Analysis of Abnormal Dielectric Loss and Capacitor of Transformer Winding

Problems encountered during the measurement of transformer dielectric loss between windings or between winding and iron core,such as negative or too big,or too small value of dielectric loss or serous small value of capacitance,are analyzed. It is founded that all abnormal transformers have only iron core grounding but don't have clamp grounding. It is because iron core earth screen was grounded through clamp in transformer that leads to abnormal results. It is suggested that dielectric loss should be remeasured by routine method when such kind of problems are encountered in preventive test.