submersible water well surge protection 1

[agmarine77493]

We are having problems with submersible water well pumps (with motors) failing due to a surge. Our latest design is having surge protection at the service entrance and at the power cable junction box located at the top of the water well head. Both surge protection devices go to ground via a 20' copper ground rod...and these are bonded together via #4/0 bare copper wire. We still are having surges though. I have read that a ground rod does not provide good grounding for the surge protection at the well head...something about ground the aboveground surge components to the motor frame or to the well casing that goes below the well pumping level. Oh yeah, the submersible is approx. 700' below grade. Any ideas or suggestions on better implementation for this application?

 

[dpc]

Some basic oversimplification:

1. Most important is that the surge protection be as close to the equipment you are trying to protect as possible.

2. Grounding connections from the surge arrester to ground should be as short as possible with as few bends as possible with a large copper conductor.

3. Resistance to earth should be as low as possible.

Usually for a submersible, the best approach is a direct bonding from the surge arrester to the metal well casing. You could also add a buried ground ring with multiple ground rods around the wellhead.

 

[agmarine77493]

Thanks DPC for the reply.

When you say "Usually, for a submersible..." What size (in HP) are you talking about? The submersibles that I am writing about are in the 100 HP to 350 HP range.

Thanks again.

 

[dpc]

Those are large submersibles, but the principles are the same. Sometimes connection to the well casing is not an option, but if you can do it, it should help quite a bit.

Keeping the ground connection short and straight is often overlooked, but it is very important in providing a low impedance path.

Some submersibles are fitted with built-in surge suppression - that is a good option when available.

Are these running constant speed or on VFDs?

 

[jraef]

And what are you using as "surge protection"? Some of the stuff sold out there is junk, basically just a series of small MOVs that pop the first time they see a hit. They work, but only once!

 

[agmarine77493]

At the service entrance I will use a Phoenix Contact SystemTRAB no. 5602746 which has the arrestors and TVSS...and at the well head I planned on using another Phoenix Contact SystemTRAB no. 5602746 (again with arrestors and TVSS).

Usually we connect the surge protection devices to ground rods via bare copper wire (#4/0), but after some reading I am considering tying all the rebar together within the concrete base and footings for the well head and bond that to the ground bar(s).

Any thoughts or concerns would be greatly appreciated.

 

[thewellguy]

What voltage are you using? How long are the surges lasting and how did you find them?

 

[agmarine77493]

277/480V, 3-phase, 4-wire service...the MCC bus does not carry the neutral thru...I don't know how long they last...we found them because the motor failed...the windings of the stator were blown out on one of the radial ends.

 

[dpc]

Those sound a little lightweight for outdoor service.

You might look at GE Tranquell Secondary Arresters.

You should put a heavy duty arrester at the service entrance and make sure you are protected between each phase to ground as well as neutral to ground. Then put another arrester at each wellhead.

 

[thewellguy]

I have a couple thoughts. True surge protection that operates in the nano second range is expnsive. I am currently in the middle on this the one of my customers. The motor manufactuer is recommending "IT PROTECTOR" for over/under voltage surges. This is on a 2300 volt system.
I would look at the cost/benefit of the protection.

Before you spend all the time and money on surge protect, I would spend some time reviewing your current motor protect. I frequently talk to customers that are upset taht their motor protect didn't prevent a failure. I then look over their motor protect and they have heaters.

 

[itsmoked]

"Heaters.. Why did it have to be heaters... I hate heaters.." Isn't that what Indiana Jones said?

Are you worried about lightning? What exactly are these "surges"?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[agmarine77493]

We typically use a GE Multilin located at the MCC for motor protection along with surge protection at the well AND the traditional heaters at the starter. The thing about the Multilin is that it is a great product for conditions such as overvoltage, undervoltage, current unbalance, overfrequency, etc...but it isn't fast enough to see surges or protect the motor from them.

These "surges" come either from a lightning strike near the well or a power surge from the local utility. As of yet, we still have not been able to completely tell exactly from where one has come.

 

[thewellguy]

Heaters, I hate heaters.

Ok seriously, I am not familier GE Multilin so no comment about it. I'm a big fan of the Syc-com produce line.

If I understand your statement, the GE product is protecting the whole MCC, you need better protection at the starter.

One other thought, What is the class rating on the GE? Submersible motors are a different breed. All manufacturer's that I know of require class 10 overloads. This is something that regularly gets overlooked. ( I have asked this of many electricions and they look at me like I'm crazy) Submersible motors for warranty requirment are only allowed to run at +/- 10% for voltage and 5% for current imbalance.

Finally, is it a drain back system and if so does it have a back spin time (on delay) ?