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In addition to its importance as a itching station, the substation maintains optimum bus voltage to provide the best possible service to customers- A synchronous condenser, manufactured by Elliott Company, maintains a suitable voltage on the 115-kv system. However, the station bus voltage is not the controlling factor since loads are not served directlv from the Beaver Creek in stallation. Rather, the distribution substations on the network are the ; points at which approximately con stant voltage is needed. The over-all system voltage can be adjusted over a considerable range by the operator at the substation. Power generated in the ColoradoBig Thompson Project's hydro-elec tric power plants on the eastern slope of the Rocky Mountains is de livered to the Beaver Creek sub station over Bureau transmission lines extending through Greeley and Brighton, Colorado. From the sub station, the power continues over a network of 115-kv lines radiating out to Sterling, Colorado (where inter connection is made with the Missouri River Basin transmission system) and Holyoke, to Akron, Yuma, Wray, and Limon, all in northeastern Colorado. These lines supply energy for dis tribution systems operated by REA co-ops and municipalities. Three of the II 5-kv lines may cither supply power or represent loads, depending on system operat ing conditions. These lines emanate from the Beaver Creek installation and extend respectively to Greeley, the Colorado-Big Thompson Project substation at the Flatiron Power and f'bmpmg Plant, and a Missouri River asm Project substation at Sidney, -Nebraska. The remaining lines ^supply distribution substations only. ;? Beaver Creek installation's V 5-kv bus structure is designed to seven 115-kv transmission JS, one 46-kv line, and the sul> SS^VW.OOO.kva, 13.8-kv syn Diagram uj northeastern Colorado H5-kv transmission system an which the Heaver Creek substation is located near the toad renters. The system is supplied by several hydro stations. An Elliott 35,000-kva, -tjO-rpm generator series the Pole Hill Power Plant. Three Elliott 13,333-kcu, JJO-rprn generators are installed in the Kories power plant in the Kendrick Project, mentioned at top of diagram, and two Elliott 18,950-kva, ICyl-rpm generators will soon be in operation at the Aleeva power plant, also part oj the Kendrick Project. chronous condenser. Two of these 115-kv line positions are spares for future expansion of the ColoradoBig Thompson Project power system. In addition to the main bus, the sub station is equipped with a 115-kv transfer bus. With the exception of the bay serving the transformer for the 46-kv line, there is one 115-kv oil circuit breaker for each line position. The 46-kv line is protected by a 46kv oil circuit breaker and the 3-phasc transformer is protected by 115-kv fuses. An additional 115-kv breaker is installed between the 115-kv bus supplying the transformer bank and the transfer bus, serving as a transfer breaker if any 115-kv breaker is taken out of service. Three single-phase, 115-kv, grounded wyc to 13,800-volt trans formers arc installed in the switch yard to supply the synchronous con denser. Each transformer has a sclfcooled rating of 12,800 kva, which can be increased to 16,000 kva by the addition of cooling fans. Initially, network analyzer studies indicated that the bus ac the sub station should be maintained at about 107 kv during periods of light loads. These studies also showed that the voltage should be increased to about 115 kv during periods of heavy system loads. During periods of light loads, the capacity of the trans mission lines tied into the substation causes the voltage to rise at distant POWERFAX. SPRING 1951 PAGE l