Question

The earth-lamps on a main switchboard comprise two , 240V 60W lamps connected in the usual manner. The potential difference at the busbars is 220V. Damage by sea water occurs to a distribution cable so that the insulation resistance to earth is reduced to 16Ω and 6Ω for +ve and - ve cables respectively. Find by calculation (a) which of the two lamps burns the brighter; and (b) the additional load on the generators occasioned by the fault. The resistance of the cables and the ship's structure may be neglected, and that of" the lamps taken as constant at the value corresponding to the 60W rating.