Research And Measurement On DC Circuit Breaker Arc Vacuum Dielectric Strength

The development of HVDC technology makes the research on DC circuit breaker more and more deeply. The continuous improvement of voltage grade put forward higher request about the performance of DC circuit breaker. DC vacuum circuit breaker has been widely used due to its strong opening ability. The dielectric recovery strength of arcing chamber is closely related to the performance of circuit breaker. Therefore, the research of dielectric recovery is an important direction in the field of vacuum switch. The method of active auxiliary circuit is applied in the paper, which creates artificial zero of current, thus open circuit DC circuit breaker.Arc model was established based on MTALAB software in this paper, and system circuit is simulated, and current waveform of high frequency and low frequency parts is acquired. Besides, arc voltage and current transform waveform is acquired from the results of the simulation. The ball gap trigger circuit, Rogowski coil and integrating circuit is designed in this paper. High frequency part is led to the main circuit by the ball gap trigger circuit.After the zero current point of DC circuit breaker, it is required that a power source is applied to the vacuum arcing chamber if dielectric recovery needs to be measured. The main circuit of high voltage pulse power which voltage, pulse number and pulse interval can be adjusted is designed in the paper. BUCK circuit is simulated in the process and some parameters are acquired. The inverter circuit is particularly simulated, and bias phenomenon has great influence on the output waveform. Different methods are taken, which finds blocking capacitor can effectively reduce the bias phenomenon. In addition, upper computer procedure is designed in this paper, output parameters of the pulse power can be easily controlled by PC, which improve the efficiency and safety.Experiment platform is built based on existing laboratory equipment, and DC fault current is substituted by LC oscillation circuit. Dielectric recovery measuring circuit is improved, which separates the active device and circuit breaker after zero current point. Thus, only high voltage pulse power is applied to the both sides of the arcing chamber, which makes accurate measurement results. In zero current point of DC circuit breaker, while the current is zero, there are still lots of residual particles. Based on the zero current point, high voltage pulse power is applied to the both sides of the circuit breaker’s contacts in different times, and different breakdown voltage corresponding to different times is acquired by oscilloscope. Experimental data is recorded and large errors are excluded. The data is processed to fitting by using Matlab software, thus the vacuum arcing chamber dielectric recovery strength curve is obtained. The dielectric recovery time of the arcing chamber is about 17μs, and the rising rate is about 0.88kV/μs.