Surge Arrester

[sonic02]

Hi All,

We are planning of installing three(3)- single-phase,25kVA, 13.8kV/600V, pri- Delta and sec- wye-grounded pole-mounted transformer for our system. For protection on the primary-side of the transformer, I was wondering if I should spec out a self-protected transformer in which the surge arrester comes as an integral part of the transformer or to have both the transformer and distribution class surge arrester as two seperate entities.

I'm sure there are pros and cons with each design but I would like to go with the standard recommendations of NEC or CEC.

Comments and thoughts, pls

Regards,

Sonic

 

[dpc]

Nothing in NEC is going to address this decision.

My suggestion is to use a standard transformer and mount a standard arrester as close as possible. The self-protected transformer will be much more difficult to replace in the future if one should fail.



David Castor

http://www.cvoes.com

 

[jghrist]

Most CSP transformers are single-bushing and not appropriate for delta connection. The utilities that I'm familiar with use conventional transformers for 3Ø banks.

 

[odlanor]

I have seen some utility specify transformer -230/69kV Pri-wye-grounded and sec-delta, including surge arrester to be installed on top of the tank, connected to 230kV bushings.

 

[ssantoshr]

If the surge arrestor is built into the transformer, it is required to determine if additional surge protection is needed on the secondary.
This will depend on the size and importance of the transformer and also the cost and type of arrester. You seems to be using distribution class arrester (inexpensive) which has a very low lightning impulse value compared to station (expensive) and intermediate class arresters.

I would agree with what dpc suggested....the surge arrester should be mounted as close as possible to the transformer terminals, preferably within 1 meter and on the load side of the incoming switch.

However, NEC talks only the briefs of surge arrester under article 280 but does not talk about application on transformers.

Regards
Santosh

 

[sonic02]

Thank you all for the comments.