| This paper gives a design on high voltage power supply monitor for substation in coal mine on the base of analysis about existing condition and related production in domestic and foreign. A communication interface is designed in order to implement distance monitor with the help of computer. It can accomplish signal conversion from RS232 to RS485. The design selects a chip with optoelectronic isolated RS485 signal named MAX1480B which produced by MAXIM in America. By this means, the communication distance is increased. The intelligent collector is isolated from original synthetical protection device. It is controlled by singlechip together with voltage sensor, current sensor, temperature sensor and data-processing software to collect voltage, current, temperature, state of switch. At the same time, it performs control operation such as close switch, open switch, reset. In order to cut down checking period, a tributary station structure with double singlechips is designed. It is connected between computer and intelligent collector. It can implement both-way communication by a double-port RAM chip. In accordance, the system's whole performance got increase. Also tributary station which structures with a connecting link between the preceding and the following can work independently without host computer. At the same time, this paper also gives the design of multifunction software. The program consists of serial communication and data base procedure. The design makes full use of multiple communication modes between computer and many tributary stations. Unattended substation becomes true by these measures.
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