In this paper

the influence of poor contact of measurement circuit on dielectric loss is mainly described. Internal structure of transformer bushing is introduced by example and its equivalent electrical diagram is drawn. After eliminating various factors affecting dielectric loss measurement of bushing

through vector analysis of the additional resistance caused by the rusting of potential pin in the transformer bushing

the real reason for dielectric loss exceeding is found. Through comparing the test data before and after the course of bushing’s maintenance

the importance of test circuit contact for accurate measurement of dielectric loss is presented

and finally

some suggestions on maintenance of transformer bushing are made.