Protection Relay: SEL351 fault flags

[warickwrx]

Hi

Has anyone experienced incorrect flagging on the front of these relays for single phase earth faults, it shows/flags more than one phase for a pure earth fault trip/operation

thanks

 

[cranky108]

Have you looked at the event report? You might want to be sure the fault was what you thought it was.

Often faults can transision from what they start out as, into something else. Or you could have a large negitive sequence flow that fools the relay.

 

[warickwrx]

Yes I have considered this, but it behaves in this manner when I am injecting the relay with a test set.

 

[DTR2011]

I would inspect the logic, you may also need to set the device to "TAR 0", as the LED's follow the target command.

 

[dpc]

I have not seen this. The SEL-351 has been around for awhile, so unless this is an old relay that has never had a firmware upgrade, I think if there was an actual problem with the targets, it would have been addressed already. Of course I've been wrong before.

I agree with checking the logic. Just because the relay has label next to the LED doesn't mean it is programmed to match. Also, if you're having issues, I would not hesitate to contact SEL support. They are generally pretty helpful.

 

[DTR2011]

Additionally, how are you injecting the fault? If, for example you are injecting A-N, I would expect an A & N or G Target. IIRC, the "TRip" Equation sets the default targets. There may be additional logic added to this equation. The SEL platform is very flexible and with that comes a bit of complexity (if you are not familiar with it).

 

[dpc]

You could also have a look at the Event Report.

 

[mgtrp]

I don't believe that the SEL-351A has programmable front panel targets, in which case I would suspect either incorrect test method (most likely), something very strange elsewhere in the logic (not likely), or an actual issue with the relay (very unlikely).

I second contact SEL support, my experience with them has generally been excellent.

Regards,
mgtrp

 

[marks1080]

Because SEL does a lot of math inside the box I've found it always best to do three-phase testing. Start with a normal three phase pre-fault set up and then move to whatever post fault state you desire. Injecting single phase quantities can often give you unexpected results.