Section 6(5)(b) in Tamil Nadu Electricity Regulatory Commission Tamil Nadu Electricity Distribution Code
(b)The capacity of step down transformers used in the distribution system and the layout of bus bars, switchgear, transformers, capacitors, earthing system, surge arrestors, control panels, station battery, fire extinguishers and other accessories required for the protection and safe operation of the substations shall as far as possible be standardized by the Licensees and shall conform to the guidelines and principles contained in the Code. The Commission, in specific cases and to ensure uniform adoption, can however specify the standards to be adopted.