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Question
how to calculate the megger values for motor, cables and 
transformers?
 Question Submitted By :: Sundar C
I also faced this Question!!     Rank Answer Posted By  
 
  Re: how to calculate the megger values for motor, cables and transformers?
Answer
# 1
The thump rule is voltage rating +1 example for a 11KV 
motor it should be 11+1=12 Mega ohm.
In addition to that the PI is the ratio between 1Mnts and 
10 mnts.It should be above 1.5
For examle IR at 1mnts= 10M.ohm,
IR at 10 Mnts= 20 M.Ohm
Then the Polarisation index is 2 which is consdierd 
good.When it is below 1.5 you can heat the tranformer or 
motor then the value will come up.
 
Is This Answer Correct ?    4 Yes 0 No
Karan
 
  Re: how to calculate the megger values for motor, cables and transformers?
Answer
# 2
see sundar
Meggering test is done for any electrical equipments to 
find the insulation resistance value.
As per the standards for testing the machines 3 methods are 
there
1)spot reading 2)time-resistance testing method 3)step 
voltage test
the following is the second mehtod it is  in use nowadays
PI=10 min/1 min value
Then the Polarisation index is 2 which is consdierd 
good.When it is below 1.5 you can heat the tranformer or 
motor then the value will come up.
 
Is This Answer Correct ?    2 Yes 0 No
Priyan
 
 
 

 
 
 
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