ABTS LOGIC

ABTS logic truth table for two transformer arrangement
Closing Logic











Tripping Logic
















Note:-
ABTS Block
1. Transformer Timed Over current Trip ( This trip non directional some times happend for low side fault also. So its block the ABTS)
2. Lower side BB protection Operated in Unhealthy Bus
3. Over current operate in Lower side Bus Tie
4. FFR operated in Healthy Bus
ABTS Initiation
1. Low side Incomer Manual opens
2. High side instantaneous transformer protection trip
3. Transformer Mechanical protection trip
4. High side BB protection trip
General Conditions
1. All low side breakers should be in service conditions
2. One Bus should be unhealthy condition
3. One Bus should be healthy condition
4. ABTS in service position

INTER LOCK FOR TRANSFORMER HI & LOW SIDE INCOMER

LOW SIDE CB RACK IN BLOCK
1.Low Side Inter locks
1.1 CB Aux Contact - CB should be open Condition
1.2 Bus Earth & feeder line side switch should be Open condition
2 Hi Side Inter Locks
2.1 Transformer side ES should be open condition

LOW SIDE CB CLOSE BLOCK COIL
1. Transformer Protection all lockouts should be normal position
2. 34.5kv Bus earth switch should be open

LOW SIDE CB CLOSEING COIL
1.Hi side breaker should be in close condition
2.Transformer side Disconnector switch should be in closed condition.

LOW SIDE CB TRIPPING

1.All protection LOR

2.High side CB service condition and open

LOW SIDE INCOMER EARTH SWITCH
1.Hi side breaker should be in open condition
2.Transformer side Disconnector switch should be in open condition.

HI SIDE TRANSFORMER FEEDER DS INTERLOCK
1.Low side CB open
2.Low side ES open
HI SIDE TRANSFORMER FEEDER ES INTERLOCK
1. Low side CB open
2. Low side CB in test position

BB PROTECTION TRIP TRANSFER

If any problem in one bus the BB protection relay will trip the CB's in fulty Bus and also Bus coupler and Bus section breakers.

If any problem in opening of Bus coupler or bus section breakers the after 100ms (ABB -REB500) & 250 ms ( Siemens) the relay will transfer the Trip to other buses.

This time delay need for other BF & PD scheme also.

230kV RATED SF6 GAS PRESSURE

Normal condition ( At 20 dec Tem)
CB - 0.630 Mpa
VT - 0.630 Mpa
OTHERS ( ES, DS, GIB ) - 0.550 Mpa
Pressure Alarams in density Detector
Stage -I Gas Leakage Alaram
CB - 0.605 Mpa
VT - 0.605 Mpa
OTHERS ( ES, DS, GIB ) - 0.495 Mpa
Stage -II Gas Leakage Alaram
CB - 0.560Mpa
VT - 0.560 Mpa
OTHERS ( ES, DS, GIB ) - 0.450 Mpa
High pressure Alaram
OTHERS ( ES, DS, GIB ) - 0.620 Mpa

UNDER FREQUENCY TRIP TO BF INITIATION

Under frequency trip will not given to BF initiation . Because the BF relay current setting will be full 1 Amps and during under frequency trip condition there is no changes in normal current. If U/F trip given to BF it will not operate.