Quantitative Mechanical Analysis of Power System Transient Disturbances

The quality of service that can be rendered during unavoidable system transients produced by short circuits must be given careful consideration in the analysis of proposed interconnection and transmission projects. An analysis of present systems that have grown until such limitations have apparently been reached, will frequently reveal comparatively inexpensive changes in equipment or operating practise which will permit good service to be given and defer large investments in additional lines for a considerable period. The fundamental mathematical methods for calculating system transients have been presented by other writers during the last few years. These mathematical calculations are of necessity qtite involved and consequently can only be applied to very simple power systems. The calculations must be made by thoroughly experienced engineers and the results are not readily understood by the operating staff. In the May 1926 issue of the Electric Journal, under the title ``A Mechanical Analogy to the Problem of Transmission Stability,´´ Mr. S. B. Griscom proposed the use of an accurate equivalent mechanical analogy to the electrical system provided perfect springs for representing line reactance could be obtained. A simple mechanical model for qualitatively illustrating the fundamental principles has been demonstrated before various local A. I. E. E. sections and has resulted in a wide general knowledge of the transient behavior of power systems. The present paper covers the adaptation of the mechanical model principles to obtain reasonably accurate quantitative records of transients to be expected on the 220-kv. interconnection between the Philadelphia Electric Co.