scope:

This part of the IEC 62146 series is applicable to grading capacitors used on circuit-breakers. Their function is to control the voltage distribution across the individual interrupter units of a multi-break circuit-breaker.

Grading capacitors can also be used in parallel to the interrupter unit on single break circuitbreakers to modify the Transient Recovery Voltage (TRV).

The grading capacitor is a sub-component for the circuit-breaker and shall be specified in accordance with the circuit-breaker specifications.

This standard applies to grading capacitors falling into one or both of the following categories for:

− mounting on air-insulated circuit-breakers;

− mounting on enclosed circuit-breakers (for example immersed in SF6, in oil, etc.).

The testing for each of the above applications is in some cases different.

The object of this standard is:

− to define uniform rules regarding performances, testing and rating;

− to define specific safety rules;

− to provide a guidance for installation and operation.

NOTE CIGRE Technical Brochure 368 [2] presents a study about the operating environment of voltage grading capacitors applied to high-voltage circuit-breakers.

This standard does not apply to phase-to-earth capacitors installed on the circuit-breaker to modify the Transient Recovery Voltage.