DESIGN AND LAYOUT OF EXTRA HIGH-VOLTAGE SUBSTATIONS (400, 500, 750 K V )

Abstract

Electrical Engineering is the life and blood of industry. The country advances with rapid industrialization. The power resources of our country are: 1) hydro 2) Thermal 3) Nuclear The country's hydro power potential is 41 million kilowatts. The estimated fuel resources for thermal and nuclear are about 50,800 M.tons of coal and 30,000 M.tons of thorium. Out of which only certain portions are now being utilized. During last decade the installed capacity has been increase to 400%. The peak demand during 1966-67 was 6166 ~IW as against the 1971-72 demand of 1)+,106 M-watts. Thus there is substantial increase in power demand. As per estimates of Ministry of Irrigation and Powe3(India) the power demand may touch a peak of +8,000 M-watts by, 1980-81. To meet the demand, it is necessary to investigate, plan and construct the major power projects. For increasing generating capacity and its effective transmission, it is necessary to increase the transmission capacity. To strengthen the transmission system and to transmit bulk power, over long distances extra high voltage transmission is the only alternative. Adoption of extra high voltage transmission necessitated the, construction of extra high voltage sub-stations for trans-formation and distribution of power to load centres, In the transmission system, the capital investment on the substation is predominative. Substantial amount has to be spent on the equipment such as power transformers, circuit breakers, disconnecting switches, current transformers, potential transformers and protective gear. Any slight saving in the cost in sub-station, will give substantial reduction in capital investment. Savings in sub-station can be achieved by the selection of proper equipment, the judicial fixing of insulation levels of equipment, selection of proper busbar arrangement giving due consideration to utmost reliability. For selection of insulation levels of equipment, it is necessary to study the various over voltages of the system. A critical review of over voltages and its control has been made. Statistical methods has been used in fixing the withstand strength of air insulation. The electrical clerances have been worked out as per the latest CIGRE. Report. They are compared with past practices. Internal insulation level of the transformer has been fixed duely co-ordinating with the protective level of lightning arrester. Self co-ordination of breaker insulation has been given up. .Longitudinal and transverse insulation of breaker and disconnecting switches have been co-ordinated with the arrester characteristics. A 500 KV step up sub-station, transformer station and a switching sub-station have been designed based on the latest literature in this field.