Research On Non-destructive Testing Of Round Steel In Grounding Grids Using Magnetostrictive Guided Waves

Substation ground grids are important facilities maintaining the security of thepower system. Ground grid conductors buried in the ground are prone to corrosion,endangering personal and equipment safety. Therefore, it is necessary to detect thehealth conditions of the grounding grids routinely. Up to now the detection methodsincluding large current analysis, grounding network node analysis, electromagneticmeasurement and electrochemical measurement, the performance of these methods isnot good enough for integrity evaluation of grounding grids. In this paper, a new kindof methods, using magnetostrictive ultrasonic guided wave technology, is introducedto the health detection of round steel used in industry of power system. The mainresearches include the following aspects:(1) Based on the magnetostrictive principle, designed a magnetostrictive guidedwave sensor. Using finite element simulation and experiment methods, analyzed theeffect of magnetic circuit number and structural to the bias magnetic field. Found theoptimized bias magnetic field for guided wave testing. According to time-spacepropagation characteristics of guided wave, designed sensor excitation time and space,and excited unidirectional guided wave using magnetostrictive sensor.(2) Wavelet transform method for extracting effective singular point informationin ultrasonic signal is applied to the notch width calculation. The simulation signalsand experiment signals are processed with wavelet transform method to achievequantitative detection of notch width.(3) According to the characteristics of the lap jointing round steel, studied onbending and horizontal lap jointing structures by simulation and experiment, analyzedthe transmission characteristics of guided wave in complex round steel structures.