What are the avantages of using integral earth switch over Earthing truck for HT VCB?

What is IED (related to Electrical engineering)?

Converter transformers

Q1. Primary windings of 2 nos. of double winding Converter transformers are connected to 6.6 KV bus. These transformers are feeding to two nos. of 3 phase , 6 pulse, thyristor converters.
The thyristor converters are controlling 2 nos. of separately excited 600 kW DC motors coupled through shaft .
Now question is what should be the vector group of these transformers and what is the advantage?

Question: What is MMC card which is used in PLC ? How it is different from EPROM and why now a days MMC card is used in place of it.

Question: How safe is to install the oil type Transformer in the basement? Whats the rules says in this regard?