THE CONCEPT OF AUTOMATIC COMPENSATION OF CAPACITIVE LEAKAGE CURRENTS IN ORE-MINING ELECTRICAL NETWORKS

The exploitation of electrotechnical complexes, namely underground mining enterprises in particularly hazardous conditions are directly connected with necessity of protecting miners against electrical shock. Therefore ore-mining electrical nets with isolated neutral of the transformer are equipped with leakage current protection devices. However, in mine electrical supply networks semiconductor converters for regulating AC and DC in electric drives have been used for a long time. It transformed mine electrical supply networks to combined electrical supply networks that contain areas of commercial frequency, areas of DC and areas of variable frequency 0?70 Hz. The existing leakage current protection devices have been produced according to the requirements of GOST 22929?78, which is not applied in protection devices for combined electrical supply networks. Thus, the use of modern protection devices in mine combined electrical supply networks is unlawful. Leakage current protection devices with a working range of capacities from 0.0 to 3.0 uF has not been produced yet. A new method of capacitive leakage current automatic compensation based on usage of static throttle for limiting short - time currents in intervals is proposed. Short - time current in these intervals cannot exceed their norm value when the throttle makes a oscillating circuit with the capacity of the middle of the interval. To identify the working interval operating range of isolated network capacitance with its current value the operative current of high frequency is imposed on electrical supply network. Then coil windings switch over oscillating circuit with the capacity of the middle of the interval.