Transformers Protection Schemes

Some types of power transformers

•     300 MVA. 3 Winding Power Transformer      
275 KV / 132 KV / 33 KV. (Y.Y.Δ).

•     75 MVA. & 45 MVA. 2 Winding Power Transformer 1
32 KV / 33 KV.

•     30 MVA 2 Winding Power Transformer  
132 KV / 11 KV.

•     20 MVA & 15 MVA 2 Winding Power Transformer  
33 KV / 11 KV.

      Drawing : single Line diagram for
          protection scheme Click Here
 

300 MVA 3 Winding Power Transformer
Protection Scheme.

•     Main (A&B) Protection:

   1. Differential Protection.

   2. Restricted Earth Fault Protection. (both at 275 kv and 132 kv)
   side neutral of the star winding.

•      BackupProtection:

1. C.B Fail to trip.

2. I.D.M.T Non Direction O/C & E/F relay on 300 KV side

3. I.D.M.T Direction O/C & E/F relay on 132 KV side

4. Inter Trip (through pilot cable).

5. Buchhols Trip.

6. Tap Changer Buchhols Trip.

7. Oil Temperature Trip.

8. Winding Temperature Trip.

9. Cable oil pressure Low Trip. (for cable tails )

10. SF6 pressure Low Trip.

75, 45 And 30 MVA- 2 Winding Power Transformer
Protection Scheme.

•     Main (A) Protection:

   1. Differential Protection.

   2. Restricted Earth Fault Protection.
    (At the neutral of the LV. Winding).

•     Backup Protection:

1. Stand-By Earth Fault relay at the neutral of LV. Winding.

2. C.B Fail to trip. (For 132 KV. C.B only)

3. I.D.M.T Non Direction O/C & E/F relay on 132 KV side

4. Inter Trip (through pilot cable).

5. Buchhols Trip.

6. Tap Changer Buchhols Trip.

7. Winding Temperature Trip.

8. Cable oil pressure Low Trip. (For cable tails)

20 & 15 MVA- 33 / 11 KV, 2 Winding Power Transformer
Protection Scheme.

•     Main (A) Protection:

   1.  Differential Protection.

   2.  Restricted Earth Fault Protection.
(At the neutral of the LV. Winding).
 

•     Backup Protection:

1. Stand-By Earth Fault relay at the neutral of LV. Winding.

2. I.D.M.T Non Direction O/C & E/F relay on 33 KV side

3. Inter Trip (through pilot cable).

4. Buchhols Trip.