Prime-Mover Speed Governors for Interconnected Systems

Abstract

System operating requirements, from the standpoint of frequency and tie-line loading, are continually becoming more rigorous and receiving more widespread attention. Supplementary controls have been developed to assist in the solution of these problems — but the speed governors of the prime movers still constitute the backbone of system control. This paper outlines the general problems encountered; gives definitions of terms for both steam and hydro governors and discusses the performance characteristics of these two general classes of prime movers. As a result of discussions with several operating groups certain definite conclusions were reached for prime-mover governor characteristics on the larger systems, viz., dead band should be as small as practicable; uniform incremental regulation desirable; adjustable regulation not necessary; similar rates of response not necessary and accurate response to supplementary control desirable. These conclusions are supported by the analytical work presented in the companion paper.7 A summary of the reasoning supporting these conclusions under the subjects of stability, dead band, regulation, response, short circuits, and tie-line swings is included. Introduction During the past several years the interconnected power system has come into being and has expanded rapidly to the point where some of these systems now comprise several million kilovolt-amperes of connected capacity. Many problems have appeared and of these, two important and closely associated ones, speed and load control, have continued to receive increased attention. In most cases large portions of these systems are tied together by tie lines of relatively small capacity and as a result power flow across the ties must be carefully controlled. Frequency control is being widely used in varying degrees of refinement and automatic tie-line control is being used in more and more locations.1,12,13,14 The control associated with these two problems is usually applied in the form of relatively slow supplementary adjustments to the normal action of the basic speed governors, which still constitute the backbone of system control. It is logical, then, as system operation becomes more refined and the requirements more rigorous, that more attention2,3,4 be given to the characteristics of the speed governing mechanisms. During this same period special instruments8,9,10 for accurately measuring small changes in system frequency have been developed and these instruments have been used to advantage by several groups in analyzing governor performance.