Research Of Testing Principle Of Capacitive Current

With the densification of power load, and the application of cable line, the capacitive current of the medium voltage distribution network is bigger and bigger.When single-phase grounding fault occurs in the system, due to the increase of the capacitive current, arc discharge or resonance is much more likely to happen in the system, to affect the safety and reliability of operation of the distribution network. Therefore, the system operators need to master the status of the capacitive current, and to take measures. This paper research the testing principle of the capacitive current.First of all, this paper analyzed the measuring principle in theory of several kinds of distribution of capacitance current measurement methods,such as the single-phase grounding method, the neutral and capacitance method, three frequency method, vector method and so on, then simulate and research the above several measurement methods under the environment of Matlab/Simulink.Then this paper gives a comprehensive evaluation about the above several test methods, determines the vector method is the test method of the developed capacitive current test instrument.Considering the voltage signal, collected from the actual distribution network PT openings triangle side,containing voltage signal of feedback interference about thermal noise and harmonic, harmonic and so on,it requires the acquisition of voltage signal filter processing,for the accurate measurement of capacitive current of the distribution network.Based on the principle of adaptive noise cancellation, we designed an adaptive notch filter,which can accurately track the amplitude, frequency and phase of signal.At last,we make the simulation and verification for the adaptive notch filter,results show that the adaptive notch filter can accurately extracted the feedback voltage signal from PT openings triangle side,implement accurate measurement of capacitive current of the distribution network using the vector method.