Resonance conditions in power supply systems of coal mines

Abstract

The publication presents the results of research into occurrence conditions of resonance phenomena in underground power supply systems of coal mines. These studies are due to significant losses of electricity in the underground electrical networks of coal mines owing to resonance phenomena. In terms of unfailing performance and overall reliability for consumers, including high-productivity coal mines and the whole power supply system, the resonance phenomena pose a significant danger and, therefore, must be damped. The main technological unit which governs the stable operation of a coal mine is an extraction site, which is in spotlight in this article. An equivalent circuit is created for the power supply system of an extraction site was developed, including the equivalent circuits for the main process equipment: a shearer, an armored face conveyor, a crusher and a reloader, which are the sources of harmonic components and aid the resonance phenomena. After some transformations, a simplified equivalent circuit was obtained to assess the resonance phenomena of currents and voltages in underground electrical networks, and some dependencies were revealed to determine the conditions for their occurrence, and most importantly, to find the possibility of their damping in underground electrical networks. The implemented research allows determining a number of aspects that form the network topology and the structure of the underground power supply system, which makes it possible to: exclude the possibility of resonance; reduce power losses and extra heating of electrical equipment. This can have a beneficial effect on the safe operation of the power supply systems, reduce downtime, and, consequently, cut down the cost of coal mining.