Lost A Phase

Toolwh@#e

Lost a phase on the 600 volt service in my brother in law's shop. Turns out a fuse was blown. Replaced it and it blew again even though I isolated everything outside the splitter box. Called in my electrician and he can't figure it out. Three electricians and me stood there not being able to figure out whats wrong. All the safety switches coming off the splitter are shut off and there is no problems coming from the safety switch to the splitter and no problems in the splitter it self. Has anybody heard of anything like this?

Leo G

Did you check to see that the fuseholder hasn't somehow grounded out on the box?

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mrmike

First of all, 3 Electricians should have been able to figure this out. There is obvious leakage to ground & I would check the fuseholder first as Leo said. Then I would check the "in" lines on the safety switches. If they aren't Knife type switches there could also be a fault with them-- There is some kind of grounding there someplace !

woodchuck2

X3, i agree with the short to ground. Where is easy enough to verify with a meter. Time to tear into it IMO.

Celtic

Haphazardly replacing a fuse w/o identifying the actual the actual problem is a sure way to maintain the failure ~ or worse.

Find the source of the short and/over current and remedy the situation before blowing up any more fuses ~ or worse.

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Cow

Has anyone tried using a Megger? I bet you'd find the problem in no time at all...

mrmike

Usually in a case like this one you only need your ohmeter to find the problem. I personally have used a meggar hundreds of times on high voltage cables & equiptment. The meggar isn't going to pinpoint the problem any quicker than an ohmeter. You still have to "dig" into it to find out what the short actually is. The meters are just a tool to help you do that........................

Railman

Considering it's 600 volts, couldn't you have a condition where you wouldn't get a reading with an ohmeter, but could arc under voltage? It's a common occurance with car ignition coils. At 600v the insulation value only needs to be reduced, so as to allow arcing. I'd start by breaking down the box's. If no arc damage is visable, it has to be in the conduit feed to the safety disconnect. It seems like there would be some burnt odor involved at some point.
Joe

mrmike

Yes, you are correct, by meggaring it & putting the 600v's to it, would show the voltage breaking down & going to ground, but as I said usually will not pinpoint the cause.. We always started with an ohmeter & looked for visual stuff as you stated. If you still couldn't find the problem you could bring out the Meggar and check Point to point, which was pretty rare for us. We never started the troubleshooting process by starting with a meggar