Logic Table - 4transformer - Rev2

Rev 2

1 of 10

11kV Incomer & bus coupler CB closing circuit incorporating paralleling logic for 4 transformers

11kV Bus coupler-1 closing circuit

Status of 11kV equipments Status of 33kV eqptsRemarks

I/C-1 I/C-2 I/C-3 I/C-4 B/C-2 B/C-3 B/T B/C-A B/C-B B/C-CO O O NA

O O O NAO O O NAO O O NA

O O O O NAO O C O O NA

O O C O O NAO O O O NAC C O O C I

Tr.1 & 2 ParallelingC C O C O C IC C O O C C C I

C C O O C C C I

C O C C O O C C I

Tr.1 & 3 ParallelingC O C O C C C C I

C O C O C C C C I

C O O C C C O C C C I

Tr.1 & 4 ParallelingC O O C C C C C C I

C O O C C C C C C I

O C C C O O C ITr.2 & 3 Paralleling

O C C O C C C IO C O C C C C C I

Tr.2 & 4 ParallelingO C O C C C C IO C C C O C C C IO O C C C C C I

Tr.3 & 4 ParallelingO O C C C C C I

C C C C O C O C C I

Note1 This scheme gives solution for closing 11kV breaker only, assuming the 33kV is already energised.

2 B/T - both the tie breakers (B/T-1 & B/T-2) shall be enabled to close.

3 C - Close

Close permit

for

Identical Tap Status of breakers

B/C -1 Closing

CB closing without Paralleling of Transformers

Paralleling Tr, 1 &2 when Tr. 3&4 is already

paralleled

Rev 2

1 of 10

O - Open4 I - Indicates that the taps of respective transformers to be paralleled are identical.

Rev 2

2 of 10



Status of 11kV equipments Status of 33kV eqpts



O O O NAO O O NA

O O O O NAC C O O C I

O C C O C C C IO C C O C C C IO O C C C C C I

O C C O C O C I

C C O O C C C I

C C O C O O C I

C O C C O O C C I

C O C O C C C C I

C O O C C C C C C IC O O C C C C C C I

C O C O C O C C IO C O C C C C C

C C C C O O C C C C I



3 C - Close

Close permit

for


B/C -2 Closing

Rev 2

2 of 10


Rev 2

2 of 10

Remarks

Tr.2 & 3 Paralleling






CB closing without Paralleling of

Transoformers

Paralleling Tr, 2 &3 when Tr. 1&4 is already

paralleled

Rev 2

2 of 10

Rev 2

3 of 10



Status of 11kV equipments Status of 33kV eqptsRemarks



O O O O NAO O O O NA

O O O C NAO C C O C C C I

Tr.2 & 3 ParallelingC C O O C O C I

C C O O C I

Tr.3 & 4 ParallelingO O C C C C C I

O O C C C C C I

C C O O C C C ITr.1 & 2 Paralleling

C C O O C C C IC O C O C C C I

Tr.1 & 3 ParallelingC O C O C C C C IC O O C C C C C C I

Tr.1 & 4 ParallelingC O O C C C C C C I

O C O C C C C ITr.2 & 4 Paralleling

O C O C C C C C I

C C C C C O O C C I



3 C - CloseO - Open

4 I - Indicates that the taps of respective transformers to be paralleled are identical.

Close permit

for


B/C -3 Closing

CB closing without Paralleling of Transoformers

Paralleling Tr, 3 &4 when Tr. 1&2 is already paralleled

Rev 2

3 of 10

Rev 2

8 of 10

11kV Incomer & bus copler CB closing circuit incorporating paralleling logic for 4 transformers

11kV Bus Tie-1&2 closing circuit

Status of 11kV equipments Status of 33kV eqpts

I/C-1 I/C-2 I/C-3 I/C-4 B/C-1 B/C-2 B/C-3 B/C-A B/C-B B/C-CO O O NAO O O NAO O O NA

O O O NAO O C O O NA

O O O O C NAC C O O O C C C IC O C O C C C C I

C O C O C C C C I

C C O O C C C IC C O O C C C IO C C O C C C IO C C O C C C IO C C O C C C IC O O C C C C C C IC O O C C C C C C IC O O C C C C C C IO C O C C C C C IO C O C C C C C I

O O C C C C C I

O O C C C C C I

C C C C O C O C c C I



3 C - Close

Close permit

for


TIE Breaker 1

& 2

Rev 2

8 of 10


Rev 2

8 of 10

Remarks








Transoformers

Paralleling Tr, 1 &4 when Tr. 2&3 is already paralleled

Rev 2

8 of 10

Rev 2

4 of 10


11kV Incomer-1 closing circuit

Status of 11kV equipments Status of 33 kV eqpts.I/C-2 I/C-3 I/C-4 B/C-1 B/C-2 B/C-3 B/T B/C-A B/C-B B/C-C

Incomer-1

O O O NAO O NA


C C O O C IC O O C C C C IC O O C C I

C O O O C C C C IO C C C O O C C IO C O C C C C IO O C C C C C C C I

C O O C C C C IO O C C C C C I

C C C C O C O C C C I

C C C O C O C C C C i



3 C - CloseO - Open


Close permit for


Rev 2

4 of 10

Remarks





Transoformers

Parlleing Tfr. 1&2 when Tfr.3&4 is already paralleled


Rev 2

5 of 10




Incomer-2

O O O NAO O NA

O O O O NAO O O O NAC C O O C IC O O C C C C IC O O C C I

C O C O C IO C O C C C C IO C O C C I

O C C C C C IO O C C C C C I

O C O C C O C C I





3 C - CloseO - Open


Close permit for


Rev 2

5 of 10

Remarks





Transoformers

Parlleing Tfr. 1&2 when Tfr.3&4 is already paralleledParlleing Tfr. 2&3 when Tfr.1&4 is already paralleled

Rev 2

6 of 10




Incomer-3

O O O NAO O NA


C O O O C C C C IC O C C O O C C IC O O C C C C I

C O C O C IO C O C C C C IO C O C C I

C O C O C IO O C C C C C I

O O C C C C I




2 B/T - both the tie breakers (B/T-1 & B/T-2) shall be enabled to close.`

3 C - CloseO - Open


Close permit for


Rev 2

6 of 10

Remarks





Transoformers



Rev 2

7 of 10




Incomer-4

O O O NAO O NA

O O O O O NAO O O O NAC O O C C C C C C IC O O C C C C IC O O C C C C I

C O O C C O C C IO C O C C C C I

O C O C C C C IC O C O C I

O O C C C C C IO O C C C I




2 B/T - both the tie breakers (B/T-1 & B/T-2) shall be enabled to close.`

3 C - CloseO - Open


Close permit for


Rev 2

7 of 10

Remarks




CB closing without Paralleling of Transoformers



Rev 2

9 of 10

Tripping circuit- Buscoupler-1, Buscoupler-2, Buscoupler-3 and Tie breaker

Trip ToStatus of 11kV equipments 33kV eqpts.Trip

RemarksI/C-1 I/C-2 I/C-3 I/C-4 B/C-1 B/C-2 B/C-3 B/T B/C-A B/C-B B/C-C

Bus coupler-1

C C C Trip/OpenC C C C Trip/OpenC C C C C Trip/Open

Bus coupler-2

C C C Trip/OpenC C C C Trip/Open

C C C C Trip/OpenC C C C C Trip/Open

Bus coupler-3

C C C Trip/OpenC C C C C Trip/Open

C C C C Trip/Open

Bus Tie

C C C C C Trip/OpenC C C C C Trip/Open

C C C C C Trip/OpenC C C C Trip/OpenC C C C Trip/OpenC C C Trip/OpenC C C Trip/OpenC C C Trip/Open

C C C C Trip/OpenC C C C Trip/Open

Note

1


3 C - CloseO - Open

The above logic is required for tripping the respective 11kV Bus couplers when the upstream (33kV) Bus coupler is opened for a fault or manual command during transformer paralleling.

Rev 2

10 of 10

Transformers on Parallel

On ParallelStatus of 11kV equipments

RemarksI/C-1 I/C-2 I/C-3 I/C-4 B/C-1 B/C-2 B/C-3 B/T

Transformer 1&2C C C

Please refer noteC C C C C

Transformer 2 & 3C C C


Transformer 3 & 4C C C


Transformer 1& 3C C C C

Please refer noteC C C C

Transformer 1& 4C C C


Transformer 2& 4C C C C C

Please refer noteC C C C

Note

1 Following conditions are added in the parlleling of transformers.

2 A Local/Remote switch has been provided to allow initiation of the parallel operation from the Local Transformer Interlocking panel or from the Remote LDC panel.

3 When Local is selected, then the operator has to select the two transformers that are going to be paralleled from the Local selector switch. Let us say the operator selects transformer 1 and 2.

4 When both the signal are got, the initiation for Paralleing Transformer 1 and 2 is provided.

5 Then the breakers which are required for paralleling these transformers are checked whether they are in service.

6 If all the required breakers are in service, then we proceed to the next step.

7 The Transformers 1 and 2 can be paralleled by making I/C-1 or 1/C-2 or B/C-1 or B/C-2 or Bustie as target breakers.

8 When one of the breakers is selected as the target breaker, then that breaker needs to be in the open condition,and the other required breakers are required to be closed condition.

Rev 2

10 of 10

9 When the above is satisfied, signals are provided to set the transformer 1 and 2 in Parallel mode AND then AVR-1 is set in the Master mode and AVR-2 is set in the Follower mode.

10 Now the AVR checks whether both the transformers are in the identical tap. The AVR output is "0" when they are identical and "1" when they are non - identical.

11 When the two transformers are at identical taps, close permissive signal is given to the respective Breaker'S BCU,provided the other condition for closing of the target breaker as required in the other Logic table is also satisfied.

12 The logic given above is used to latch the condition after the target breaker has been closed.

13 The Digital O/P from the Transformer Interlock Panel is not directly wired to the respective AVR for Mode selectionsuch as Master/Follower and Parallel/Independent. This is because, loss of D.C Auxiliary supply to Transformer interlocking panel shall not change the mode of AVR that is already selected. Hence Bistable/Contact multiplicationrelay with Electrical Set/Reset feature is considered.

14 C - CloseO - Open

Logic Table - 4transformer - Rev2

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