The switching of large power

THE GREAT GROWTH of power generation in the United States and Canada has imposed problems of control through switching operations that at times have seemed impractical, and the general progress in this phase of the industry seems to justify comment. With few exceptions our large systems, in contrast to continental European practice, are grounded, and line-to-ground faults become short circuits in which flow many times the normal power and which therefore must be removed instantly. As most high voltage lines are overhead and lightning over large areas of the United States is severe, the duty on switches and circuit breakers from such faults is frequently heavy. Moreover, as most line flashovers will clear themselves in a few cycles if the power flow is removed, we have resorted to fast reclosure, both single and polyphase, as well as to fast interruption, to maintain stable operation at high loads with a minimum number of transmission circuits and with heavy bus concentrations of generators. This is obvious to power engineers and is the basis for the necessity that American switchgear perform under heavy and frequent duty with absolute reliability. The improvement in this respect in recent years has contributed much to the continuity of electrical service and to its low cost, and is a tribute to the men who have worked, often under difficult conditions, with the abstruse phenomena involved. It is more than chance that five of the last six Lamme Medal recipients have been identified with important switchgear developments. In accepting the present award I wish to stress the broad co-operative effort in the industry on the part of many capable engineers, both in utilities and manufacturing, who have furthered this advance.