Transformer separated from MV SWGR at different room 1

[ciy]

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.

 

[jghrist]

I assume you mean that the transformer is downstream from the MV switchgear.

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.

 

[musaUKPN]

If the cable connecting the transformer to MV gear is not very long, I would add no extra breaker. The protection at HV gear and the downstream LV arrangement also to be considered.
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

 

[ciy]

Thanks for your valuable reply.

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.

 

[dpc]

In the US, the 2011 National Electrical Code (NEC) now requires a disconnecting means for each transformer. This is new requirement in the 2011 NEC. The disconnect must be either be within sight of the transformer or lockable if remote from the transformer. If a remote disconnect is used, the location of the disconnect must be marked at the transformer.

The NEC defines "within sight of" as not more than 50 feet (15 meters) away.

David Castor

http://www.cvoes.com

 

[ciy]

dpc, thanks for your useful information!