Generator Stability at Low Excitation

The addition of static capacitors for power factor correction on the 4-kv distribution circuits of the Chicago, Ill., system has resulted in the operation of generators at power factors close to unity during light load periods. This introduces a problem of generator stability at low levels of excitation. It is the purpose of this paper to present the results of a study on the behavior of the generators on the Chicago system during these light load periods, and to show to what extent capacitors may be added to the system without resorting to capacitor switching. The paper shows that loss of generator field presents the most serious problem in the operation of generators during such light load periods. The results of this analytical study indicate that the generators on the Chicago system may be operated safely at high power factors.