4160 volt motor insulation test

[a.bisnath]

For all my working life I have meggered 4160 volt motors at 5000 volts,recently I have been hearing this is wrong,is there any proof of this?Will this damage the winding?

 

[kwired]

For all my working life I have meggered 4160 volt motors at 5000 volts,recently I have been hearing this is wrong,is there any proof of this?Will this damage the winding?

Can't speak for medium voltage stuff so much but for low voltage I thought they recommend testing at about twice the normal operating voltage.
So for 240 volt motors I test with 500 volts and 480 volt motors are tested at 1000 volts.

 

[eric9822]

Biddles A Stitch In Time is an excellent resource for insulation testing. Test voltage levels are discussed on page 16. I have always tested 4160V motors at 5000V because that was the highest setting on our tester. Our new tester will go to 10KV but that is a little too high according to Biddle.

 

[Jraef]

Biddles A Stitch In Time is an excellent resource for insulation testing. Test voltage levels are discussed on page 16. I have always tested 4160V motors at 5000V because that was the highest setting on our tester. Our new tester will go to 10KV but that is a little too high according to Biddle.

I'm no expert on MV motor testing, but NETA ATS-2007 Section 7.15.1 for motors and MTS-1997 Table 10.1 for gear says that 5kV rated equipment should be tested at 2500VDC. They don't show using 5000VDC until the equipment rating is 25kV.

 

[eric9822]

I'm no expert on MV motor testing, but NETA ATS-2007 Section 7.15.1 for motors and MTS-1997 Table 10.1 for gear says that 5kV rated equipment should be tested at 2500VDC. They don't show using 5000VDC until the equipment rating is 25kV.

Thanks for the insight. I must admit I haven't looked into this in detail in a really long time. ATS-2009 Section Section 7.15.1 points to ANSI/IEEE Standard 95. IEEE 95-2002 section 2.2 says this:

In general, an alternating voltage test ranging from125 to 150 percent of the rated rms line-to-line voltage (E) has proven adequate. This is approximately equalto 65 to 75 percent of 2E + 1000 V, depending on the voltage rating of the equipment to be tested. The direct voltagetest value for maintenance tests is 1.7 times the alternating voltage (rms) maintenance test value (50Hz or 60 Hz)

Following IEEE 95 would come up with a test voltage of around 9KV.

I don't have access to MTS-1997. I looked at a manual I have for GE Custom 8000 4160V motors and it suggests 500-1000 volts but also refers the user to IEEE 43. I ran across some other white papers that seem to suggest 2500V as the proper test voltage. I was sure 5000V was correct but now not so much.

 

[AZElectrical]

IEEE 43-2013 Table 1 provides recommended test voltages based on the L-L voltage rating of the machine. A 4160V motor should be tested between 1000-2500VDC, per the standard.

 

[zog]

I'm no expert on MV motor testing, but NETA ATS-2007 Section 7.15.1 for motors and MTS-1997 Table 10.1 for gear says that 5kV rated equipment should be tested at 2500VDC. They don't show using 5000VDC until the equipment rating is 25kV.

That table does not apply to rotating equipment

 

[Tony S]

From previous experience and UK rules

Ph to Ph 2x Voltage IE 10KV
Ph to ground 2x voltage IE 6KV

The maximum permitted leakage current is 1/10,000^th of FLC

The minimum acceptable insulation is calculated by ohms law.

The readings may appear low but they are minimum, that doesn’t mean I’ve not given a motor a try at below minimum.