Section 6(5)(d) in Tamil Nadu Electricity Regulatory Commission Tamil Nadu Electricity Distribution Code
(d)Substation Design Criteria: HV substations, Sub transmission, primary and secondary distribution shall be designed taking into account the following factors:(i)Safety of Operating Personnel(ii)Adequate cross section of Busbar to meet the electrical and mechanical requirements.(iii)Mechanical and electrical interlocks to prevent inadvertent operation of equipments including switch.