Study And Design Of Protection Device For Mine-used Feeder Switch Based On ARM

Feeder switch is an important distribution equipment in underground minelow-voltage network. The security of low-voltage power supply system dependsmainly on the feeder switch. The main function of feeder switch is to detect electricalfaults in power system and protect the network when faults occurred. With thedevelopment of underground mine power supply system, the traditional feeder switchcannot meet the increasingly high requirements of the power supply system forsecurity, reliability and continuity. The protection of the traditional feeder switch isnot quick enough and improvements of its reliability and stability are urgent.Therefore, study and development of new high-performance mine-used feeder switchprotection device is very necessary.For the branch power supply networks with isolated neutral, a new integratedprotector of mine-used feeder switch which is based on ARM Cortex-M3processorand μC/OS-Ⅱ embedded operating system is developed in this paper. Thisprotection device which includes a variety of functions such as detection, control,fault protection, communication and so on can solve the existing problems oftraditional feeder switch.Firstly, the causes and detection methods of various faults are analyzed on thebasis of the detailed description of the status and development trend of mine-usedfeeder switch. Targeted protection methods are put forward. The two states ofthree-phase short-circuit and motor starting are distinguished effectively bycomparing their power factor. A new formula of inverse time overload protection isdevised to solve the problem of greater delay deviation of traditional method. Theimpact of the distributed capacitance of electrical wire in coal mine is considered inthe level two selective leakage protection system and adjustment measures ofzero-sequence current setting value are devised to improve the flexibility of leakageprotection. And RS-485communications technique is used to reduce the action timeof selective leakage protection. The accuracy of phase measurement in phasedetection of leakage protection is improved with all-phase Fourier algorithm. Secondly, ARM chip STM32F103RB is used as the control core and the designsof main circuits are analyzed in the hardware design. The software system is basedon μC/OS-Ⅱ embedded operating system, and modularization programming methodis adopted to design the system tasks and develop the software. The software systemhas advantages of well real-time and flexibility. During design, the reliability of thesystem is improved by using a variety of anti-jamming measures.Finally, an experimental platform modeled on the underground low-voltagepower supply system is set up for functional tests. The results showed that theprotection device can make effective and reliable protection.