Insulation test standard

[voltaire]

Kung mag megger ka ba ng isang motor eh anung reading yung papasa sya? ilang megaohms ba? kung ang voltage nya eg 230vac(motor)?

BR

IR => (1 + 1/KV) Mega Ohm

[tony]

hi,

i am an OFW working as a QA/QC engineer in the Sahkalin Islands, we build oil and gas facilities....

installations consists of big motors rated at 6.6/10kv and power transformers rated at 10MVA/35KV...

cables rated at 10 or 35 kv's are common...

now for testing these cables after they are terminated, we do both meggering, then high-pot, and then meggering after high-pot...these testing are done as per Shell DEP standards...

meggering is for 1 minute at 5kv test voltage.....

for high pot, we use 10kv test voltage for 3 minutes....the goal of this test is to find out if the insulation resistance remains high.......i.e. leakage current is not increasing with time.....

same thing is done with big motors and alternators of medium to high voltage types...

now for low voltage motors less than 30kw, only meggering is done...otherwise, polirization index if performed, the criteria is that the polarization index should be greater than 1.....testing time is about 10 minutes with readings taken every minute...

[squelch]

BM...
boss Piona, can u update the link (Insulation Standard ng IEEE) ?

[tony]

i case polarization index fails, or even meggering fails, what we do is heatup the motor or transformer to get moisture out....then we retest....

i case of cable failure, we redo the terminations and test again....

meggering is not done under rainy conditions where moisture in the air is high....

when i was working in the singapore SOP project, we had to soak the armature at 110volts for 3 days to get the meggering amd leakage current test to pass, it was a 3.3kv motor used for seawater intake....