Lighting/Surge arrestors in pump drive systems 3

[tedzrt800]

I have a well pump that has a ITT, Aquavar drive pump/motor assembly. It has a line reactor on the lineside of the drive. In the past 3 weeks we have had a couple lighting storms which have taken out the drive twice, (according to the vendor). Presently, we are installing a 3 phase Flowtronex S.L.A.P. arresstor which should eliminate the problem. However, my questions have not been answered by the vendor or the manufacturer, as of yet, are
1. If the arrestor is connected in parallel to the lineside conductors feeding the Aquavar Drive how can it "Drain" of the light/surge charge pass through the ground without effecting the drive circuitry itself?
2. Is there not two directs that the "lightning/Surge" can come from? (Lineside or Loadside)
Please advise,
ZRT800

 

[itsmoked]

1) Most "overvoltage" protection schemes *are* parallel solutions. The intent to conduct the voltage exceeding the "appliance's" ratings elsewhere. The "drive" voltages should not then be "drained off too".

2) Yes but either way the parallel arrestor will do the job. However if the strike current actually runs through anything you care about, it will be toast. The arresting scheme must be layed out to prevent this.

 

[dpc]

I agree with smoked, and will only add that it is crucial that the surge arrestor be located as close as possible to what you are trying protect and that it have a good straight short (and big) path to ground.

I've never heard of "Flowtronex S.L.A.P." arrestor, but be aware that there are a lot of snake oil salespersons in the surge protection market. Any reputable manufacturer's arrestors will work if properly selected and installed.

But any arrestor can fail if the lightning surge is big enough and close enough.

 

[VEBill]

The original question is actually a very good one.

Assuming for the moment that lightning is really what happened...

It would seem to be most likely that the lightning would treat the cable going down the well hole as a single common mode conductor and possibly find something at the bottom end to arc into oblivion (from the bottom of the cable to anything wet).

It doesn't seem reasonable that lightning could generate a significant differential voltage across the down-hole system at the end of a very long cable. Even if it did, the common mode voltage to ground might be much higher.

Given that there are two samples to examine, they should be able to (dis)prove this possible failure mode with a simple inspection and some measurements.

If I'd had this problem, I'd try to give the lightning another path to ground (at the top end) and add some common mode inductance to the well's power cable.

I hope that sort of approach is included in their solution.

YMM certainly V.