Meggering a submergible pump

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teromig

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I have been told at work that we can not megger this 480 volt submergible pump while it is in the water. The water is highly conductive, about like seawater. Is there any reason we can not megger a pump in its working enviroment?

Terry
 
Seems to me it would make the most sense in it's working environment. If the water affects the conductance of the pump motor or conductors, I would think you got problems.

Any reasons given why not?
 
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No was told this Friday from a group supervisor. Will look into Monday, I was just looking for support one way or the other on in the water or out. After I talk to a real electriction at work the whole out look may change. That is why I came here to talk to a real electriction.

Terry
 
No reasons given, will dig into it further tomorrow. Will let you know, I believe it is "just because I told you so".

Thanks,

Terry
 
FIRE THE SUPERVISOR..

If you can not megger the motor in place trash the motor.

Now without sarcasm, Yes you can megger a motor in place it will test the insulation against the harsh environment.
 
When you 'meg' a motor, you are no longer testing for a perfect open circuit, but instead testing the slight leakage current that is always expected from a real insulation system.

It is critical that you not meg at too high a voltage, because doing so can _damage_ the insulation system. Without a proper specification for the test, giving the allowable voltages and leakages, the test is worthless and potentially damaging to the motor.

It seems totally reasonable to me that you be able to test the motor in the water, but it also seems totally reasonable that the test voltages and allowable leakage currents (insulation resistance) would be different for the submerged and the dry motor.

Tom: do you guys have different test specifications when you test motors in the water?

-Jon
 
Winnie:

In the FIELD test are performed to verify/check the condition of the motor in place. Bench testing a new motor is always a good idea, but not practical for regular test to verify how a motor is "DOING" over the course of it usable life. Regular meggering in actual conditions can; if records are kept, be used for predictive maintenance and suggest when it may sensible to rerplace in lieu of awaiting a future fault.

If the company/individual performing the testing has no clue on the proper test voltage and what the results mean, they would be better off subbing this work to a qualified firm/individual. Or test at the excessivly high voltage and then replace the motor.
 
winnie said:
It seems totally reasonable to me that you be able to test the motor in the water, but it also seems totally reasonable that the test voltages and allowable leakage currents (insulation resistance) would be different for the submerged and the dry motor.

-Jon
Click to expand...

Maybe I would be wrong , but I would not expect to see any difference.
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Seems to me you would be reading between windings and from windings to the case.

The motor windings would be in oil and should not have any water in them... If they do, it needs yanked anyway.

Why would you see a difference because of the liquid in which the pump was submerged?
 
Huh.

I just sort of ass-u-me-d that the motors would be flooded with water, rather than oil filled. Dunno why I would think such a crazy thing :)

Actually, a google search for 'wet winding motor' shows that systems where the motor operates flooded with water exist and can be purchased...but I don't think that they are the common approach to submersible motors for water pumps.

-Jon
 
Given the choice to megger a well pump motor in our out of the water, I'd rather do it in the water. More realistic results that way. It is entirely possible that a dry pump motor, out of the water might meg out just barely okay, and when in the water the readings would go to pot. For this reason, I'd rather do the check in the water. It baffles me why the supervisor would want it any other way. This would also be a good check for the submerged cable at the same time the motor is being checked, which otherwise wouldn't happen. Might eliminate a future hazard to personnel that might touch the well head.
 
To all that replied, I will use this information when I talk with them tomorrow afternoon. It should be all taken care of once I get to talk to the technician. You have reconfirmed what I was thinking as to insulation testing on motors.

I have work with and around this field for some 30+ years but not a electrician myself.


Thank you very much,

Terry
 
winnie said:
....systems where the motor operates flooded with water exist and can be purchased....
-Jon
Click to expand...

I never even thought of that, but some circulating pumps such as used in hydronic heating systems are like that. I guess it eliminates the need for a seal, but I don't understand it. Seems exactly like what you oughta be trying to prevent.:smile:
 
winnie said:
Huh.

I just sort of ass-u-me-d that the motors would be flooded with water, rather than oil filled. Dunno why I would think such a crazy thing :)

Actually, a google search for 'wet winding motor' shows that systems where the motor operates flooded with water exist and can be purchased...but I don't think that they are the common approach to submersible motors for water pumps.

-Jon
Click to expand...
I set a few that did operate with the windings immersed in water. Provides cooling without any chance of contaminating the well. I believe they actually came with a water filled casing- warnings not to let it freeze before install.
 
Talked to a real electrician today, (not a supervisor of a mixed group) and was told meggering in the water was not a problem.

Again thanks to all for the help,

Terry
 
Pump has been meggered, passed fine and was left in the water when meggered. All is well again.

Thanks to all,


Terry
 
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