.

2.3.1 Phasing Test

2.3.1.1 The correct phasing of all HV circuits shall be checked at all positions where the HV cables have been terminated.

2.3.1.2 This test shall be performed with an instrument designed for the purpose. 240 Volt mains frequency is not acceptable for the performance of this test. The test may be conducted on either the wire screens or the aluminium conductors.

2.3.1.3 Where the test is performed on the wire screens, they shall be disconnected from earth.

2.3.2 Outer Sheath Insulation Resistance (Screen wire test)

2.3.2.1 The purpose of the test is to determine soundness of the outer polyethylene sheath against water ingress, mechanical damage and termite attack.

2.3.2.2 Values below 0.5 meg-ohms (500 kΩ) can indicate sheath damage. Values between 1.0 and 10 meg-ohms may not indicate damage in a single location. Fault finding can often be




very difficult. In new cables, values of greater than 100 meg-ohms is required.

2.3.2.3 The integrity of the outer sheath shall be checked after cables have been buried by an insulation tester (Megger) at 1000 Volts. The test shall be conducted for 1 minute between each wire screen and earth after the cable has been jointed and terminations installed.

2.3.2.4 For cables after repairs, the resistance must not be less than 10 meg-ohms.

2.3.2.5 Where HV cable circuits are cut and joined to new circuits, sheath testing must be carried out on the existing old circuit prior to jointing to the new cable.

2.3.3 HV test on XLPE cables already in service or previously energised

EXCEPT FOR NEW CABLES, TESTING AT VOLTAGES GREATER THAN 5.0 kV IS NOT PERMITTED

Studies carried out on DC high voltage testing of XLPE cables now conclude that;

• DC testing above 5kV of field aged XLPE cables generally increases water tree growth and reduces service life.

• 5kV is not considered a “High Voltage DC Test”

(References; EPRI Reports, IEEE Standards and Olex Cables - NZ)

The test voltages for tests on XLPE cables is now limited to 5kV after in service repairs and 10kV for new installations. A 5kV Megger is suitable for a 5kV test on cables after repairs. The changes to this section will also make it possible for a repaired cable to be tested by repair crews and made available for immediate return to service.

Application Test Voltage Criteria After repairs – Sheath 1kV Megger 1 minute 10 meg-ohms min.

After repairs - Insulation 5kV Megger 1 minute or 5kV DC 1 minute

1000 meg-ohms min. 5.0 μA (micro-amps) max.

2.3.4 HV test on new XLPE cable

2.3.4.1 Prior to the performance of this test, the screen wires must be connected to the permanent earth position.

2.3.4.2 The cable shall be tested at the test voltage and the pass criteria shall be in accordance with the following table:

Application Test Voltage Criteria

New cables – Sheath 1kV Megger 1 minute 100 meg-ohms

New cables – Insulation 10kV DC 15 minute or 10kV DC 15 minutes

1.0 μA (micro-amps) max. 1000 meg-ohms min.

Note: A “new” cable installation is one not previously connected and

energised to any existing network asset.




2.3.4.3 If further repair works are undertaken, and they require additional joints to be installed, the complete HV testing procedure shall be repeated.

2.3.5 Alternative HV Test Requirement on Insulation for 11kV Cables

Where it is not practical to conduct a high voltage test, the test requirements for insulation (core to screen wire) may be limited to testing for the condition of “safe to energise”.

The following list of circumstances and conditions must be met as a minimum requirement:

(a) The work conditions shall be emergency or as determined by ETSA Utilities’ Project Manager,

(b) The cable circuit voltage shall be 11kV,

(d) The circuit outage duration shall be not more than 48 hours,

(e) The work shall involve extending or repairs to existing circuits,

(f) The insulation test shall be applied for 1 minute between each phase core and screen with a 1000 Volt minimum insulation tester (Megger),

(g) Typically the test result should be in the order of 1000 meg-ohms.

2.4 PAPER INSULATED CABLES

2.4.1 General

Tests on paper insulated cable systems shall be performed after new installations, extensions or repairs.

Many CBD high voltage cable circuits are connected to older style equipment and therefore test voltages are purposely reduced from those in Australian Standard AS1026.

2.4.2 Tests on LV Cables

An insulation resistance test shall be conducted with a 1000 Volt megger. Test results as low as 10 meg-ohms on old cable circuits are common and therefore considered safe to energise.

2.4.3 Test on 11kV and 33kV Cables between Cores and Earth

For three core belted cables, the test on any core shall be conducted between the core and lead sheath with the remaining two cores connected to earth. The test voltages and pass criteria shall be in accordance with the table below.

Application Test Voltage Criteria 11kV new cables 5kV Megger 1 minute 1000 meg-ohms 11kV after repairs 5kV Megger 1 minute 100 meg-ohms 33kV - no TF’s connected 5kV Megger 1 minute 1000 meg-ohms 33kV - with TF’s connected 5kV Megger 1 minute 15 meg-ohms




2.5 66kV OIL FILLED CABLES

2.5.1 Core to Sheath Test after Repairs

After repairs have been carried out on 66kV single core oil filled cables, a DC test shall be applied between the conductor core and metallic sheath (earthed). The test voltage shall be 60kV DC for 15 minutes.

The cable shall be considered safe to energise if the test voltage is maintained without failure for the duration of the test. The leakage current at the end of the test shall be recorded.

2.5.2 Outer Sheath Integrity Test

An insulation resistance test between the aluminium sheath and earth shall be conducted. Where the cable construction includes an anti-termite metallic barrier, that barrier shall be connected to the aluminium sheath and the insulation test performed to earth.

The test voltage applied for 1 minute shall be 5kV DC applied with either a high voltage test set or insulation resistance tester (Megger).

2.6 66kV XLPE CABLES

2.6.1 Safety

Careful attention to safety procedures must be carried out. Rope barriers and warning signs are particularly important when testing 66kV cable circuits.

2.6.2 Core to Sheath Test after Repairs

After repairs have been carried out, the 66kV XLPE cable shall be energised at power frequency for 24 hours without load.

DC testing is not permitted.

The cable sheath link box/cross bonding system shall be put into its normal condition.

2.6.3 Outer Sheath Integrity Test

An insulation resistance test between the metallic sheath and earth shall be conducted. The anti-termite barrier must be connected to the metallic sheath and the insulation test performed to earth.

The test voltage applied for 1 minute shall be 5kV DC applied with either a high voltage test set or insulation resistance tester (Megger).




2.7 CABLE IDENTIFICATION TESTING

Whenever any work is performed on cables that are installed in an ETSA Utilities transformer or switching cubicle the relevant personnel will undertake the following in accordance with the current Network Access Procedure:

1. Locate the labeling at each end of each cable and note what is recorded on the label.

• If the labels match and identify each cable as being the same phase, proceed to step 2.

• If the labels do not match, all cables MUST be traced and the correct identification confirmed.

2. All cables are to be proved dead and earthed before continuing with the testing.

3. Perform a phase identity test.

4. Perform a screen to earth and screen to core test for high voltage cables and a Megger test for low voltage cables in accordance with clause 2 of this standard.

5. The test results will be written up on the relevant forms in TS-105 Appendix A, F-34 (HV) / F-31 (LV) in duplicate.

6. If cable test results on the existing cable/s are unsatisfactory, then the damage to the cable/s is to be identified & repaired. The Contractor’s NAP will be withheld until the damaged cable/s is rectified, then re-issued when satisfactory cable test results are available.

In the event that the cable identification tests are performed as a Request for Network Access (RNA) then:

• The original of the test results will be supplied to the contractor along with the NAP at the site handover.

• The cables to be worked on for the period of the contractor’s access will be earthed. It will be the contractor’s responsibility to arrange for earths to be removed and cables disconnected at both ends for the purpose of cable testing.

• The contractor MUST be present for the site handover of any ETSA Utilities assets.




3.0 OVERHEAD TESTING 3.1 LV ABC

New LV ABC circuits shall be tested (Meggered) for insulation resistance between cores and earth prior to commissioning to prove safe to energise and confirm that all earths have been removed.

Any cores not being tested are to be earthed including the neutral.

The neutral bond must be connected after the test.

3.2 BURIED SWER EARTHING CABLE CIRCUITS

A visual check of cable connections is only required prior to the reinstatement of trenching. Refer to E1451 and E1453 for construction details.

3.3 11KV AND 33KV COVERED CONDUCTOR AND 11KV IUC

3.3.1 General

A conductor covering insulation test is not required.

3.3.2 Phasing Test

HV covered conductors shall be tested for correct phasing in accordance with existing procedures for bare conductor systems.

New and repaired HV ABC circuits shall be tested (Meggered) for insulation resistance prior to commissioning to prove safe to energise and confirm that all earths have been removed.

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Cables - Ts 5 Test Standard Uground Cable Networks