Interpretation of NSDD and Restrike in Capacitive Current Switching Test on Medium Voltage Vacuum Circuit Breaker


G. Venkateswarlu
Yugal Agarwal
M. S. Takkher
M. K. Wadhwani
B. M. Mehra


Capacitor banks are installed in an increasing number to control power quality issues and improving the power factor to
counteract the reactive power in the transmission and distribution networks. Due to load fluctuations switching of capacitor
banks is a typical phenomenon. Capacitor bank is normally having concentrated capacitance in contrast with distributed
capacitance. It generally draws more current than unloaded cableor line in practical cases up to several hundred amperes.
Hence, switching of capacitor bank causes a very high rate of rise of transient recovery voltage across circuit breaker
contacts. This scenario can be simulated in testing laboratories by a voltage source connected to a circuit breaker which
again is connected to a large capacitance in terms of IEC called capacitive current switching test. Non-sustained disruptive
discharge (NSDD) is a voltage breakdown after the vacuum circuit-breaker open the fault current which will not cause the
recovery of power frequency current. Restrike is different from NSDD, the recovery of power frequency current between
the contacts will make the breaker failed. It’s not easy to show the distinction between NSDD and restrike during some type
tests. The paper presents the study of performance evaluation of the circuit breaker during the capacitor current switching
duties. A statistical analysis of failure of circuit breaker during capacitor current switching tests are included in the paper
to help the manufacturers & utilities, so that the care can be taken for trouble free services. The paper also discusses the
changes made in the IEC 62271 – 100, Amendment1:2012 for conducting the capacitive current switching tests.


How to Cite
Venkateswarlu, G. ., Agarwal, Y. ., Takkher, M. S. ., Wadhwani, M. K. ., & Mehra, B. M. . (2022). Interpretation of NSDD and Restrike in Capacitive Current Switching Test on Medium Voltage Vacuum Circuit Breaker. Power Research - A Journal of CPRI, 17(2), 81–87.


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