Hv Double Pole Isolator Traction Power Transformer Type


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HV DOUBLE POLE ISOLATOR

TYPE: Manually operated single or Double break

upright mounting with the movement of blade(s)

in a horizontal plane with or without earthing

switch and suitable for outdoor installation

No. of pole

Two/Three

Nominal system voltage

132kV

220kV

Highest system voltage

145kV

245kV

Rated current

1250A

1250A

Rated short time withstand 31.5kA 31.5kA (rms)

current for one second

(rms)

Isolating distance in air

1800mm 2800mm

HV CURRENT TRANSFORMER

TYPE: Single phase, Oil filled, Self cooled,

Outdoor Type

Rated system voltage

132kV 220kV

Frequency

50Hz. ±3%

Rated primary current

400-200 200-100

Rated secondary current

5A

5A

Rated burden Class of isolation

30VA A

30VA A

HV CIRCUIT BREAKER (CB)

Rated system voltage 132kV

220kV

Rated normal current 1600A

2000A

Rated short circuit

40kA

50kA

breaking current

Rated breaking capacity 5800MVA 12250

MVA

Frequency

50Hz

1

TRACTION POWER TRANSFORMER

TYPE: ONAN cooled, single phase, step down Power

transformer, Double limb wound, Core Type

Outdoor installation

Winding

Uniformly insulated

concentratric

Frequency

50Hz

Rated primary voltage

132kV OR 220kV

Rated secondary voltage 27kV

Rated power

21.6/30 MVA

30/42 MVA

System

25kV LIGHTING ARRESTER Single phase ac traction

Nominal system voltage
Rated frequency

25kV (phase to earth) possible variation in the traction supply 22.5 to 27.5 kV sometimes touching 30kV 50Hz

Type Line discharge class

Non-linear metal oxide resistor type without gap CLASS 3

Continous operating 35kV (rms) voltage capability

25kV POTENTIAL TRANSFORMER (PT)

Type

I

II

PTR

27.5Kv/100V 27.5kV/110V

Burden

30VA

100VA

25kV CURRENT TRANSFORMER (CT)

TYPE

OCT – 47 AD/01

CTR

1500/750/5A

Burden

60VA

Insulation Level

35/250kV

2

DYNAMIC REACTIVE POWER COMPENSATION

EQUIPMENT ( DRPC)

System

Single phase ac Traction System

Nominal system

25kV (phase to earth)

voltages

Rated frequency

50Hz

25KV AC SINGLE POLE ISOLATOR (SPI) AND DOUBLE

POLE ISOLATOR (DPI)

Type

Manually operated, horizontally mounted on

pole, vertical break type and suitable for outdoor

Number of phases No’s of pole Isolating distance Rated voltage Rated current

One
Single pole/double pole 500mm (min.) in air
25kV (nominal) 30kV max. Type –I 1250A (used at SSP & SP) Type –II 1600A (used at FP & TSS)

25kV INTERRUPTER

System

Single phase ac traction system

Nominal system

25kV variation from 19kV to 27.5kV

voltage

– occasionally touching 30kV

Rated frequency

50Hz ±3%

No. of poles

One

Class

Outdoor

Rated voltage class 52kV

Rated normal current 800A

Rated short circuit 20kA (peak)

making current

25KV CIRCUIT BREAKER (CB)

System

Single phase ac traction system

Rated system voltage 25kV

Rated normal current 1600A

Rated short circuit 20kA

breaking current

Rated breaking

550MVA

capacity

Rated Frequency

50 Hz

AUXILARY TRANSFORMER (AT)

Type

Double wound, single phase, ONAN

cooled, step down transformer for

outdoor installation.

Rated voltage of

a) Nominal voltage 25kV

primary winding

b) Minimum voltage 19kV

c) Maximum voltage 27.5kV

Rated voltage of secondary winding Rated frequency Rated Power at rated nominal voltage

240V
50Hz ±3% 5kVA, 10kVA, 25kVA and 100kVA

Voltage Regulation
The permissible variation of the bus bar voltage on the busbars at the grid sub-station is +10% and -5% i.e., between 27,500 V. and 23,750 V. The tappings on the transformers are on the secondary winding and are set to ensure that the voltage is maintained as high as possible but not exceeding 27.5 kV at the feeding post at any time.

3

4

Rating Of Equipments At Traction Sub-Staion with 30/42MVA Power Transformer

Sr. Name of Equipment 1. 132kV Double pole Isolator 2. 132kV Current Transformer 3. 132kV Circuit Breaker 4. 132kV Potential Transformer 5. 132kV Lightning Arrester 6. 132kV Bushing CT 7. Traction Transformer
8. 25kV Bushing CT 9. 25kV Lightning Arrester 10 25kV Current Transformer 11. 25kV Circuit Breaker 12. 25kV Single pole Isolator 13. 25kV Potential Transformer type-II 14. Series Reactor 15. Shunt Capacitor 16. NCT 17. 25kV Potential Transformer type-I 18. 25kV Bi polar Isolator 19. 25kV Interruptor

Rating 1250A 400-200/5A 1600A 132kV/110V 120kV 600/5A 132kV/25kV, 30/42MVA 3000/5A 42kV 1500-750/5A 2000A 3150A 27.5kV/110V 875 kVAR 7700kVAR 4/2/1A 27.5kV/100V 1600A 2000A

Feeding and Sectioning Arrangements

 The generation and transmission systems are 3-phase systems. The singlephase traction load causes unbalance in the supply system. This unbalance has undesirable effects on the generators and equipment of other consumers, if its value becomes excessive.
 The permissible voltage unbalance at the point of common coupling on the grid supply system should not exceed the following limits:—
5

Voltage Unbalance (%)

Instantaneous

5

2 hours

3

Continuous

2

 To keep the unbalance on the 3-phase grid system within the above limits, power for ac single-phase traction is tapped off the grid system across the different phases at adjacent sub-stations in cyclic order.

TSS Bus-bar layout
 The bay widths are standardized for each primary voltage i.e. 66 kV, 110kV, 132 kV and 220 kV.
 The most generally used system voltage is 132 kV and bay widths for 132 kV are standardized as 14.0 m for HV bay and 6.0 m for 25 kV bay.
 The stung bus on the HV side stung at a height of 9.35 m from ground level comprises of 54/3.18 mm (28.62 mm dia) ACSR conductor (Zebra) with a gross area of aluminium of 428 mm2.
 On the 25 kV side 50 mm outside dia. aluminium tubular bus bar is provided at a height of 3.8 m.
 Tension of stung bus is specified as 450 kgf and the earth screen wires as 200 kgf at 4°C without wind.
 The maximum span from the last tower to sub-station gantry is generally limited to around 75 m.
 If the distance of the incoming HV transmission line from the grid sub-station is more than 4 km, lightning arrestors are provided on the incoming lines, at the traction sub-station.
 The deflections of bus-bars supported on post insulators should not exceed half the diameter of the bus bars or span/1440 whichever is less.
 The current density generally adopted for outdoor copper bus-bars is 2 A/mm2.
 The insulators, bus bars and connections should not be stressed to more than 1/4 of the breaking load or 1/3 of their elastic limit whichever is lower.

6

The minimum clearances in air for live equipment shall be as under:

25 kV

1 Between phases

NA [ since single phase]

2 Between one phase and earth for 500 rigid connection

3 Between any point where man

may be required to stand to the

nearest

a) unsecured conductor in air

3000

b) secured conductors in air

2000

4 Minimum height of bus bar

3800

Clearance in mm 66 110 132 kV kV kV 2000 3000 3000
630 900 1300
3500 3500 4000 3500 3500 4000 4600 4600 4600

220 kV 4000
2100
5000 5000 5500

Characteristics Of Traction Transformers
 To cater for the peaks in the demands, the transformers are capable of withstanding non-recurring over-loads of 50% for 15 minutes and 100% for 5 minutes after the transformer has reached steady temperature on continuous operation at full load.
 Off load tap changing from + 10% to –15% in steps of 5% is provided on the low voltage side. The maximum efficiency is specified at about 50% of full load.
 The temperature rise over an ambient of 50oC for 100% over load for 5 minutes or 50% over load for 15 minutes after continuous full load operation is specified not to exceed 50oC for winding (resistance measurement) and 40oC for oil by thermometer.
 The transformers of ratings of 21.6 MVA are specified as ONAN cooled and so designed that with ONAF cooling at a later date the capacity is capable of being increased by 40% more by provision of forced cooling (ONAF).
7

Winding And Oil Temperature Protection
 The life of the transformer depends upon the state of its insulation, whose rate of deterioration is accelerated at excessively high temperatures. Therefore, the transformers have been provided with winding and oil temperature alarm and tripping device which operate through mercury contacts. The settings adopted for the above are :

Winding temperature
alarm 100°C

Winding temperature
tripping 105°C

Oil temperature
alarm 85°C

Oil Temperature
tripping 90°C

Earth Resistance
 At each power supply installation, an earthing system shall be provided. The combined resistance of the earthing system shall be not more than the following values:-

S.N. Name of the station
1. Traction substation 2. Switching station 3. Booster transformer station 4. Auxiliary transformer station

The limit of combined earth resistance in Ohm 0.5 2.0 10.0 10.0

Earth Electrodes
 The earth electrode shall normally be of mild steel galvanised perforated pipe of not less than 40 mm nominal bore, of about 4 m length provided with a spike at one end and welded lug suitable for taking directly MS flat of required size at the other end.
 The pipe shall be embedded as far as possible vertically into the ground, except when hard rock is encountered, where it may be buried inclined to the vertical, the inclination being limited to 30° from the vertical.
 Earth electrodes shall be embedded as far apart as possible from each other. Mutual separation between them shall usually be not less than 6.0 m (which is twice the length of the electrode).

8

 If the value of earth resistance can not be achieved with a reasonable number of electrodes connected in parallel, the earth surrounding the electrodes shall be chemically treated. The earth electrode shall be surrounded in an earth-pit by alternate layers of finely divided coke, crushed coal or charcoal and salt at least 150 mm all round.
 In high embankments, it may be difficult to achieve earth resistance even after chemical treatment of electrodes. In those locations, use of electrodes longer than 4 m so as to reach the parent soil is recommended.
Earthing Arrangement at Traction Substation
Earthing Grid.
 An earthing grid is formed by means of bare mild steel rod of appropriate size buried at a depth of about 600-mm below the ground level and connected to earth electrodes. The connection between the earth electrode and the grid shall be by means of two separate and distinct connections made with 75 mm x 8 mm MS flat.
 The size of the earthing grid conductor shall be decided based on the incoming system voltage and fault level. The fault level considered shall take into account the anticipated increase in fault current during the life span of the station. The size shall be as given below:

Sr.

System

Fault Level (MVA)

Diameter of the grid

Voltage (kV)

conductor (MS rod) in mm

1

66

Upto 4000

32

Above 4000 upto 5000

36

Above 5000 upto 6000

40

2

110

Upto 6000

32

Above 6000 upto 8000

36

Above 8000 upto 10000

40

3

132

Upto 7000

32

Above 7000 upto 10000

36

4

220

Upto 12000

32

Above 12000 upto 16000

36

Above 16000 upto 20000

40

9

Buried Rail
 A steel rail of section 52 kg/m (the one used for the railway track) and length about 13 m shall be buried near the track at the traction substation at a depth of about one metre to form part of the earthing system.
 Two separate and distinct connections shall be made by means of 75 mm x 8 mm MS flat between the earthing grid and the buried rail. The buried rail shall also be connected by means of two separate and distinct connections made of 75 mm x 8 mm MS flat to the rail(s) in a single-rail track circuited section and to the neutral point(s) of the impedance bond(s) in a double-rail track circulated section.
System Earthing.
 One terminal of the secondary winding (25 kV winding) of each traction power transformer shall be earthed directly by connecting it to the earthing grid by means of one 75 mm x 8 mm MS flat, and to the buried rail by means of another 75 mm x 8 mm MS flat.
 One designated terminal of the secondary of each potential, current and auxiliary transformer shall be connected to the earthing grid by means of two separate and distinct earth connections made with 50 mm x 6mm MS flat.
Equipment Earthing.
 The metallic frame work of all outdoor equipments such as transformers, circuit breakers, Interrupters and Isolators, as well as steel structures shall be connected to the earthing grid by means of two separate and distinct connections made with MS flat of size as indicated below; one connection shall be made with the nearest longitudinal conductor, while the other shall be made to the nearest transverse conductor of the grid:
10

Sr. Equipment

System voltage

and fault level

1. Equipments on the

66 kV, upto 3000 MVA

primary side of traction 110 kV, upto 5000 MVA

power transformer.

132 kV, upto 6000 MVA

220 kV, upto 10000 MVA

66 kV, above 3000 upto 6000 MVA

110 kV, above 5000 upto 10000 MVA

132 kV, above 6000 upto 12000 MVA

220 kV, above10000 upto 20000 MVA.

2. Equipments on the

secondary side of

traction power

transformer.

3. Fencing uprights/ steel

structures

4. Doors/ fencing panels

Earthing Inside Control Room.

Ground conductor size 50 mm x 6 mm
75 mm x 8 mm
50 mm x 6 mm
50 mm x 6 mm 6 SWG G.l. Wire

● An earthing ring shall be provided inside the control room by means of 50 mm x 6 mm MS flat which shall be run along the wall at a height of about 300 mm from the floor level. The earthing ring shall be connected to the main earthing grid by means of two separate and distinct connections made with 50 mm x 6 mm MS flat. The earthing ring shall also be connected to an independent earth electrode by means of two separate and distinct connections made with 50 mm x 6 mm MS flat.The metallic framework of control and relay panels, LT A.C. and D.C. distribution boards, battery chargers, remote control equipment cabinets and such other equipments shall be connected to the earthing ring by means of two separate and distinct connections made with 8 SWG galvanised steel wire.

The connections shall be taken along the wall and in recesses in the floor. All recesses shall be covered with cement plaster after finishing the work. Connections between the MS flats shall be made by welding. Earthing of lightning arrester (LA).
● In addition to the earth electrodes provided for the main earthing grid, an independent earth electrode shall be provided for each LA.
11

This earth electrode shall be connected to the ground terminal of the LA as well as to the main earthing grid by means of two separate and distinct connections made with 50 mm x 6 mm MS flat for the 25 kV side LA, and with 75 mm x 8 mm MS flat for the primary side LA. For LA provided for the traction power transformers, there shall also be a connection as direct as possible from the ground terminal of the LA to the frame of the transformer being protected; this connection shall also be made by means of two separate and distinct connections made with 50 mm x 6 mm MS flat for 25 kV side, and with 75 mm x 8mm MS flat for primary side LA.
Earth Screen.
● The area covered by outdoor substation equipments shall be shielded against direct strokes of lightning by an overhead earth screen comprising 19/2.5 mm galvanised steel stranded wire strung across the pinnacles of the metallic structures. The earth screen wires shall be strung at a height as indicated in the approved traction substation layouts (not less than 2.5 m above the live conductors) and shall be solidly connected to the traction substation earthing grid at each termination by means of 50 mm x 6fmm MS flat.
Earthing Of Fencing Uprights And Panels.
● Each metallic fencing upright shall be connected to the traction substation main earthing grid by means of two separate and distinct connections made with 50 mm x 6 mm MS flat. In addition, all the metallic fencing panels shall be connected to the uprights by means of two separate and distinct connections made with 6 SWG G.I. wire. All the metallic door panels shall also be connected to the supporting uprights by means of two separate and distinct connections made with 6 SWG GI wire.
Earthing At The Point Of 240 V Ac 50 Hz Supply For Oil Filtration Plant.
● The 240 V ac 50 Hz distribution board for power supply to oil filtration plant shall be connected to the main earthing grid by means of two separate and distinct connections made with 50 mm x 6 mm MS flat.
Earthing Arrangement at Switching Station
● A minimum number of three earth electrodes (excluding the one to be provided separately for the remote control cubicle earthing) shall be provided at each switching station, and they shall be interconnected by means of 50 mm x 6 mm MS flat forming a closed loop main earthing ring.
12

● This ring shall be connected by two separate and distinct connections made with 50 mm x 6 mm MS flat, to the traction rail in a single-rail track circuited section and to the neutral point of the impedance bond in a double-rail track circuited section of the nearest track, so as to limit the potential gradient developing in the vicinity of the switching station in the event of a fault.
System Earthing.
● One designated terminal of the secondary of each potential, current and auxiliary transformer shall be connected to the main earthing ring by means of two separate and distinct connections made with 50 mm x 6mm MS flat.
Equipment Earthing.
● All masts, structures, fencing uprights, and all outdoor equipment pedestals including auxiliary transformer tank shall be connected to the earthing ring by means of two separate and distinct connections made with 50 mm x 6 mm MS flat. All fencing panels shall be connected to the supporting uprights by means of two separate and distinct connections made with 6 SWG GI wire. All the metallic door panels shall be connected to the supporting uprights by means of two separate and distinct connections made with 6 SWG GI wire.
● The metal casing of CT’s & PT’s shall be connected to the mast/structures by means of two separate and distinct connections made with 50 mm x 6 mm MS flat.
● The ground terminal of lightning arrester shall be connected directly to the earth electrode by means of two separate and distinct connections made with 50 mm x 6 mm MS flat. The earth electrode shall be so placed that the earthing leads from the lightning arrester may be brought to the earth electrode by as short and straight path as possible.
Earthing Inside Remote Control Cubicle.
● An earthing ring shall be provided inside the remote control cubicle by means of 50 mm x 6 mm MS flat; the earthing ring shall be run along the wall on teak wood blocks fixed to the wall at a height of 300 mm from the floor level. The earthing ring shall be connected to the main earthing ring as well as to an independent earth electrode by means of two separate and distinct connections madel with 50 mm x 6 mm MS flat.
13

The metal casing of LT A.C. and D.C. distribution board, battery chargers, terminal board, remote control equipment cabinets and other such equipments shall be connected to the earthing ring by means of two separate and distinct connections made with 8 SWG G.I. wire. The connections shall be taken along the wall and in recesses in the floor. All recesses shall be covered with cement plaster after finishing the work. Connections of earth strips to each other shall be made by welding.
Earthing of Neutral of Local Power Supply System
● At TSS and switching stations where power supply at 415 V/ 240 V, ac, 50 Hz, is taken from the local supply authority and having neutral earth at some distant point in the premises 'of the supply authority, the neutral of such supply shall also be earthed by means of two separate and distinct connections made with 6 SWG G.I. wire by connecting to an independent earth electrode.
Earthing Arrangement at Auxiliary Transformer Station
● The combined earth resistance at an auxiliary transformer station shall be not more than 10 ohm.
● Normally one earth electrode is sufficient for an auxiliary transformer station. The earth electrode shall be connected to the mast on which the auxiliary transformer is mounted by means of two separate and distinct connections made with 50 mm x 6 mm MS flat. In addition the mast shall be connected to the nearest traction rail or to the neutral point of the nearest impedance bond in a double rail track circuited section by means of a 50 mm x 6 mm MS flat.
● The earthing terminal on the transformer tank shall be connected to the mast on which the transformer is mounted by means of two separate and distinct connections made with 50 mm x 6 mm
● MS flat. One terminal of the secondary winding of the auxiliary transformer shall be connected to the earthing terminal on the transformer tank and as well as to the mast by means of 50 mm x 6 mm MS flat.
Crushed Rock Surface Layer
● At the TSS and switching stations, a surface layer of crushed rock shall be provided to a thickness of about 100 mm. If considered necessary from the point of view of containing the step and touch voltages within the acceptable limits, higher thicknesses may be provided depending on calculation based on site conditions. 14

OHM IMPEDANES
The following values of OHE impedances may be used for the purpose of calculating relay settings: i. Single track OHE without return conductor : 0.4 l ∠70° Ohm/km ii. Double track OHE without RC : 0.24 ∠70° Ohm/km iii. Single track OHE with RC : 0.70 ∠70° Ohm/km iv. Double track OHE with RC : 0.43 ∠70° Ohm/km
Lead Acid Batteries
On electrified sections batteries and battery chargers are installed at the following locations:-
1. Traction Sub-stations -
110V, 200Ah.lead acid cells for control, protection and indication circuits.
2. Switching Stations -
110V, 40Ah lead acid batteries for operation of circuit breakers and interruptors and motor operated isolators.
Specific Gravity
 The specific gravity of the electrolyte should be maintained at about 1.210 at 27° C and when it drops to 1.150 the cell may be considered discharged. These values vary with the type of battery, temperature, age and working conditions.
Cell Voltage
 The voltage of new cells at the end of a full charge will be about 2.5 to 2.75 V when it is receiving charge at the 10 hour rate. This gradually decreases as the age of the battery increases until it comes down to 2.4 V with normal temperature and charging rate. No cell should ever be discharged below the point where the cell voltage reaches 1.85 V as measured when the cell is discharging at the normal 10 hour rate.
Disclaimer: It is clarified that this pamphlet does not supersede any existing provisions laid down by
RDSO, Railway Board or Zonal Railways. The pamphlet is for guidance only and it is not a statutory document.
If you have any suggestion or comment, please write to: Director (Electrical), CAMTECH, Maharajpur, Gwalior (M.P.) – 474 005
Ph.0751-2470740, Fax 0751-2470841 E-mail: [email protected]

(For Official Use Only)
सत्यमेव जयते
Hkkjr ljdkj GOVERNMENT OF INDIA jsy ea=ky; MINISTRY OF RAILWAYS
End User : TrD – PSI Staff
CAMTECH/E/2018-19/PSI Parameter/1.0 June, 2018
egkjktiqj, Xokfy;j & 474 005
Maharajpur, GWALIOR - 474 005

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Hv Double Pole Isolator Traction Power Transformer Type