Transmission at 30,000 Volts

EDITORIAL.

TRANSMISSION AT 30,000 VOLTS.

In discussing the proposed use of 33,000 volts on the transmission circuits of the Southern California Power Company, it was observed in those Columns some time since that "not a well grounded doubt has been expressed but that the undertaking will be crowned with success," and that the use of this high voltage for transmission purposes is now feasible is no longer a question of belief alone, for during a recent experimental run lasting three days, a potential as high as 30,000 volts was used continuously in actual work, under most trying climatic conditions. The experiment was made over the circuits of the Pioneer Electric Power Company of Ogden, under the direction of Mr. F. O. Blackwell, chief engineer of the power transmission department of the General Electric Company, and Mr. L. S. Boggs, electrical engineer of the Pioneer Company, from whom the following details of the experiments were derived.

A double pole line of three No. 1 wires extends from the powerhouse in Ogden Canon to Salt Lake City, a distance of 36 miles. The transformers at the power-house and substations in Salt Lake City are connected in delta and are operated at a potential of approximately 15,000 volts at the powerhouse. For the purpose of experiment, however, these transformers were changed over from the delta to the star connections, and the electromotive force of the generator was also increased until a pressure of 30,000 volts was delivered to the line. At Salt Lake City the ends of the transmission lines was thus returned to the power house and delivered to a hank of three 250-kilowatt transformers which reduced the line pressure to 2,300 volts. This arrangement gave a transmission of seventy-three miles over which a load of 1,000 horse-power was delivered to the resistance vats at the power-house. The minimum potential delivered to line was 27,880 volts, during winch 23,000 volts pressure was delivered from the return circuit at the power-house. The water rheostats consisted of three wooden tanks, each measuring eight feet in length by three feet in depth by four feet in width. These tanks were placed five feet apart and mounted each on three double petticoat, deep groove glass insulators. The electrodes consisted of 3-8th sheet steel of such size as to give one inch clearance on all sides.

The loss in the transmission was measured by watt-meters inserted in both ends of the lines so as to include that due to the transformers (which together amounted to 4 per cent) and the maximum loss thus derived was 9.9 per cent. "There was no loss of voltage to speak of," writes Mr. Blackwell, "the capacity of the line (the periodicity is 60 cycles) being sufficient to compensate for the potential [inductive (?)—Ed.] drop." Mr. Blackwell further states that not the slightest difficulty of any kind developed during the entire seventy-two hours covering the test. During the experiment for a period of a day there was also taken from the circuit at Salt Lake City, at a pressure of 24,000 volts, a load of 500 horse-power consumed in operating synchronous motors.

To continue to quote from Mr. Blackwell's letter: "During this period there was the worst possible weather--rain, fog and snow alternating, with no trouble whatever, and in addition there was a severe thunder and lightning all of one night, during which the lightning arresters discharged repeatedly without causing even a flicker in the light circuits."

At the conclusion of the experiments the transformers were changed over from "Y" to delta windings, and since then the plant has been running at 15,000 volts as originally designed.