Resaerch Of On-line Monitoring System For Metal-oxide Surge Arrester

With the intellectualization of power grid,the real-time on-line state monitoring system,as an integral part of smart substation,is widely studied and used.MOA(Metal Oxide Arrester)is mainly used to protect the power equipment by releasing the over current caused by lighting,breaker operation,short circuit and etc.Its working condition is closely related to the security operation of power system.Thus,designing an on-line monitoring system to realize Life Cycle Management of MOA is very necessary.According to the research on simplified equivalent circuit of ZnO arrester,the characteristics of MOA's leakage current and some other influencing factors such as interphase coupling capacitance are analyzed.Through the in-depth analysis on several existing on-line monitoring methods,harmonic analysis method to monitor the leakage current is designed to be applied.In order to realize monitoring of arrester operation fortune,an electronic counter is designed to record the operating times for MOA.Thus real-time monitoring of MOA can be achieved by two function modules(leakage current monitor module and operating times counter module).To simultaneously monitor the leakage current of milliampere and the impulse urrent of hundreds ampere,the thesis developed a special lightning sensor.By means of combining the existing leakage current detecting techniques and MOA act counting technique,it can realize synthetic judgment of various parameters.Based on ARM LPC1114 processor,a scheme of on-line monitoring system is designed in the thesis.ARM LPC1114 is adopted as center processor according to the scheme.It realizes communication through RS-485.The hardware circuit is designed.PCB(Printed Circuit Board)manufacturing and functional debugging are accomplished.Based on requirements of system function,flow diagrams for subroutine and main program module are designed.RS485 buses based communication protocol between upper computer and site acquisition unit is provided.C Language Programming based on ARM LPC1114 is written and debugged.By C++Builder 5.0,a MOA monitoring information management system is designed.After processing by the lead circuit and center processor,through RS485 the signals collected at the scene are sent to the database monitored by the host computer to form statements.By the host computer,real-time on-line monitoring of MOA and analysis on the historical data can be realized.Experimental results show that the designed on-line monitoring system of arrester has good anti-jamming capability and can effectively monitor operating conditions.It provides a design scheme for on-line monitoring of capacitive equipment in smart substation.