TECHNOLOGY TO THE FORE
SWITCHGEARC O M P L E X
More than 9500 Crompton Greaves CapacitiveVoltage Transformers
upto 420 kV have been putinto service in various environments in
manycountries all over the world since 1984 wherethey are operating
satisfactorily.
Our CVTs adhere to the requirements of theInternational quality
standards and our quality andenvironment management systems are
certified toISO 90012000 and ISO 14001 respectively.
DESIGN AND CONSTRUCTION
Figure 1 shows the schematic view as well as theconstruction of
a single stack CVT. Each CVTconsists of a coupling capacitor (CC)
which actsas a voltage divider and an Electro Magnetic Unit(EMU)
which transforms the medium voltage tostandard low voltage.
Depending on the systemvoltage the CC can be a single or a multi
stackunit. The CC and the EMU are individuallyhermetically sealed
to ensure accurateperformance and high reliability.
Coupling Capacitor
The Coupling Capacitor (CC) acts as a voltagedivider and
converts the system voltage to amedium voltage. The active part of
the CCconsists of a large number of oil impregnatedpaper (or paper
and film) capacitor elementsconnected in series. Supercalendered
capacitortissue paper and pure aluminium foils are usedto make the
capacitor elements. The capacitorelements are pressed and held in
insulatingsupports to ensure a stable capacitance evenfor large
temperature variations. The electricalconnections between the
capacitor elements aredesigned for a natural frequency much above
600Hz in order to avoid interference with carriercommunication.
The processed capacitor stack is assembled insidea porcelain
insulator with corrosion resistantaluminium alloy end fittings.
Brown glazedporcelain insulators with shed profile as per
FIG. 1
1 H.V. Terminal 30802 Hood for L.T. Pedestal Mount.
3 Porcelain Flange
4 S.S. Bellow
5 Porcelain Insulator
6 Oil Filling Plug (For EMU)7 Lifting Lugs
8 Secondary Terminal Box
9 Varistor
10 L.V. Terminal Block
11 Gland Plate
12 Surge Arrestor
13 EMU Tank
14 Oil Sampling Valve
15 Earthing Pads
16 Compensating Choke
17 M.V. Tap Terminal
18 Oil level Indicator (For EMU)19 NHF Terminal
20 Tank Cover
21 Bellow Level Indicator
22 Chamber For Indicator
23 Earthing Switch (Optional)24 Drain Coil (Optional)
CAPACITOR VOLTAGE TRANSFORMER
2221
1
2
3
4
5
C1
C2
67
8
23
924
Name plate
10
11
12
13
20
19
18
17
16
15
14
FD
F
S ESLink
1a1n2a2nfgN
Link
vZa
LTr
NHF
C2
C1
A
AR
CIN
G D
ISTA
NC
EH
H
AR
CIN
G D
ISTA
NC
E
IEC 815 are used. The insulators are cemented toaluminium alloy
flanges for improved strength. Oilvolume changes due to temperature
variations arecompensated by a stainless steel bellow installedat
the upper end of the CC. The unit is completelyfilled with degassed
insulated oil under vacuum.The bellow is pressurised by inert gas
(from thetop surface) to maintain a positive oil pressureeven at
lowest ambient temperatures. The CVTthus has very low PD levels
even at low ambienttemperatures.
Electromagnetic Unit
The Electromagnetic Unit (EMU) consists of amedium voltage
transformer, compensating reactor,damping element and surge
protection device. Theunit is housed inside a steel tank which is
filledwith insulating oil leaving a largely dimensioned aircushion
at the top in order to take care of changesin the oil volume due to
fluctuations in the ambienttemperature. An oil level indivator is
mounted onthe side wall of the tank.
The CC unit is mounted on the EMU tank and theinsulated earth
terminal of the CC (marked asNHF in Fig.1) is also accessible for
connecting topower line carrier communication equipment. Asurge
arrester across this terminal and earthserves as the surge
protection device. The NHFterminal must always be connected to
earth if theCVT is not connected to carrier equipment.
The secondary terminal box is provided on the EMUtank. Secondary
leadouts, NHF lead and earthleads are all terminated inside the
secondaryterminal box. The EMU is caliberated and adjustedat
factory for all burden and accuracyrequirements. No site
adjustments ormeasurements are neccessary. The EMU isgiven adequate
surface treatment for corrosionprotection for life long
service.
MAINTENANCE
The product is self contained, maintenance freeand requires no
spares over its entire life span.We recommend regular and periodic
checks asper pre-specified schedules (specified in theInstruction
Manuals supplied with the CVTs).
FIG. 3
OPTIONALS / ACCESSORIES
Terminal Connector (Aluminium/Bimetallic, NEMA or as per
customer specs)
Three element Carrier Protection Device Level (comprising Drain
Coil, surge Arrester & Earth Switch)
Cable Glands
OIL LEVEL INDICATOR ON EMUBELLOW POSITION INDICATOR
BOTTOM VIEWBOTTOM VIEW
A - HV TerminalC1 - Pri. CapacitanceC2 - Sec. CapacitanceNHF -
HF TerminalL - Compensating ChokeTr - Intermediate Voltage
TransformerF - HRC FuseZd - Damping DeviceV - VaristorD - Drain
CoilS - Surge ArestorES - Earthing SwitchN - Neutral Terminal
Of
Intermediate Transformer
FIG. 2
W
W
A
W
W
A
1. TYPE DESIGNATION : UNIT CVE CVE CVE CVE CVE CVE CVE CVE
2. APPLICABLE STANDARDS : IEC 186 (1987) IEC 358 (1990)
3. HIGHEST SYSTEM VOLTAGE : kV 72.5 123 145 170 245 300 362
420
4. ONE MIN POWER FREQUENCY VOLTAGE : kV 140 230 275 325 460 510
570 630
5. LIGHTNING IMPULSE : kVp 325 550 650 750 1050 1175 1300
1425
6. SWITCHING IMPULSE : kVp NA 850 950 1050
7. RATED FREQUENCY : Hz 50/60
8. AMBIENT TEMPERATURE : C -25 TO 50
9. SEISMIC ACCELERATION : g 0.3/0.5
10. RATED VOLTAGE FACTOR : 1.2 (CONT) / 1.5 (30 SEC)
11. ONE MIN. POWER FREQUENCYVOLTAGE ON SECONDARY
: kV 3
12. SECONDARY VOLTAGE : V 100, 100/3, 110, 110/3 , 120 , 120/
3.13. TOTAL CREEPAGE DISTANCE : mm 1810 3075 3625 4250 6125 7500
9050 10500
14. EQUIVALENT CAPACITANCE : pF 8800 6000 6000 6000 4400 4400
4400 4400
15. TOTAL SIMULTANEOUS BURDEN / ACCURACY : 200VA / CL 0.5*
16. TOTAL THERMAL BURDEN : VA 500VA 750VA
17. CANTILEVER LOAD : kg 125 200 250
18. ARCING DISTANCE : mm 820 1215 1215 1415 1930 2180 2630
2830
19. TOTAL HEIGHT (H) : mm 1950 2350 2350 2550 3410 3655 4175
4370
20. MAXIMUM DEPTH (A) : mm 785 785 785 785 785 785 850 850
21. MOUNTING DIMENSIONS (W) : mm 450 450 450 450 450 450 450
450
22. TOTAL WEIGHT : kg 315 360 430 450 575 600 810 825
23. QTY OF OIL : kg 75 90 95 100 115 125 200 210
24. OIL VOLUME COMPENSATION (CC UNIT) : STAINLESS STEEL
BELLOW
*THE ABOVE ARE TYPICAL VALUES. OTHER SPECS. ARE ALSO
FEASIBLE.
Power SystemsA Business Unit of Crompton Greaves Ltd.
Data subject to change Cat.No. CVT-112 (6/04/3K)
Switchgear ComplexA-3, MIDC, Ambad, Nashik - 422 010 IndiaTel :
(+91) 253 2301105 to 110 (Dir.)Fax : (+91) 253 2381247, 2382219
(Dir.)E-mail : [email protected] :
www.cglonline.comRegd. Office : 6th Floor, CG House,Dr. Annie
Besant Road, Worli, Mumbai - 400 030, India.
OPTIONALSTYPE DESIGNATION : UNIT CVE CVE CVE CVE CVE CVE CVE
CVE
1. HIGHEST SYSTEM VOLTAGE : kV 72.5 123 145 170 245 300 362
420
2. VOLTAGE FACTOR : - 1.9 FOR 30 SEC
3. CREEPAGE DISTANCE : mm/kV 25, 31, 35 25
4. TOTAL SIMULTANEOUS BURDEN / ACCURACY : - 200 VA / CL 0.2 100
VA /CL 0.2
