The Distance Protection and the Pre-Fault Conditions

In the present time in the Electric System of Power, in occasions you continuous using the distance function (21) as main protection in transmission lines what is not correct since the distance protection is affected by multiple phenomena, say you oscillations of power, effect of the mutual induction among lines, pre-fault conditions that can take to an incorrect operation of the protection, as well as the inability of simultaneous shot in both ends of the line that it protects. In this work the results of the mathematical analysis of a system are presented with lines of 110 kw where the phenomena and difficulties are evidenced that introduce to the distance protection taking alone in bill the negative effect of the flaw resistance and the conditions that existed before the flaw, as well as their possible solutions which are not completely effective.

Keywords: Distance Protection, Pre-Fault, Short circuit.