The effects of frequency dependence, line asymmetry, and varying ground conductivity on ultrahigh speed, travelling wave based, single ended, protection schemes are investigated in this paper. Typical schemes assume the transmission lines to be balanced and frequency independent which simplifies the analysis of the fault transients. Investigation of a single circuit vertically configured transmission line reveals that better results can be obtained by using modal parameters based on the configuration of the transmission line. The problem of modal mixing at discontinuities on the transmission line is demonstrated in the case of an unbalanced line to ground fault. The results described in this paper have applications in both protection and fault location schemes.
Read full abstract