Confusion on Ground fault protection for equipment.

[Ingenieur]

you have 3 ph ct
a neut ct
and no bonding gnd-neut

perhaps the neut will carry current, ie unbalanced
so to detect a gnd fault they compare the 0 seq to the neut
if 0 seq - neut > 0 must be gnd fault
???

 

[electrofelon]

you have 3 ph ct
a neut ct
and no bonding gnd-neut

perhaps the neut will carry current, ie unbalanced
so to detect a gnd fault they compare the 0 seq to the neut
if 0 seq - neut > 0 must be gnd fault
???

there is a SBJ

 

[Ingenieur]

is the neut ct before or after the tie referenced to the source
would a frame gnd fault bypass the neut ct on its return to the X0?

 

[electrofelon]

is the neut ct before or after the tie referenced to the source
would a frame gnd fault bypass the neut ct on its return to the X0?

The neutral Ct is between the system bonding jumper and the load neutral buss. Thus a L-Gnd fault doesnt go thru the CT on the way back to XO = trip.

 

[Ingenieur]

The neutral Ct is between the system bonding jumper and the load neutral buss. Thus a L-Gnd fault doesnt go thru the CT on the way back to XO = trip.

so if sum(phase i's) + neut i not = 0 must have gnd fault
same as 0 seq - neut > 0 then gf

if you landed gnds on neut then phase + neut + gnd always = 0

 

[electrofelon]

so if sum(phase i's) + neut i not = 0 must have gnd fault
same as 0 seq - neut > 0 then gf

if you landed gnds on neut then phase + neut + gnd always = 0

I concur. I didnt see the neutral CT at first so I couldnt see what difference it would make - not to mention didnt quite get how the GFP would work :dunce:

 

[Ingenieur]

I concur. I didnt see the neutral CT at first so I couldnt see what difference it would make - not to mention didnt quite get how the GFP would work :dunce:

it is not the usual method
typical is on the gnd tie as you said

but this allows current metering, ph relaying, etc
looks like v is measured also
do you have a pic of the relay section/cabinet?

 

[electrofelon]

it is not the usual method
typical is on the gnd tie as you said

but this allows current metering, ph relaying, etc
looks like v is measured also
do you have a pic of the relay section/cabinet?

I'll take one tomorrow.

 

[mivey]

The gear is made by IEM - I had never heard of them. They use GE breakers.

The neutral CT is higher up and toward the front, next to the neutral disconnect link. Hard to see from the back.

Thank you for posting the pics.