Short-Circuit Detection in Case of the Cascade Shutdown of a Disabled Circuit in a Double-Circuit Power Transmission Line

This article supplements the previously published analysis of the informational contribution of the cascade shutdown of a power transmission line in the detection of a short circuit (SC) occurring in it. The recognizability of an SC with one-way observation of a line due to shutdown of the opposite side increases due to the disconnection of the opposite side, but the necessity remains to bring in complete information regarding phase values, including, which is undesirable, their components of the null sequence. It is shown that in case of a double-circuit power transmission line with bypass connection, the cascade shutdown of the damaged circuit opens up the new possibility in principle of estimating the voltage and current on its unobservable side. The situation arises in many but not all respects, recalling two-way observation of a damaged circuit. The main thing is that combined observation, just like ordinary two-way, can be performed in two-wire channels of phase values freed from components of the null sequence. The effectiveness is shown of the separation of the centered phase currents into two components: normal, determined in the model of an undamaged line, and local, operating in channels shunted from both sides. A measurement based on which the location of an SC is recognized is characterized by the a priori dependence on the line coordinate. Theoretical positions are illustrated using the examples of two-circuit lines, including actual power transmission with branches.