Realization Of DC System Insulation Monitoring Device Based On Fault Amplifying Method

Direct Current (DC) system is extremely important auxiliary power supply inpower plants and substations. Its reliability has direct impact on the security of theentire power system. The DC grounding is a common malfunction. It can not causeserious consequences when single point grounding fault occurs. However, it mayaffect the operation of the system when double point grounding fault occurs at thesame time. Single point grounding is not permitted for long time. Therefore, real-timeonline monitoring is necessary for DC system.This paper has analyzed the existing DC system insulation monitoring methods.In view of poor anti-jamming and low sensitivity of existing methods, a newinsulation monitoring device is designed based on Fault amplifying method. Underthe condition of ensuring system security, the device detection resistors are put intothe system by control switches, data is collected by the sensors and set to hostcomputer by CAN bus. The host determines insulation condition of the system bycalculating the insulation resistances. Secondly this paper introduces the systemdesign at two aspects about hardware and software. The hardware part is mainlydivided into main control module and sensor acquisition module. The two moduleshave adopted the C8051F040microcontroller as the core processor, its capacity islarge and processes speed is fast. Sensor acquisition module uses a self-designeddrain leakage current sensor for acquisition. The Software uses C language forprogramming. This paper introduces the main test circuit and software program flowchart. Monitoring the insulation condition of system accurately and high sensitivity ofthe device are verified by experiments and field operations. This device is perfectlysuitable for monitoring the DC system insulation of the power plant and thetransformer substation online.