Computer based analysis of recovery voltage and residual fault currents for microcomputer based restructurable control of UHV transmission lines

Availability of sophisticated microprocessor technology at an exceedingly lower cost have made it possible to consider the implementation of more effective and sophisticated control schemes such as microcomputer based restructurable control schemes such as microcomputer based restructurable control of UHV lines as a means of improving the transient stability, increasing the power flow, and reducing the system disturbances during the presence of a fault. The restructurable control of UHV lines allows the disconnection of a minimum number of phases involved in a fault and requires autoreclosing of the disconnected phases immediately after the extinction of secondary fault arc. The success of restructurable control is a function of the secondary arc [2, 5, 16, 17, 22, 24, 25, 26, 27, 30, 31, 35, 36] the arc extinction time, mainly, depends upon the residual fault current and recovery voltage of the effective line length and voltage level of the healthy phases still retained in the system. In this paper computer based method for computing the recovery voltage and residual fault condition. For the case of balanced lines, similar expressions using the method of symmetrical components have been developed in a companion paper [6]. The method is generic, compact and for improved accuracy, utilizes the ABCD generalized circuit constants. The analysis includes the effect of line length, voltage level, swing angle, fault location, shunt inductive compensation, and the effect of isolated faults on differential and other protection algorithms. Using this method UHV lines ranging from 345-kv through 1500-kv have been simulated on a digital computer and the results have been discussed in a companion paper [7].