Special Issues of Ensuring Electrical Safety in Networks with Isolated Neutral Voltage up to 1000 V at Mining Enterprises

Abstract

In the practice of operating mining machines and complexes, there are no effective ways to monitor the state of insulation and protect a person from electric shock in a network with voltages up to 1000 V. There is a risk of electric shock with a fatal outcome for personnel. Consequently, the issue of development of methods for monitoring the state of insulation and protection against electric shock in a network up to 1000 V for mining machines and complexes is relevant and urgent. The existing protection of a person from electric shock effectively works provided that the total insulation resistance is commensurate with the capacitive insulation resistance of the phases of the electrical network relative to the ground. But, at mining enterprises, a violation of ratio takes place between the total and capacitive insulation resistance of the network, which leads to failure of the protection against electric shock. Therefore, to ensure electrical safety criteria when operation of electrical installations in the network is up to 1000 V, it is necessary to consider the insulation condition and the technical capabilities of available protection against electric shock in a complex.

Mathematical description of the method for ungrounded AC systems to determine the network insulation

“…Susceptance of the network insulation characterizes the network capacity, that is, the number of connected electricity consumers and the length of overhead and cable lines [1,2].…”

“…Admittance of the network insulation depends on the zerosequence current and characterizes the magnitude of the singlephase earth fault current and the magnitude of the touch voltage in insulation damage [1,2].…”

“…For a better understanding of the material presented in this article, we give some necessary definitions. Conductance of the network insulation characterizes the insulating properties of the dielectric, the magnitude of the leakage current to earth [1,2].…”

“…Conductance of the network insulation characterizes the insulating properties of the dielectric, the magnitude of the leakage current to earth [1, 2].…”

"Approbation of the developed method for determining network insulation parameters on an operating excavator"

“…Due to the specific's mode of the quarry's electrical network, which is associated with the use of repeated short-term switching on energy-intensive motors, where the no-load currents rise in the shortest possible time to the latching currents [7][8][9]. All these oscillatory processes affect the deviations of the phase voltage values relative to the ground from the nominal values, thereby changing the zero-sequence voltage, which is directly dependent on the network insulation resistance.…”