Research On Monitoring Technology For Performance State Of Intelligent Overload Relay

The motor is widely used in electrical power system. With the development of modern computer technology and microelectronics technology, motor protection technology is gradually transiting to intellectualization. Compared with traditional relay, the intelligent overload relay has some advantages. But during the long life process, the loss of the parts will appear to lead to the change of protection performance of the intelligent overload relay. When the loss accumulates to a certain level, the protection performance will be unstable, even the protection failure will occur. Therefore, research on monitoring technology for performance status of intelligent overload relay becomes important.In this paper, the analysis on the principle of operation principle and interior structure of a kind of typical intelligent overload relay is carried out. Multi-signal model analysis method is adopted in the performance monitoring of intelligent overload relay. The sensitive parameters of the protection performance are determined and the relationship between the signal states and the module failure states is established. The hardware and the software of the real-time monitoring system are designed with PIC microcontroller as the core. The hardware system of monitoring system includes acquisition circuit of the voltage of power module, the power current of microcontroller chip module, the contact resistance of execution module, the voltage of transformer module and the voltage of signal processing module of intelligent overload relay, the display circuit, the power protection circuit, and so on. The software system is designed with C language in PIC and with LABVIEW in PC to realize the functions such as data acquisition, dispose, state evaluation, display, communication, etc. In addition, error analysis is carried out from the aspects such as A/D conversion precision of single chip, measurement accuracy of instrument and the parameter dispersion of the components. By real-time monitoring, the function state and the fault part of intelligent overload relay can be found as soon as possible. The replacement of the failure product can be finished in time and the protection reliability of the power system can be improved.