brian john

These pictures are of two separate ground Fault Protection systems (GFP). The Zero Sequence Current Transformer (CT) work on the basis that there should be no current flowing in the secondary as the 3-phase current and neutral current in the primary (power conductors) cancel resulting in no current in the secondary.

The problem here is the neutral conductors for the two GFP systems are not routed through the CT's, thus the GFP relay sees the neutral current as ground current, this can lead to nuisance tripping. In this instance the neutral current was low due to balanced loads in the distribution panels. But is still an NEC violation that needs to be corrected.

Oh then there is the excessive DUST.

The 4/0 AWG locomotive cable in the picture is out test lead, we were performing a GFP test, we wrap the conductor through the CT twice to minimize the current required to trip the relay. This minimizes stresses on our test set and overcomes the voltage drop in the test leads.

frenchelectrican

Brian:

I have a quick question to ask you on the photo but if my eyes were teasing me on the phase conductors that ran thru the CT doughnut is that 9 cables ?? because i only can see 6 unless 3 are hided from the photo?

BTW that was pretty good trick to deal to test the CT on GFI system there

thank again


Merci , Marc

brian john

I see what you are saying, but there are 3 sets terminated..Need to recount when I get back on site. We are providing a proposal to perform Electrical Preventative Maintenance (EPM) on this gear, and repair the GFP properly installing the phase and neutral conductors.

JohnJ0906

Brian, you post some neat pictures! Thanks!

Just wish I had the experience to understand them a little better

__________________
John from Baltimore
"One day at a Time"
All responses based on the '08 NEC
It's not my fault, it's not my problem, I'm not your solution.

MDShunk

It tickles me to see those old, white zip ties holding the conductors in place. The white ties get so brittle so easily. I know you could probably just flick those with your fingernail and they'd pop right off. I like the black one's (UV rated one's), as they don't get brittle. Rope sometimes too.