Transformer separated from MV SWGR at different room
Transformer separated from MV SWGR at different room
(OP)
Hi,
I have a question need some advice.
There is a MV/LV transformer upstream from MV SWGR.
However, the transformer and MV SWGR located at different room.
My question is :
Take care the safety and cost reason.
Do I need to prepare another MV breaker at primary side of transformer to connect?
Or just connect to transformer from MV SWGR, no another breaker is needed?
Have any standard or criteria described this?
Thanks for your advice in advance.
I have a question need some advice.
There is a MV/LV transformer upstream from MV SWGR.
However, the transformer and MV SWGR located at different room.
My question is :
Take care the safety and cost reason.
Do I need to prepare another MV breaker at primary side of transformer to connect?
Or just connect to transformer from MV SWGR, no another breaker is needed?
Have any standard or criteria described this?
Thanks for your advice in advance.






RE: Transformer separated from MV SWGR at different room
Generally, I would not think a separate breaker at the transformer would be needed. Is there any need to trip separately for a fault in the cable vs for a fault in the transformer? One possible reason might be to have differential protection for the transformer if the distance between the transformer and the switchgear is too great for the CT leads without having too much burden on the CTs.
If there is anything else served by the cable from the switchgear, then there would be a reason to have separate protection.
RE: Transformer separated from MV SWGR at different room
I have seen many 11/0.4kV transformers connected directly to the short cables. Usually transformer rooms are adjacent to the switchgear room.
musa UKPN
RE: Transformer separated from MV SWGR at different room
In practice for safety reason, additional breaker or DS often is installed before transformer if cable connecting to transformer is long distance relatively.
This purpose may be for isolating safely during maintenance.
However, shorter distance usually no added.
I wonder how many meters need to add extra breaker that specify in code or standard, if any.
May be 20 meters or else that can follow accordingly, or just by experience.
Please advise where I can find the specified,if any.
Thanks again.
RE: Transformer separated from MV SWGR at different room
The NEC defines "within sight of" as not more than 50 feet (15 meters) away.
David Castor
www.cvoes.com
RE: Transformer separated from MV SWGR at different room
dpc, thanks for your useful information!