The transformer shall be under oil without excitation for at least 3 hours.
The measurement shall be performed between the terminals of HV winding, at every tap position, LV and TV (if any) windings by Voltmeter-Ammeter method. Direct current shall be used for the measurement. The temperature of the windings, measured by Thermocouple Type T, shall be recorded. The cold winding resistance shall be corrected to a temperature of 75 ºC. The following terminals shall be measured.