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What does class C1 or C2 mean for a HV circuit breaker ?
IEC 62271‐100 define separate test duties for switching of unloaded cable or line and switching of capacitor bank.
The breaking currents in each duty depend on the rated voltage and are in range of few tens of Amps (for cable and line switching) and up to 400 A in case of capacitor bank switching. Furthermore, inrush current of 20 kA and inrush frequency of 4250 Hz are defined for back‐to‐back capacitor bank switching.
Finally, it is distinguished between two classes of restriking probability:
circuit-breaker class C1
circuit-breaker with low probability of restrike during capacitive current breaking as demonstrated by specific type tests.
eg : protection function
To protect capacitor banks with a low frequency of operations.
The circuit breaker closes and opens on the capacitive current of the bank very seldom.
circuit-breaker class C2
circuit-breaker with very low probability of restrike during capacitive current breaking as demonstrated by specific type tests.
eg : operation function
Introduce in the new standard (IEC 62271-100) due to the requests of the HV users.
The circuit breaker operates the capacitor banks very often, one per day for instance