High leg voltage to ground

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starsandstripes

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On a 3 phase 4 wire delta system I have the expected voltage of 208 from neutral to the high leg. Phase to phase all read 240 volts. A and C phase both read 120 volts to ground. B phase, the high leg reads 130 volts to ground. Does this mean the neutral is not bonded to the ground? if so what are possible problems with this? Thanks for your comments.
 
starsandstripes said:
On a 3 phase 4 wire delta system I have the expected voltage of 208 from neutral to the high leg. Phase to phase all read 240 volts. A and C phase both read 120 volts to ground. B phase, the high leg reads 130 volts to ground. Does this mean the neutral is not bonded to the ground? if so what are possible problems with this? Thanks for your comments.
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What is your voltage Neutral to Ground?

Lacking the bond will result in an ungrounded system.
 
If there was no neutral to ground Bond, your A&C legs probably would not read 120 volts to ground... Did you mean A&C read 120 volts to neutral? If so, then indeed you're missing your bonding jumper.
 
I would be making sure that it's not really a wye with one phase running a little high for whatever reason (perhaps less load on it).

I've seen services that have evidently been converted from one type of three phase to another, without any decent relabeling. If I saw those readings I would be questioning what the voltages are supposed to be.
 
jaggedben said:
I would be making sure that it's not really a wye with one phase running a little high for whatever reason (perhaps less load on it).

I've seen services that have evidently been converted from one type of three phase to another, without any decent relabeling. If I saw those readings I would be questioning what the voltages are supposed to be.
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He said he does have 208 volts on one leg to neutral. There about has to be no main bonding jumper.

Anything connecting from each phase to ground would create a wye network with the EGC being the midpoint, though if balanced would read about 138 volts on all three.
 
The panel the transformer feeds was off, no load readings. Went back today and checked neutral to ground - 60 volts! Found a bad connection on x4 neutral and repaired. Now reading 208 volts high leg to ground. Zero volts ground to neutral. Would that bad connection have prevented a circuit breaker from tripping on a phase to ground fault?
 
starsandstripes said:
The panel the transformer feeds was off, no load readings. Went back today and checked neutral to ground - 60 volts! Found a bad connection on x4 neutral and repaired. Now reading 208 volts high leg to ground. Zero volts ground to neutral. Would that bad connection have prevented a circuit breaker from tripping on a phase to ground fault?
Click to expand...

Good job.

Yes.
 
starsandstripes said:
The panel the transformer feeds was off, no load readings. Went back today and checked neutral to ground - 60 volts! Found a bad connection on x4 neutral and repaired. Now reading 208 volts high leg to ground. Zero volts ground to neutral. Would that bad connection have prevented a circuit breaker from tripping on a phase to ground fault?
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I Echo the above posters sentiment good job finding the problem.

since you had a partial ground, there is no way to tell if a line to ground-fault would have tripped a breaker. as was mentioned above if there was no connection, you would have an ungrounded system... a line to ground-fault simply would have grounded it, and not trip a breaker.
 
starsandstripes said:
Would that bad connection have prevented a circuit breaker from tripping on a phase to ground fault?
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Would it have? No way to know for sure if a ground fault would have pulled enough load to blast through the bad connection.

Could it have? Yes. I just got done troubleshooting a high resistance ground fault the other day.
 
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