390 / 2017-04-25 13:59:48

Test Analysis of Dielectric Recovery Characteristic in High Voltage SF6 Circuit Breaker

high voltage circuit breaker; ,SF6;,dielectric recovery characteristic;,breakdown voltage; ,polarity effect;

In this paper, dielectric recovery characteristic during operation of high voltage SF6 circuit breaker is studied by test method. The test circuit of dynamic breakdown characteristics is built. Circuit breaker closing and opening dynamic breakdown voltage curves under positive and negative polarity are obtained. Impact of inflatable pressure and closing speed to dielectric recovery characteristic are analyzed. Breaking dielectric recovery rate and closing pre-strike time under different experimental conditions are given. In terms of the chamber structure of the circuit breaker, the breakdown voltage difference between the positive polarity and negative polarity is not large when the opening distance is within 7mm, during this period the polarity effect is not obvious. However, the breakdown voltage of the positive polarity is larger than that of the negative polarity when the opening distance is greater than 7mm, which means that the "reverse polarity" effect shows up during this period. Besides, the closing speed has great influence on the closing pre-breakdown characteristic, the maximum value of the breakdown time is 1.18ms when the closing speed is 6.6m/s, while the maximum value is 2.21ms when the closing speed is 4.7m/s. So increasing the closing speed is an effective way of controlling the pre-breakdown time. Breakdown voltages of the opening and closing processes increase as the gas-charged pressure of the chamber increases, and the pressure influence on the closing breakdown voltage is greater than on the opening breakdown voltage. The possibility of the repeated breakdown exists within 0.5ms and 1ms after the contact separation when the gas-charged pressure is 0.7Mpa and 0.5MPa, respectively. For this reason, arc-extinguishing should be avoided during these time periods of the opening process.