- #1
F.ono
- 16
- 0
I recently started working at ABB as a engineer. I wish someone here could help with some questions:
1) In a single phase IT system, why does the circuit breakers have to be bipolar? I believe it is because of a second fault occurence, but i don't really understand what happens.
2) If you connect a switchgear to the same earthing system as the transformer neutral is connected, instead of having a cable to directly perform this connection, does it makes your system a TT system? Or the fact that the switchgear is in the same earthing system as the source neutral makes it a TN system?
3) In a three phase system whose neutral is grounded through a resistor, why is it not recommended the existence of single phase loads?
4) Is it necessary to place a CB before and after a potential transformer to guarantee its protection? Does these CB need to have any special features?
If anyone knows any articles or papers about these subjects I'd appreciate!
1) In a single phase IT system, why does the circuit breakers have to be bipolar? I believe it is because of a second fault occurence, but i don't really understand what happens.
2) If you connect a switchgear to the same earthing system as the transformer neutral is connected, instead of having a cable to directly perform this connection, does it makes your system a TT system? Or the fact that the switchgear is in the same earthing system as the source neutral makes it a TN system?
3) In a three phase system whose neutral is grounded through a resistor, why is it not recommended the existence of single phase loads?
4) Is it necessary to place a CB before and after a potential transformer to guarantee its protection? Does these CB need to have any special features?
If anyone knows any articles or papers about these subjects I'd appreciate!