Permissible line lengths of up to 15 kV lines for microcomputer based selective control of UHV lines; digital simulation and results

The use of microprocessor technology to implement comprehensive control schemes such as microcomputer-based selective control of EHV/UHV lines is suggested. The permissible line lengths for single and selective phase switching, which depend on the residual fault arc currents and recovery voltages of the switched phases, are determined for UHV lines ranging from 345 kV through 1500 kV, for the first time, by simulating these lines on a digital computer. A computer-based method utilizing generalized ABCD line constants has been developed and mathematical expressions deduced for computing the residual fault current and recovery voltages. The results include the effect of line length, line voltage level, swing angle, fault location, and shunt inductive compensation on the recovery voltage and residual fault arc current