ECN Forum Forums General Topics of the Trade General Discussion Area Ice Storm Surge?

My first guess would be the dropped or intermittant neutral theory. The fact that all of the killed devices were on the same "phase", or leg, kinda wraps it up.

A different primary phase faulting to primary neutral would raise the primary voltage by the voltage drop on the neutral between the fault and the substation source. This could raise the voltage 10% to 30%. The worst case is if that neutral is open, making downstream line-to-neutral connection equivalent to line-to-line for a 73% voltage increase (208 volts, 294 volt peaks for the MOVs). This could certainly damage things, but not generally in ways that look like lightning damage. You would typically see burned up components, but not arc damage. Closer inspection of the damage is what could confirm or deny this kind of problem.

A simultaneous open neutral and phase cross on primary plus an open neutral and phase cross on the secondary could present the very worst case of voltage swell (416 volts, 588 volt peak for the MOVs) assuming the service transformer is not saturated.

If I were inspecting, I'd look for the kind of damage that suggests primary voltage enter the service. Start by pulling the breakers and look at the bus. Primary voltage and direct lightning strikes here could show arc damage.

I would agree. All the upstream primary voltage swell scenarios should affect both service phases the same, unless one of them was faulty.

There is such a thing as coincidence. The problems described may or may not be related to the storm or the primary power lines that were damaged a mile away. You could end up spending a considerable amount of time investigating this and never come up with a real good answer.

Trumpy makes a good point about surge protection. A robust arrestor at the service and some smaller units at the point of use has kept me out of trouble.
If you ever do find the definitive answer to this problem, please post it.

Tom

A good point, Tom.

I remember, back in the 60's, when New York had it's "Great Blackout," one of the newscasters observed that somewhere there was some kid who had stuck a fork in a toaster at the exact moment that everyone lost power ... and, to this day, secretly believes HE'S the reason for the blackout!

Well, I went back to the site today to do a follow-up. I went through the main panel at the meter and checked all connections and looked for any other signs of problem. However, no visible signs and no loose connections. I then went in the house and checked the panel in there again. (This is a rural location that has a pedestal with meter and main then splits off to house and barn.) The phase terminals on the panel in the house were a little loose but not enough that should cause problems. The neutral however was relatively tight. I was able to put a little torque on it but not much.

I then called the PoCo. I explained to them what we were facing. I got the usual, "we haven't had any problems anywhere else." So I asked them to go check their transformer and meter. I haven't heard back yet. I know they are still extremely busy trying to fix the storm damage.

Thanks for all the assistance. I will keep you all updated on anything that arises out of this.

Did you happen to check to see if the primary protector fuses in the outside telephone interface were blown or if the CATV ground block shows any sign of damaged?

Just wondering if maybe the primary power line that broke could have fallen onto the grounded bare messenger for the telephone or CATV overhead lines and caused a momentary high voltage fault between the remaining side of the transformer secondary that was still energized and the grounded neutral and/or main bonding jumper and grounding conductors.
The messenger spans are normally connected to ground at various points along the way, but maybe the initial surge was enough to cause some issues.

That’s my attempt at playing Sherlock Holmes anyway.

I guess this would only be relevent if there were two primary OH lines and a neutral on the pole crossarms.

No, I did not check any tv/telephone connections. The tv and phone were still working fine. Also, there were no overhead telephone lines in this area. All communications are buried in this area. And there is only one primary phase and neutral in the area that was down. However, directly in front of this house there are two primary phases.

It could be a complete coincidence that everything blown was on one phase. Was anything sensitive plugged into the other phase that was not impacted?

Also important, were any surge supressors plugged into the other phase? If a powerstrip on the "good" phase had activated, it would have shunted that surge to ground, protecting not only things plugged into it, but potentially everything else on that phase.

Also worth noting, if a power strip sees a high voltage spike on the ground side, it's electrically identical to a transient on the line side, and it's going to activate.

That is very possible that is what happened, Steve. I don't recall now but that power strip could have been on the other phase. If so, it might have shunted that phase. I don't think anything sensitive was plugged into the other phase. Only thing that I'm not sure about was the computer on that power strip. The strip was smoked but the computer was fine. Thanks for all the input everyone!!