A virtual instrument for diagnosis to substation grounding grids in harsh electromagnetic environment

To improve the traditional electromagnetic induction methods for grounding grid diagnosis, a virtual instrument is proposed to detect weak signals in the harsh and noisy substation electromagnetic environment. The induced electric signal in the coil of wire, containing multi-source and intense noises, is collected by the NI DAQ device. Then virtual phase intensive detectors and digital filters constitute the lock-in amplifier to suppress noise. In the experimental test, a small model of grounding grid is diagnosed in a man-made break situation. The visualized result shows the feasibility and accuracy of the proposed virtual instrument.