Generator circuit breakers are breakers applied at a rated voltage matching the rated voltage of a generator in medium voltage system after generator.They are located between the generator and the step-up transformer.
In the 1960s generator circuit breakers were developed for the higher power ratings. Air blast technology was used, and the GCB s were equipped with an auxiliary switch and an opening resistor in parallel with the main interrupting chamber.
The opening resistors were necessary to reduce the zero crossing phenomenon and to decrease the rate of rise of the transient recovery voltage. In the late 1970s, generator circuit breakers with SF6 technology came on the market.Vacuum GCB it is now being use thanks to vacuum interrupter high technology manufacture for interrupting high value of current.
The common standard available worldwide that covers specifically the requirements for generator circuit breakers is IEC/IEEE 62271–37-013 (2015).
In above picture can see GCB sample from SIEMENS company used vacuum technology by rated current from 6300A to 12000A in medium voltage.
