Experimental study on repetitive self-breakdown characteristics of a six-gap MV-class switch

Background Multi-gap gas switches offer unique advantages in reducing switch inductance, minimizing electrode erosion, and extending operational lifespans, making them a preferred choice for megavolt (MV)-class pulsed power systems operating in repetitive, long-duration modes.

Purpose This study aims to characterize and reveal the repetitive self-breakdown characteristics of a six-gap SF₆/N₂ mixed-gas MV-class switch. The goal is to design a high voltage (high current) and low jitter multichannel gas switch based on the repetitive overvoltage self-breakdown characteristics.

Methods The effects of gas pressure, repetition frequency, gas purge, and pulse count on the self-breakdown voltage distribution were investigated by experimental means, and the optimal self-breakdown voltage distribution under various operating conditions was identified. Detailed analysis of the self-breakdown voltage distribution characteristics was performed.

Results Results indicate that the normal distribution cannot adequately describe the self-breakdown voltage distribution under high-voltage, high-repetition-frequency, and long-duration operating modes. A mixture of normal distributions demonstrates better adaptability, with calculated mean and standard deviation values closely matching experimental measurements. However, the Weibull distribution exhibits the highest adaptability. Overall, for unimodal cases, the Weibull distribution is recommended, while for bimodal cases, a mixture of normal distributions is preferred. The gas purge system plays a critical role in maintaining stability during repetitive operation. Under high-repetition-frequency conditions, there exists an optimal gas purge velocity to minimize self-breakdown voltage jitter. Insufficient pulse counts in continuous operation fail to accurately reflect the true self-breakdown voltage distribution. As gas pressure increases, the self-breakdown voltage distribution transitions from bimodal to a unimodal Weibull-type distribution.

Conclusions The obtained results on repetitive self-breakdown characteristics of multi-gap SF₆/N₂ mixed-gas MV-class switch show a significant difference compared to the non-repetitive self-breakdown gas switch, which lays a foundation for the design of high-voltage, low-jitter gas switches for practical engineering applications.