Transformer measurement of DC resistance is an important part of transformer test. Through DC resistance measurement, it s possible to check whether the conductive circuit of the transformer is in poor contact, poor welding, coil failure and wiring errors and a series of defects.
HV Hipot GDZRS series three-phase DC resistance tester
The so-called DC resistance of the transformer refers to the DC resistance value of each phase winding of the transformer. The purpose of measuring it is to check whether there is an inter-turn short circuit inside the three-phase winding of the transformer. Because if there is a phase-to-phase short circuit inside the transformer, the short-circuit current will be very large, and it is very likely to burn out the transformer.
However, if there is a short circuit between the turns of one of the phases, the short-circuit current may be very small, and the gas protection of the transformer will trip, but it is difficult to see whether the transformer itself is faulty.
At this time, measure the DC resistance value of each phase of the transformer, and then through the comparison of the three-phase resistance values, it is easy to judge whether there is an inter-turn short circuit inside. If the inter-phase resistance value is very different, the possibility of inter-turn short-circuit fault is very large. If the resistance value of one of the phases is very large or even infinite, it means that the coil of this phase is broken. If the interphase resistances are basically similar, the possibility of a short circuit between turns can be ruled out.
Generally, when the rated capacity of the transformer is unchanged, the greater the DC resistance, the greater the copper loss and the more serious the transformer heating. If the DC resistance is too large, the transformer heats up very much, and the transformer is easily burned out.
Post time: Aug-02-2022