Incipient Fault Causes

[trchambe]

Hello all,

I am a newer engineer, and have recently been given the job of performing a sectionalizing study for a local utility. As my employer was going over some of the basics with me, he mentioned enabling incipient fault detection on the substation relays. He was actually not certain how they were caused, he was just aware that it was a potential problem.

Can anyone give a bit more information on just what they are, and how they occur? I've done a good deal of research online, but have found little information.

 

[davidbeach]

So is that like detecting faults before they happen?

in·cipi·ent (in sip?? ?nt)

adjective
in the first stage of existence; just beginning to exist or to come to notice: an incipient illness

Generally the relay element picks up as the fault begins to draw more current than the set point, don't know how much more you can do to respond to incipient faults.

 

[rbulsara]

Incipient faults generally occur due to slow failure (degradation over time) of insulation. It is also more common to happen and detectable in oil insulated transformers. Gas pressure relay can sense that too.

Rafiq Bulsara

http://www.srengineersct.com

 

[trchambe]

rbulsara,

You mention it is more detectable in oil insulated transformers. How is it distinguished from other faults?

It was suggested to me that a small opening in the insulation could result in arcing, but that the voltage through the small opening is so small that the arc cannot sustain. As repeated small arcs occur and damage continues, eventually the break in insulation becomes so large the arc can sustain itself, turning into a 'regular' fault.

Does this sound right? The person who told me this wasn't sure of their cause, but this was his best guess.

 

[rbulsara]

Internal faults in oil filled transformers, could produce gases that if remains trapped in the tank (not all of them do) a gas pressure relay could detect it or better yet periodic dissolved gas analysis could reveal something developing in the transformer.

Degradation of insulation of cables, insulators, windings open to atmosphere or air is more difficult to detect. If the relay has the ability to detect arcing fault currents, it could help. I am not personally aware of those.

Yes, what the "person" told you is correct. Cause could be bad insulation, poor installation and maintenance, harsh environmental conditions, accidental damage..the list can go on.

Rafiq Bulsara

http://www.srengineersct.com

 

[waross]

More sensitive than a pressure switch may be a float type gas detector device.
Google "Buchholz relay"

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[trchambe]

Thanks for the suggestions. I may have misunderstood... my boss may well have been referring to Buchholz Relays. I'll have to double check with him.

Thanks again

 

[bacon4life]

One other possibility is high impedance elements for distribution lines. They analyse the waveforms to detecting arcing associated with high resistance ground faults and with intermittent faults.