Protection for lost neutral (help)

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K8MHZ

K8MHZ

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Michigan. It's a beautiful peninsula, I've looked
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Electrician
ramironchis said:
I was wondering if a over voltage breaker will work in this case.
Thanks in advance
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If it's a 120 volt breaker, it will only open the circuits on one side, leaving the low voltage side connected. A 240 volt breaker will see the voltage from one leg to the other which will not change with or without a neutral.

Also, if your 120/240 system is fairly balanced and grounded well, the loss of a neutral may not be able to be detected by any type of voltage detection system.
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
GoldDigger said:
Until something happens to unbalance the load, at which point it may be too late. :)


Tapatalk...
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I was on a job where a pole got hit and pulled over a mast. It had been that way for a couple months waiting for insurance type stuff. When we got there to fix it, I noticed the neighbor's house, also serviced by the pole, had it's neutral / messenger cable lying on the roof, disconnected. The triplex was holding the run up.

The area had old, metal water pipe so the neighbor was 'connected' to his neighbor's ground to neutral connection and never noticed any electrical issues.
 
A

arion

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Location
sapporo Hokkaido Japan
just some ideas

just some ideas

read
iceworm said:
Perhaps
It would take two - one for each side of the 120VAC. The alarm contacts go open circuit, so one would have to make up a circuit (interposing relay and power source) to shunt trip a CB and get a shunt trip CB.

The thresholds are pre-set, however one of the settings is 10% (plus or minus) so that is pretty good.

A shunt trip QO 2pole 100A lists for $400. Add $550 for the monitors. Add additional $xx for the control relay/power source.

what is needed here is a ground ring monitor and current probe assuming the ecg and grounding rod are properly in place, the net currenton the grounding jumper will rise at the instant the neutral. opens as the ecg and system neutral bus are interconected at the mains you need to monitor both the ground bus where it ties to the earting electrodes and the system neutral where the utility ties to the system bus. when it is properly operating a groung fault will show up on both bus bars. normal state is 0 amps on the groundbus and line unbalanceamps on the neutral bus. when the neutral fails that amps will try to use the system ground but it will be a hi resisttance path in comparison to the system neutral. both lines willnow be in series across the loads the standard norms for residential service are. L-N min 114V

ice
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