Generator field overvoltages due to energizing lines

The field current transient characteristics are studied in the paper when generators energize transmission lines under no-load. The tendency of reverse current induced in field circuit is explained. Taking into account the effect of rotor eddy currents, a transient equivalent circuit of generator is presented. A generator energizing a 500 kV long line under no-load is simulated using the EMTDC program. The simulation results demonstrate that large reverse voltages may occur in field circuit and happen easier than the phenomena of self-excitation and switching surge overvoltages, and that the 4-quadrant excitation system can avoid the large reverse voltages.