Method for testing capacitance and dielectric loss value of 220KV coupling capacitor

The invention relates to a method for testing capacitance and a dielectric loss value of a 220KV coupling capacitor. The method comprises the following steps of: grounding a 220kV circuit which is connected with equipment body through a grounding knife; connecting a core wire of a high voltage line to a second lap point of a tested coupling capacitor; connecting a core wire of a CX end of an instrument to a third lap point of the tested coupling capacitor; introducing a signal of a vector value I of total current which flows through an upper section of the capacitor and a lower section of the capacitor into a high voltage end of a dielectric loss tester by the core wire of the high voltage line; and measuring a vector value IC2 of current which flows through the lower section of the capacitor by the measuring end CX of the dielectric loss tester, considering the vector IC1 of the current which flows through the upper section of the capacitor as vector difference between I and IC2, comparing amplitude and phase of the current with the amplitude and the phase of the current which flows through a standard capacitor and keeping the amplitude and the phase of voltage in test unchanged to measure the capacitances of the upper section of the capacitor and the lower section of the capacitor and dielectric loss. By the method, the capacitances of the upper section of the capacitor and the lower section of the capacitor and the dielectric loss value are simultaneously measured without disassembling a high-pressure lead or replacing a measuring lead.