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过电流保护在煤矿井下电气安全中起着极为重要的作用。过流保护和漏电保护、接地保护一起,被称为井下电气三大保护。井下低压电网过电流保护的执行,低压馈电开关起着极为重要的作用。但这种开关在井下长时期使用,设置在固定设备峒室内,一用甚至好几年,使其整定值和实际动作值间存在较大误差。这种误差无法掌握,时间越长,差值越大,往往会使低压电网的过流保护出现误动作,甚至不动作。为解决这一普遍性问题,我们自制设备,对井下低压馈电开关作了误差测定,并进行了准确度校核。根据煤炭工业部制定的《矿井低压电网短路保护装置的整定细则》的规定,保护干线馈电开关的过电流继电器的电流整定值,按下列规定选择:
Over-current protection plays an extremely important role in the electrical safety of coal mine. Over-current protection and leakage protection, ground protection together, is called the three underground electrical protection. Low-voltage underground power grid overcurrent protection implementation, low-voltage feed switch plays a very important role. However, this type of switch is used for a long time downhole and is installed in a fixed equipment and used for even several years, resulting in large errors between its setting value and the actual operating value. This error can not be mastered, the longer the difference, the greater the value, often make the low-voltage power grid over-current protection malfunction, or even action. In order to solve this universal problem, we made self-made equipment to measure the error of underground low-voltage feed switch and carried out the accuracy check. According to the provisions of “Detailed Rules for Setting of Short-circuit Protection Devices for Low-voltage Power Network of Mine” formulated by the Ministry of Coal Industry, the current setting of the overcurrent relay for protecting the main feeder switch should be selected according to the following rules: