Generator protection

Automatic circuit breaker is the first protection for the diesel generator against overload and short circuit faults; while it can be embedded with other protections for ground fault, voltage unbalance and frequency. It means that generator circuit breaker mandatory. And it is recommended to have a specific generator trip unit which can be adjusted thermally and magnetically (in case of thermo magnetic trip unite) and for solid state trip unite usually it is adjustable. Also, regarding circuit breaker no. of pole, it is recommended to be four poles to insure complete isolation for generator terminals.

Other protections can be offered for generator as following: –

Under/ over voltage

Under /over frequency

Earth fault 

Differential current

Reverse power (in case of multi sources)

and others

The following diagram shows some of recommended generator’s protections.