Design and data processing of a real-time power quality monitoring instrument

Power quality(PQ) monitoring is an important issue to electric utilities and many industrial power customers. This paper presents a new distributed monitoring instrument based on Digital Signal Processing (DSP) and virtual measuring technology. The instrument is composed of EOC module, Feeder Control Unit(FCU) and Supervision Unit(SU). EOC module is used to implement the data acquisition and high speed data transmission of busbar voltage; FCU performs data acquisition and processing of feeders; SU based on virtual measuring technology is used to further analyze and process power quality parameters, achieves data storage and management. Wavelet-transformation which is implemented into SU detects transient power quality disturbance, while digital filtering, windowing, the software fixed-frequency sampling method, linear interpolation and Fast Fourier Transformation(FFT) are realized by DSP. Therefore, the monitoring instrument not only implements real-time, comprehensive high-precision and management for all power quality parameters, but also helps confirm source of the disturbance, improve the quality of power supply and increase the stability performance of power system.