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# Wiring principle of capacitive Voltage Transformer

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Working principle of capacitive voltage transformer

Capacitive voltage transformer is essentially a capacitor divider. For the sake of analysis, the capacitor string is divided into two parts: main capacitor C1 and voltage divider C2, as shown in the upper left figure. If the relative ground voltage on the primary side is U1, then the. The voltage is:

UC2=C1/(C1+C2)U1=KU1. The ratio of C _ 1 / C _ 1 + C _ 2 is the partial pressure ratio, and different partial pressure ratio can be obtained by changing the ratio of C _ 1 and C _ 2. Because the UC2 is proportional to the primary voltage U1, the measurement of UC2 can get U1, which is the principle of capacitive voltage transformer.

The main reason of capacitive voltage transformer is that the output end of capacitor voltage divider can not be directly connected with the instrument, otherwise, the secondary load impedance will affect its accuracy. The function of the protective gap is that when the abnormal overvoltage occurs on the voltage divider capacitance, the gap first breaks down to protect the compensator, the voltage divider capacitor and the intermediate transformer from being damaged by the overvoltage.