DISTRIBUTION TRASFORMERS PROTECTION

DISTRIBUTION TRASFORMERS PROTECTION-There are basically following rating  transformer comes under  distribution.

10kva, 63kva, 100kva,160kva, 250kva, 400kva, 630kva, 1000 kva.

 For all larger rated and important distribution transformers, over current protection along with restricted earth fault protection is applied. Differential protection should be provided in the transformers rated above 5 MVA(power transformer).

For distribution transformer in most of the times fuse system is used.

And copper strands are used in fuse. It’s cross section vary according to rating of transformers.

Step to follow save distribution transformer (D T) are as follow-

1-    Natural of  DT should be earthed  properly with low resistance wire.

2-    L T’s circuit should not be  short circuited (means phase to phase short circuiting)

3-    Oil level should be upto L T bushing

4-    Fuse at L T side and H T side be as per rating of transformer

5-    Current ( load)  should be not beyond  80% of  its rating.

Nature of Transformer Faults

Although an electrical power transformer is a static device, but internal stresses arising from abnormal system conditions, must be taken into consideration. A transformer generally suffers from following types of transformer fault-

1.     Over current due to overloads and external short circuits,

2.     Terminal faults

3.     Winding faults

4.     Incipient faults

All the above mentioned transformer faults cause mechanical and thermal stresses inside the transformer winding and its connecting terminals. Thermal stresses lead to overheating which ultimately affect the insulation system of transformer. Deterioration of insulation leads to winding faults. Some time failure of transformer cooling system, leads to overheating of transformer. So the transformer protection schemes are very much required. The short circuit current of an electrical transformer is normally limited by its reactance and for low reactance, the value of short circuit current may be excessively high.-There are basically following rating  transformer comes under  distribution.

10kva, 63kva, 100kva,160kva, 250kva, 400kva, 630kva, 1000 kva.

 For all larger rated and important distribution transformers, over current protection 

along with restricted earth fault protection is applied. Differential protection should be 

provided in the transformers rated above 5 MVA(power transformer).

For distribution transformer in most of the times fuse system is used.

And copper strands are used in fuse. It’s cross section vary according to rating of 

transformers.

Step to follow save distribution transformer (D T) are as follow-

1-    

Natural of  DT should be earthed  properly with low resistance wire.

2-    

L T’s circuit should not be  short circuited (means phase to phase short circuiting)

3-    Oil level should be upto L T bushing

4-    Fuse at L T side and H T side be as per rating of transformer

5-    Current ( load)  should be not beyond  80% of  its rating.

Nature of Transformer Faults

Although an electrical power transformer is a static device, but internal stresses arising from abnormal system conditions, must be taken into consideration. A transformer generally suffers from following types of transformer fault-

1.     Over current due to overloads and external short circuits,

2.     Terminal faults

3.     Winding faults

4.     Incipient faults

All the above mentioned transformer faults cause mechanical and thermal stresses inside the transformer winding and its connecting terminals. Thermal stresses lead to overheating which ultimately affect the insulation system of transformer. Deterioration of insulation leads to winding faults. Some time failure of transformer cooling system, leads to overheating of transformer. So the transformer protection schemes are very much required. The short circuit current of an electrical transformer is normally limited by its reactance and for low reactance, the value of short circuit current may be excessively high.