Electrical Machines
Minimum allowable resistivity of power transformer insulating oil is generally taken as

  1 X 1012 Ω - cm at 27°C and 0.1 X 1012
 3 X 1012 Ω - cm at 27°C and 0.3 X 1012
 4 X 1012 Ω - cm at 27°C and 0.4 X 1012
 2 X 1012 Ω - cm at 27°C and 0.2 X 1012

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