Huang Daochun

Study on dynamic voltage distribution characteristics of modular triple-break vacuum circuit breaker

In order to get the dynamic voltage distribution characteristics of U-shaped triple-break vacuum circuit breaker based on 40.5kV fiber-controlled vacuum interrupter modules and give references for choosing suitable dynamic voltage-sharing measures, synthetic breaking tests with low voltage and small current were firstly carried out. The transient recovery voltage(TRV) of the three breaks were measured and the results indicate that, the dynamic voltage distribution characteristics after small current interruptions are close to those of static state, the peak transient recovery voltage distribution of the break at the high voltage terminal is more than 60% and 1000pF grading capacitors can satisfy the voltage sharing requirement of breaking small current. Based on the “Continuous Transition Model”, a transient equivalent model of the triple-break vacuum circuit breaker was built by PSCAD/EMTDC and the TRV distribution characteristics and main influence factors after high current interruptions were analyzed. The simulation results indicate that the dissipative processes of residual charges have big impacts on the dynamic voltage distribution, and the synchronism among breaks should be pay attention to in the large current interruption tests followed.

Study on the icing flashover characteristics of porcelain double sheds suspension insulator string

In the present paper, study on icing flashover characteristics were carried out in artificial climate chamber of State Grid Electric Power Research Institute (SGEPRI) with XWP2-160 porcelain double sheds suspension insulators. According to IEEE Task Force on insulator icing test methods the natural freezing rain condition was simulated and 3 to 7 units XWP2-160 insulators were icing energized at service voltage. Based on the tests results, the U50% increases with an increase in dry arcing distance linearly for XWP2-160 not more than 7 units. The effect on icing flashover performance of the factors such as ice thickness and applied water conductivity were investigated respectively. More over, ice states and discharge process of insulators icing energized were compared with the de-energized ones and discussed. For the air gaps can enhance the electrical strength of iced insulators, the U50% withstand voltage of insulators icing energized is higher than the de-energized ones.