ELECTRICAL RESYNCHRONIZING OF A LARGE CROSS-COMPOUND TURBINE-GENERATOR SET .I. ANALYTICAL STUDY

The procedure for returning a cross-compound set to the line following load rejection and loss of excitation is complicated by the diverging “coast-down” characteristics of the two turbine-generators. The first phase of a resynchronizing procedure is to bring the speeds of the two generators to the same per-unit value. This paper presents the analytical study of the resynchronizing process, specifically as it was applied to Commonwealth Edison Company's Will County no. 4 set. The two-pole 332-MVA and four-pole 308-MVA units were successfully resynchronized from a range of speed differentials up to 0.4 pu by applying rated open-circuit field excitation to one unit. The major consequences of this asynchronous duty are manifest in 1) rotor surface eddy currents, and 2) pulsating currents, voltages, and torques. Direct instrumentation of the eddy currents and pulsating torques was not practicable during the field tests, therefore the duty was analyzed and monitored in terms of terminal characteristics. Comparisons between test and calculated results are given, and conclusions drawn regarding the parameters that govern the effects of the resynchronizing process. Copyright © 1969 by The Institute of Electrical and Electronics Engineers, Inc.