Cooling error in transformer-temperature measurement
Frederick Bauer, Jerome J. Taylor · Electrical Engineering · 1943
In testing transformers, the standard method of determining winding temperature consists of measuring winding resistance at short intervals of time following shutdown, then plotting the readings and projecting them back to the instant of shutdown. The resistances are usually measured by the voltmeter-ammeter or by a bridge. In either method a d-c power source is applied to the circuit, directly or through a resistor.