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Circuit breakers for boulder dam line
754
CURREP~T
TOPICS.
[J. I;. I.
Circuit Breakers for Boulder Dam Line.--( Elec. Engrp., Vol. 54, no. 4.) D. C. PRINCE of the General Electric Co. describes the theory, construction, and tests of the new type circuit breaker to be used on this 275 Kv. transmission line 270 miles long from Boulder Dam to Los Angeles. To secure the maximum through power under fault conditions, the two parallel tower lines are united and sectionalized at two desert switching stations located respectively 90 miles from each end of the line. At each switching station and Kva. circuit at sending and receiving stations four 2,500,000 breakers are to be installed, so connected that in the event of a fault anywhere on the line, only one 90 mile circuit need be cut out. Power then will be transmitted over the remaining 90 mile single circuit and 180 miles of two circuit line. The new oil blast breaker was developed for high speed operation, 3 cycles from initiation of tripping impulse to interruption of circuit; its small oil volume is 2500 gallons or about I/IO that of an equivalent breaker of conventional design. The oil exposed to arcing is only about 210 gallons or I per cent. of that exposed in an equivalent conventional breaker. Two interrupting elements are provided, each containing four breaks and a piston to furnish the oil blast. A complete 3 phase unit of this design weighs approximately I 10,000 pounds as compared with 290,000 pounds for a tank breaker. While the interrupting rating of this 287 Kv. breaker is 2,500,00o Kva., in a test made on one break at a voltage 50 per cent. higher than one break can receive in service, 3800 amperes was interrupted. R. H. 0.
CURREP~T
TOPICS.
[J. I;. I.
Circuit Breakers for Boulder Dam Line.--( Elec. Engrp., Vol. 54, no. 4.) D. C. PRINCE of the General Electric Co. describes the theory, construction, and tests of the new type circuit breaker to be used on this 275 Kv. transmission line 270 miles long from Boulder Dam to Los Angeles. To secure the maximum through power under fault conditions, the two parallel tower lines are united and sectionalized at two desert switching stations located respectively 90 miles from each end of the line. At each switching station and Kva. circuit at sending and receiving stations four 2,500,000 breakers are to be installed, so connected that in the event of a fault anywhere on the line, only one 90 mile circuit need be cut out. Power then will be transmitted over the remaining 90 mile single circuit and 180 miles of two circuit line. The new oil blast breaker was developed for high speed operation, 3 cycles from initiation of tripping impulse to interruption of circuit; its small oil volume is 2500 gallons or about I/IO that of an equivalent breaker of conventional design. The oil exposed to arcing is only about 210 gallons or I per cent. of that exposed in an equivalent conventional breaker. Two interrupting elements are provided, each containing four breaks and a piston to furnish the oil blast. A complete 3 phase unit of this design weighs approximately I 10,000 pounds as compared with 290,000 pounds for a tank breaker. While the interrupting rating of this 287 Kv. breaker is 2,500,00o Kva., in a test made on one break at a voltage 50 per cent. higher than one break can receive in service, 3800 amperes was interrupted. R. H. 0.