The First 230 KV Underground Oil Filled Cable Project in IRAN

For supplying Electrical Energy to meet every day increasing demand of utilities with high density population in down town of Tehran, the optimum solution is considered to establish a 230 KV underground cable network. This network consists of connecting five substations by four different routes as Bessat S/S through Shush S/S to Ghourkhane S/S, Azadegan S/S to Ghourkhane S/S, Mossalla S/S to Ghourkhane with one circuit of 400 MW transmission capacity.The 230 KV oil filled cables are installed in concrete tunnel with clear dimensions of W 1.5 in, H 2.5 m and made of prefabricated reinforced concrete pieces, in five types to provide route crossings and bending radius, for two circuits of 230 KV cables and four circuits of 63 KV cables.Arrangement of 230 KV cables in tunnel were made possible with assembling a complete set of, aluminum alloy, stainless steel, galvanized metal accessories for spacing and fixing of cables and joints.230 KV cables are chosen to be single core low pressure oil filled with 1600 sq.mm copper conductor of six segmental compact, stranded circular type.Insulation are made of highly pure KARFT-PULP papers with low pressure oil. Metallic sheath is of corrugated seamless aluminum, covered with P.V.C as outer jacket. Oil feeding, monitoring and control of oil pressure are done by considering route profile and operation conditions in transient and normal cases and using oil tanks and stop joints to set specified oil pressure in each oil section. Grounding and bonding of metallic sheath has been done through cross bonding system. Construction works of this project were started in February 1988 and by energizing of one circuit of 230 KV cables from Bessat S/S through Shush S/S to Ghourkhane S/S and Azadegan S/S to Ghourkhane S/S on June 1994 and February 1996 respectively, the high density load centers of Tehran Metropolitan in down town are feeded with 230 KV voltage for first time.