一、引言近年来,随着煤炭工业的迅速发展,采掘机械化水平在不断提高,用电设备的单机功率及井下用电负荷有了新的变化。采煤机单机最大功率由原来的80千瓦增加到300～400千瓦,双机功率已达到2×375千瓦,一个采区的负荷由原来的500千瓦左右增加到1000～1500千瓦左右。一个年产400万吨的 I. INTRODUCTION In recent years, with the rapid development of the coal industry, the level of mining mechanization has been constantly increasing. There has been a new change in the stand-alone power consumption and the underground electricity load of the electric equipment. The maximum power of single machine of shearer increased from 80 kilowatts to 300 ~ 400 kilowatts, the power of double machine has reached 2 × 375 kilowatts, the load of a mining area increased from about 500 kilowatts to about 1000 to 1500 kilowatts. An annual output of 4 million tons