Section 2(1)(x) in The Orissa Electricity Reform (Transfer of Assets, Liabilities, Proceedings and Personnel of Gridco to Distribution Companies) Rules, 1998
(x)"Transmission System" means the system, consisting of electric lines having design voltage of 66 KV or higher, which is used for the purposes of the transportation of electricity from one power station to a substation or to another power station or between substations or to or from any external interconnection including 33/1 KV bays/equipment (up to the interconnection with any Distribution System), any plant and apparatus and meters owned or used in connection with the transmission of electricity and such buildings or part thereof as may be required to accommodate such plant and apparatus and other works and the operating staff thereof.