Burnt neutral conductor

[electro7]

Hi,

I ran into a burnt neutral feeder today. It was burnt at the sub panel it was supplying at the lug/termination point. A few branch circuit grounded/neutral conductors were burnt near the feeder neutral. I could only think that there was a loose connection at that point that caused arcing and eventual burning. Any other suggestions on what could have been the cause?
Thanks

 

[Strombea]

Hi,

I ran into a burnt neutral feeder today. It was burnt at the sub panel it was supplying at the lug/termination point. A few branch circuit grounded/neutral conductors were burnt near the feeder neutral. I could only think that there was a loose connection at that point that caused arcing and eventual burning. Any other suggestions on what could have been the cause?
Thanks

Is there a lot of computers, electronics, fluorescent lighting, dimmer switches, anything DC? Now days more than ever it could be harmonics. Up-size neutral conductors if possible.

 

[templdl]

Hi,

I ran into a burnt neutral feeder today. It was burnt at the sub panel it was supplying at the lug/termination point. A few branch circuit grounded/neutral conductors were burnt near the feeder neutral. I could only think that there was a loose connection at that point that caused arcing and eventual burning. Any other suggestions on what could have been the cause?
Thanks

I think you hit the mail right on the head. When the termination is compromised it will start getting warm. When the load goes away or is reduced it cools. The heating caused expansion then the cooling results in contraction. This continuous cycling will result in the termination becoming looser and looser and with each heating and cooling cycle the termination begins to fail which causes increased heating until the termination often starts to arc.
A failing phase conductor on a breaker as an example can be catstrophic as the arcing can escalated to include a ground and or an ajacent phase. The damage arcing can do is not pretty.

 

[electro7]

Thanks. I was trying to think if there was an overload that had happened but could not think of how that could be on a feeder neutral like that. 240 volt.
It burnt and melted the plastic stand off pretty good.

 

[infinity]

Thanks. I was trying to think if there was an overload that had happened but could not think of how that could be on a feeder neutral like that. 240 volt.
It burnt and melted the plastic stand off pretty good.

If it's 240 volts you can rule out additive harmonic current in the neutral so I would agree most likely a loose connection.

 

[big john]

If the burned up insulation is local to the terminal, then it was high-resistance termination; the further the conductor gets from the heat-source, the better the insulation should look.

If the insulation along the whole length of the conductor is discolored or brittle then it indicates overload. In a uniformly overheated conductor, my experience is they actually get cooler as they approach a good bus termination because it acts as a heat-sink.