On-line Monitoring For Mechanical Characteristics Of Vacuum Circuit Breaker

On-line monitoring for mechanical characteristics of vacuum circuit breaker is the precondition of predicting maintenance, is the key element of reliable run, and is the important supplement and updated development to the traditional off-line preventive maintenance. Advances in measuring and testing technology continue to provide more reliable and efficient methods for on-line monitoring of mechanical characteristics of vacuum circuit breaker. The greatest emphasis on monitoring for mechanical characteristics of vacuum circuit breaker should be placed on the operating mechanism. In this paper, the principle and the special ways of on-line monitoring for mechanical characteristics of vacuum circuit breaker are introduced, and test results are also analyzed.Firstly, the Hall current sensor that sensitive to instantaneous signal is used to monitor the current signal of close (open) coil in the operating mechanism, Linear variable differential transformer (LVDT) displacement transducer of DC (direct current) with a higher accuracy, is adopted to measure mechanical displacement signal of movable contact, and converts it into the synchronous voltage signal. In this paper a new single chip microprocessor PIC16F877 made by Microchip Company, is regarded as the core in whole system, and the peripheral hardware interface circuits are designed, which includes input of sensor, handling of analog signal, A/D conversion, input and output of switching value, expansion of I/O port and data storage device, design of keys and nixie display, the serial communication between the single-chip microprocessor and personal computer, design of power supply etc, and the software program is compiled by assemble language. The communication standard between the master computer and the subordinate computer adopts RS485 serial communication interface agreement, which can transmit accurately the acquired data to personal computer that will display the waveshape and process the data. Thus the mechanical characteristic parameters of vacuum circuit breaker can be calculated, for example, close (open) time, average speed, length of travel, overtravel, etc. Furthermore, some measures of anti-interference are taken, thetechniques in hardware design consist of isolation, earth connection, shielding, wave filtering, etc. The techniques in software design consist of order redundancy, watchdog timer, wave filtering of slipping average value, etc. At last, Visual Basic language is used to accomplish design of man-machine interface and display of test waveshape.With the rapid development of sensor technology, signal processing technology, the microelectronic technology and computer communication technology, on-line monitoring technology for mechanical characteristics of vacuum circuit breaker will get more consummation and improvement, which will promote development process of intelligent circuit breaker. The development of on-line monitoring technology for mechanical characteristics of circuit breaker will be the key to successful development of intelligent circuit breaker.