Section 123 in The Indian Electricity Rules, 1956 states that Flexible cable exceeding 90 metres in length shall not be used with any portable or transportable apparatus, provided that such flexible cable when used with coal-cutting machines for long wall operation shall not exceed 180 metres in length, provided further that the aforesaid cable in case of an open cast mine, when used with electrically operated heavy earth moving machinery shall not exceed 300 metres in length.