Effective grounding three-phase insulated electrical fire online prevention and control device and method

Abstract

The invention discloses an effective grounding three-phase insulated electrical fire online prevention and control device and method. The prevention and control device of the invention includes a DSPunit, a single chip microcomputer module, a photoelectric coupler module, an alarm unit, a control output unit, an Ethernet communication unit, a reset circuit module, a residual current signal detection module, a residual current signal conditioning circuit module, a voltage signal detection module and a voltage signal conditioning circuit module. According to the prevention and control method ofthe invention, the prevention and control device is used to decompose and restore the lumped residual current of the power supply circuit of an effective grounding three-phase AC distribution systemto all the phases, extract the resistive residual current component of each phase which truly characterizes the insulation characteristic and further calculate the resistive insulation resistance of each phase to ground. Thus, the insulation performance and potential electrical fire danger of the power supply circuit of the effective grounding three-phase AC distribution system are monitored online, and grounding short circuit faults and electrical fire accidents are prevented. The method of the invention can overcome the defects of conventional methods, such as false alarm, alarm failure andincapability of online detection.

Description

technical field [0001] The invention belongs to the field of electrical fire prevention and control, and relates to an effectively grounded three-phase insulation type electrical fire online prevention and control device and method. Background technique [0002] In the power supply circuit of the effectively grounded three-phase AC power distribution system, the insulation performance of the cable and load insulation layer, and the decrease of the resistive insulation resistance value to the ground will lead to grounding short-circuit faults and even cause electrical fire hazards, threatening people's lives and property safety. . [0003] At present, the common insulation-type electrical fire prevention and control methods for effectively grounded three-phase AC power distribution systems include the loop residual current method and the megohmmeter method. The loop residual current method is to monitor the lumped residual current effective value IR of the power supply loop ...

AI Technical Summary

Problems solved by technology

Due to the relative ground capacitive insulation resistance (C a ,C b ,C c ) formed capacitive residual current component (effective value is IRc a , IRc b , IRc c ) will change at any time with the length of the cable laying, the unbalanced degree of each phase line to the ground, the number of loads, the ambient temperature and humidity, and the service life. In larger cases, their vector sum (effective value is IR Z ) may still exceed the lower limit alarm threshold and cause false alarms. Similarly, although the resistive residual current component is large and the capacitive residual current is small, their vector sum (the effective value is IR Z ) still may not exceed the lower limit alarm threshold, resulting in the occurrence of missing alarms

The megohmmeter method is to use the megohmmeter instrument to measure the insulation resistance off-line after the power supply circuit of the effectively grounded three-phase AC power distribution system is cut off. Relatively resistive insulation resistance value is less than insulation resistance lower limit alarm threshold R 0 (set according to the actual situation of the construction site or the relevant national standards), it is considered that the power supply circuit of the effectively grounded three-phase AC power distribution system has a grounding short circuit fault and a potential electrical fire hazard, and this method cannot be monitored online. and potential electrical fire hazard disadvantages

Images