240.21(B) and generators

[Birken Vogt]

permits a CT and over current relay without requiring that combination of devices to be listed

Shh! Don't give them any more ideas.

 

[jim dungar]

The language in 445.13(B) is poorly written. It clearly requires a listed overcurrent protective device, but also permits a CT and over current relay without requiring that combination of devices to be listed. Not sure that the controller would qualify as overcurrent relay.

I don't think you would ever find a listed combination of CT and a relay. There are probably more manufacturers of relays than there are of CTs.

But I can see you point of having the relay listed to provide over current protection equal to a listed OCPD. I know I was often creative in creating Time Current Curves for some generator protection.

 

[don_resqcapt19]

I don't think you would ever find a listed combination of CT and a relay. There are probably more manufacturers of relays than there are of CTs.

But I can see you point of having the relay listed to provide over current protection equal to a listed OCPD. I know I was often creative in creating Time Current Curves for some generator protection.

I was thinking more in terms of the protective relaying used on higher voltage systems.

 

[jim dungar]

I was thinking more in terms of the protective relaying used on higher voltage systems.

I don't think I ever checked for a recognized label, they are usually components in bigger equipment.

Wouldn't the generator overcurrent protection be part of its controller listing?

 

[don_resqcapt19]

I don't think I ever checked for a recognized label, they are usually components in bigger equipment.

Wouldn't the generator overcurrent protection be part of its controller listing?

There is a UL Guide information sheet for the protective relays, "Protective Relays (NRGU)".

No idea if that would be part of the controller listing for a generator..

 

[ron]

Cummins and Kohler have listed controllers that are capable of providing protective relay functionality.

This is the Cummins Amp Sentry

https://www.cummins.com/news/2021/12/03/ampsentrytm-ultimate-protection