What is the effect of back charging of 250MVA 15.75KV 240KV generator transformer and how many times one can back charge the generator transformer?

Answer 1

Generator Transformer back-charging is done because of the following reasons:-

1. To ensure the healthiness of Generator transformer after performing all the transformer related tests before synchronising with the grid.

2. To ensure all the protections of transformer before putting it into actual operation.

3. To check the polarity, ratio & connections of transformer.

4. To check all the PTs & CTs in circuit & their availability to the relays for protection & metering.

5. To check Voltage level & polarity at LAPT.

6. To perform change-over operation checks of UATs & the tie breakers with main breakers.

Since all the protection system related to relays acts in the same way for forward & reverse power, we check the availabilty of each equipment before final synchronisation with the grid.