Thanks for sharing so in DC system relay will trip based on the change in voltage? And this relay functions differently from ac? Like in ac its induction but DC can not produce any induction. I am sorry for the basic stupid doubts but pls answer
Centre point of Battery Bank itself is not earthed. If you measure the voltage of positive terminal w.r.to Earth and negative terminal w.r.to earth under the condition battery is not connected with battery charger you would not get any voltage as there is no reference. Whenever battery Bank is connected to battery charger then only you will get equal half voltage w.r.to earthed. This is done mainly two reason one is to decrease the potential w.r.to earthed and another is it gives a returned path for earthed fault detection it may be positive to earth fault or it may be negative to earth fault.
