Section 73(2)(b) in The Indian Electricity Rules, 1956
(b)The low voltage circuit of the step up transformer shall contain a manually operated control device having overload protection in addition to the over-current device for circuit protection, and these devices shall have no exposed live parts and for diagnostic work there shall be an additional switch in the said circuit, which shall be of one of the following types:-(i)a switch with a spring or other mechanism that will open automatically except while held close by the operator, or(ii)a time switch which will open automatically after a definite period of time for which it has been set.