Monitoring And Fault Diagnosing System For Power Capacitors Based On Synchronized Phasors

Power capacitors play an important role for maintaining balance of power system reactive power, maintaining stability of grid voltage and reducing power loss of transmission energy. Based on the analysis of existing method of line monitoring and diagnosis, the paper constructs the synchronized phasor based line condition monitoring and diagnostic system for power capacitors, which is important to protect power system’s economic security and stability.Firstly, the paper gives the calculation method of capacity, introduces the basic concepts of dielectric loss angle, and elaborates the theory of dielectric loss angle digital measurement method based on harmonic analysis, which provides a basic theoretical scheme for system implementation.The paper constructs the capacitor’s monitoring program, gives the GPS clock based synchronization phasor measurement method to ensure the strict synchronization of CT and PT measurement. Based on synchronization phasor, it also proposes Hanningwindowed Interpolated FFT calculation method for dielectric loss angle, so as to overcome the problems of calculating dielectric loss angle by FFT directly.The paper constructs the architecture of on-line capacitor monitoring system, and then proposes the decision rules’ based fault diagnosis method, which can diagnoses the capacitor’s general status by using the monitoring parameters including current, voltage, capacitance and dielectric loss angle.Lastly, we achieve the software system by Matlab and C#, and the system has a friendly interface to present the original waveform and analysis results. Then, On the basis of system running experiment, we analyze the cause of system errors, which lays a foundation for further optimization.