Study On Distributed Monitoring System For Transient Electromagnetic Disturbance In Substations

The transient voltage, transient current, transient magnetic field, transient electric field,which generated by the operation of disconnectors and breakers in substations ,will cause disturbance problems on the secondary equipments .It is very important to study on the mechanism and characteristics of transient electromagnetic disturbance, with the prerequisite of accurately acquiring its waveforms. At present, there is not a realtime monitoring system widely running in substations. Therefore, it is needed to develop one. This thesis analyses electromagnetic coupling method of the transient disturbance, discribes the switching process of the disconnectors. It will produce a group of pulses. The limitation of traditional measurement schemes is analyzed. The Circuits based on high pass filter are designed for extracting the transient disturbance signal. Using virtual instrument platform for the monitoring system, the hardware structure diagram is proposed, and the trigger mechanisms is analyzed when transient disturbance occurs. Its software flow chart can be divided into data acquisition, data storage, waveform query, waveform subsets extraction and re-sampling, computing the power spectrum, basic parameters measurement, filtering processing, generating reports module. In order to validate the feasibility of the monitoring system, system integration and experiment was made in the laboratory. The two kinds of hardware circuit all can accurately extracts disturbance signal to trigger the acquisition system when transient disturbance occurs. Then it can record the waveform and the precise time. Especially, when transient disturbance signal couples into the steady-state voltage and hasn't exceed its peak voltage, the circuits can also capture the disturbed signals which traditional measuring instrument cannot by edge trigger. By increasing absolute value detection, the HPF circuit can trigger the system when it automatically runs, regardless of transient pulse polarity is positive or negative, the circuit can transform it into single polarity, realizing automatic capturing transient disturbance for the system. The availability and reliability is proved by the experiment.