Design Of MOA Online Monitoring System

As an over-voltage protector, MOA produces aging and damp problems which needed to be monitored online in a periodical time. However traditional monitoring methods suffer spectral leakage and fence effect when the grid frequency shifts, bringing a large deviation to the result.To solve this problem, we propose a new method which combines phase measurement and harmonic analytical algorithm with windowed interpolation. Through the simulation to classic cosine windows, we choose Blackman cosine window to restrain the spectral leakage and combine Blackman window with bimodal interpolation. Results from simulation prove superiority and efficiency of the Blackman interpolation algorithm. Through the simulation, we select optimal hardware sampling parameters.Combining with the distributed monitoring the status of the MOA, we design an online monitoring MOA system which contains front monitor, middle collector and backstage onsite PC software. With the core of enhanced C8051F310microcontroller, monitor achieves the measure of full leakage current, fundamental current, third harmonic current, resistive peak current and capacitive peak current. Using C8051F020microcontroller as the core, collector make achievement of the extension of485network and the collection and transmission of network data. PC software design includes onsite debugging software and onsite monitoring software, which achieve the function of MOA data monitoring, historical data inquiry, and the fault location.The MOA online monitoring system designed in this paper performs well in the11KV MOA test. Results of the test show the accuracy, stability and efficiency of the designed system.