A New Automatic Load Control for Turbine Generators

In an interconnected power system, load changes of sufficient magnitude to affect system frequency are normally shared by all the generators on the system in proportion to their ratings and the characteristics of their governors. This inherent sharing of load changes is highly desirable in the majority of cases. It may, however, present a problem in a few instances if some of the generators are remote geographically and electrically from that part of the system which includes a large fluctuating load. In such cases it would sometimes be preferable if the load changes could be confined in whole or in part to the local generators, thereby relieving the remainder of the system from having to respond to distant load fluctuations. This situation may become acute in the case of systems interconnected through long tie lines, where abrupt load changes in either system result in large transfers of synichronizing power through the interconnecting ties. This paper describes a new automatic load control arrangement which has the ability to respond to local load changes in anticipation of their effect on system frequency. At the same time, however, it does not deprive the conventional speed governor of its ability to control the prime mover input to help maintain constant system frequency. In this latter respect lies its essential and unique difference from other somewhat similar arrangements described previously.^1,2,3