Electrical Resynchronizing of a Large Cross-Compound Turbine-Generator Set: Part 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.