Capacitive Inrush Current Capabilities of -SF6 Switchgear

This paper discusses the series of tests performed to demonstrate that for SF6 and other gas switchgear, the inrush current frequency on capacitor energization or pre-restrike is much less important than the current magnitude and often does not need to be limited. Also, the inrush current magnitude alone may not need to be limited. The limiting parameter is the ICI (Inrush Current Integral) during the pre-arc time during a making operation, before galvanic contact of the contacts is achieved. As a result, the formerly used i x f product (or di/dt) as a limitation for switchgear is less of a concern. This paper discusses the testing performed on high voltage SF6 circuit breakers to demonstrate this phenomenon and provides guidance in applications where the formerly used i x f limitation is exceeded.

Automated summary

This paper discusses the testing conducted on SF6 circuit breakers, demonstrating that the frequency of inrush current during capacitor energization or pre-restrike is not as significant as the current magnitude and often does not require limitation. The ICI (Inrush Current Integral) during the pre-arc time is the limiting parameter, rather than the previously used i x f product. The paper provides guidance for applications that exceed the former i x f limitation.