Change Settings on Protective Relays

[hidalgoe]

Hello:

I work for a US government agency.

We recently replaced our 30 year old substations in our administrative building.

Quite recently a grounded\shared neutral situation caused a feeder ground fault relay to trip the feeder breaker.

To remedy the situation we will have to revise the ground fault relay setting upwards.

A signed and sealed short circuit/protective device coordination study was done by a licensed electrical engineer. The settings our protective devices have are those that his PE recommended in his study.

My question is: do we have to call him and report what out intent is regarding the ground fault relay? Is it ethically required/recommended?


Please help.

Eugene Hidalgo, PE

 

[MiketheEngineer]

You own it and can change it any way you want - with all the responsibility that goes with that. MY FAVORITE SAYING - YOU CHANGE IT - YOU NOW OWN IT - Don't call me if it doesn't work. I am not an EE - but CE and have this type of problem all the time.

BTW - I would call him to find out why it didn't work correctly the first time.

 

[IRstuff]

Did they do this work without offering a warranty?

TTFN
faq731-376

 

[dik]

Can the modification be life safety related? If so, then hands off and get the original consultant on board or a new one.

Dik

 

[MintJulep]

To remedy the situation we will have to revise the ground fault relay setting upwards.

It may remedy the situation, but does it solve the problem that caused the situation?

 

[mayanees]

You've raised a couple points that warrant discussion. First and formeost, if you found a neutral/ground problem, then the Study's settings may have been appropriate, and not warrant changing. And as an earleir post states, one you change it, you own it.
But gf settings can be subjective. Many engineers attempt to set the main gf pickup more sensitive than what the NEC allows, and I'm not one of them. I set for the allowable max on low voltage systems, 1200 amps for 1 second, and let the downstream devices have a chance to operate. If it's medium voltage, then set for coordination with the upstream ground fault device. And if it's off a separately derived system, set for 20-30 % of the phase pickup.
I suggest that as a PE, you provide settings within allowable limits.
John M