power2020
Electrical
- Aug 18, 2005
- 127
Dear Folks,
We have 11kv substation and then 11/3.3KV step down transformers and 3.3kv substation for 3.3kv motors and then to 400v system through 3.3kv/415v system.
Now My questions..
1) what is the best way to design the 11/3.3kv transformer grounding systems, i mean, either with solid grounding or resistive gorunding? I know most of the MV transformers are designed for resistive grounding. However, i want to know, Is there IEC standard which should says resistive grounding is better for MV transformers (3.3kv or 11kv transformers)?
2) If the transformer,11/3.3kv Dyn11, is with solid grounding what could be the 3.3KV switchgear short circuit rating (withstand time)? we have got the maximum calculated sym sc current is around 10kA, and hence we are going for 25kA switcgear. Now the issue switchgear withstand time rating 1sec or 3 sec.
Is some thing 1 sec is ideal for resistive grounding system? and 3 sec is ideal for solid grounding?
Is there IEC/BS standard which tells about switchgear short circuit current/time rating?
Thanks in advacne for all your valuable suggestions.
Thomos.
We have 11kv substation and then 11/3.3KV step down transformers and 3.3kv substation for 3.3kv motors and then to 400v system through 3.3kv/415v system.
Now My questions..
1) what is the best way to design the 11/3.3kv transformer grounding systems, i mean, either with solid grounding or resistive gorunding? I know most of the MV transformers are designed for resistive grounding. However, i want to know, Is there IEC standard which should says resistive grounding is better for MV transformers (3.3kv or 11kv transformers)?
2) If the transformer,11/3.3kv Dyn11, is with solid grounding what could be the 3.3KV switchgear short circuit rating (withstand time)? we have got the maximum calculated sym sc current is around 10kA, and hence we are going for 25kA switcgear. Now the issue switchgear withstand time rating 1sec or 3 sec.
Is some thing 1 sec is ideal for resistive grounding system? and 3 sec is ideal for solid grounding?
Is there IEC/BS standard which tells about switchgear short circuit current/time rating?
Thanks in advacne for all your valuable suggestions.
Thomos.