Research On Characteristics Of Electric Energy Metering System Transferring Dynamic Signal

In modern power system, the process of generation, transmission, distribution and usage of power electric is always under dynamic state. The pattern of signal-generating under dynamic state is different from it under steady state. The design and verification of electric energy metering system are under steady state. Without considering the error of measurement device, when dynamic signal is the input signal, the accuracy of measurement is decided by the distortion of the transfer process.Signal made-up under dynamic state is analyzed in this thesis. The dynamic signal is consist of sinusoidal signal and decaying DC component. Spectral analysis is taken for decaying DC component and the spectrum shows continuous and the proportion of low-frequency is large. It is shown that dynamic signal will be distort through linear system when simulation analysis is performed.Second, the analysis of the frequency characteristics of the electric energy metering system transfer process is started. The electric energy metering system is divided into linear transfer process and non-linear transfer process according to the different type of mutual inductors. Linear transfer process is made up by linear mutual inductor, secondary circuit and filters. While the non-linear one is made up by electro-magnetic inductor, secondary circuit and filters. Since the result of signal transfer is decided by the frequency characteristic of the system, the frequency characteristic under linear transfer process and the non-linear transfer process is studied respectively. The frequency characteristic of linear transfer process shows a non-linear feature, especially the remarkable non-linear feature of phase-frequency characteristic. The frequency characteristic of non-linear transfer process also shows a non-linear feature. The frequency band is narrow than the one in linear transfer process, a band-pass character is shown.Based on the study of dynamic signals and the frequency characteristics of the power metering system transfer process, simulation analysis is performed for dynamic signal transfer process in electric energy metering system. It is indicated that the error of transfer process of measuring system will be increased by dynamic signal, with the larger proportion of decaying DC component and greater time constant, the error will larger on the same time. From the aspect of frequency characteristic, the method of decreasing error is found. The idea of using zero phase-shift filters is put forward in this thesis. Simulation example shows that zero phase-shift filters has the effect on decreasing the error of linear transfer process.