NGR

why do you want to open the breaker? for any maintenance inside the breaker?...switch off generator and open.

Dear GYEST.

U should closed the breaker if u are in need for the generator to be a (stand by unit)

You should not open NGR after synchronisation with GRID to avoid stator earth fault but if you are running multiple genstes than in that case you may opt for switching on one only and reming are off to avoid tripping on circulating current..

if you have more than one generator at that time ony one ngr keep in line other are should be disconnected after synch. of generator

NGR is primarily installed to protected a certain equipment against ground faults.. you should take note the single line to ground fault during the time your generator is supplying the grid..

when the fault (ground faults occur in the gen bus), the NGR will lessen this current and thus also lessen the fault current in the stator thereby protecting your generator stator..

there are also other reasons you do such a thing for that, provide us with the generator configuration transformer configuration, and all system configuration.