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Reply To: Transformer Riddle No.38 -Transformer megger test

#2097
R K Mohapatra

    The Insulation Resistance is a necesary not sufficient requirement for power transformer – New or Old .Even though there is no binding values as per standards – a value of 2 Mega ohm per kv at 60 C is supposed to be the requirement .However the values should not be less than 1000 mega ohm at room temperature for poweer trnasformers of 132 kV and above . P I value should range from 1.3 to 1.5 under all circumstances . A reduction of P I value is an indication of contamination by moisture or other suspended particles , which must be removed before charging .