86 Relay TX Protection

[Sn00ze]

Silly question:

I have no more NC contacts from an ABB RXMBV4 RK251401 relay to block close 2 more feeder breakers (a deficiency from the project before me).

I've read literature that suggest you can change the contact stacking from NO to NC. But i've no experience doing this. Has anyone heard of this before? Or is basically ordering a new relay the only option available? Also, would you replace the existing 86 relay with one with more NC contacts? or would you connect it in series with the existing one?

I appreciate your responses, thank you.

 

[ScottyUK]

If physical constraints like panel cut-outs favoured it I would replace the relay with one having more contacts. I wouldn't entertain field-modifying a critical relay in my protection scheme, and I would be unhappy if someone else was doing so on the system I'm responsible for: just because it looks OK doesn't mean it performs like a factory part, and it is easy for the inexperienced to damage something without realising it. The relay techs of old who had the skills to strip and rebuild relays are pretty much extinct - try finding someone to overhaul and re-certify induction disc relays these days...

 

[Sn00ze]

@ScottyUK, ah! Good point. Yes, I am leaning towards purchasing a new relay to replace the existing one.

Thank you sir!

 

[JG2828]

You should not attempt to modify the RXMVB relays. You should either replace it with a new one, or add a second one and wire it in parallel with the first one.

http://new.abb.com/substation-autom...relays-and-accessories/auxiliary-relays/rxmvb

 

[Sn00ze]

Thanks JG2828. I agree. I will order one with 11NC and 3 NO contacts and replace the existing one. Thanks for your help