Abstract: The dielectric loss test of the end screen is of great significance for the detection of moisture defects in capacitive current transformers. The regulations stipulate that when the insulation resistance of the end screen of the current transformer cannot meet the requirements (less than 1 000 MΩ), the dielectric loss of the end screen to the ground should be measured to further judge its insulation status. In this paper, from the aspect of structure and dielectric loss test principle of capacitive current transformer, with the help of equivalent circuit, combined with actual test cases, the dielectric loss of current transformer is analyzed when the primary winding is suspended, the primary winding is grounded, and the primary winding is short-circuited and connected to the high-voltage shield. The dielectric loss measurement of the end shield in the three methods shows that the measurement results in the method of short-circuiting the primary winding to the high-voltage shielding method are the most accurate.

Key words: capacitive current transformer;end screen, dielectric loss, shielding