Research on the Application of Ultra Low Frequency Excitation Sources for Corrosion Detection of Grounding Grids
It is proposed to use ultra—low frequency sources instead of DC,power frequency,or high—frequency AC sources to excite the grounding grid.Based on the electrical network theory method,the resistance of the grounding grid and its branches is measured,and then the corrosion of the grounding grid is judged.Theoretical,simulation,and real ground grid experiments have shown that using DC excitation to measure ground grid resistance is appropriate without electrical interference;When using alternating excitation to measure the grounding grid,the increase in frequency and mutual inductance between branches affect the acquisition of grounding grid resistance.The experiment shows that the proportion of power frequency impedance in impedance is 15.8%,and the AC resistance is larger than the DC resistance.The electrical interference simulation test on the ground grid shows that interference at the same frequency as the excitation source can lead to larger measurement errors in the ground grid impedance.Under 10 A DC interference,the input resistance error of the true ground grid measured by DC excitation reaches 10.63%.Using an ultra—low frequency 0.1 Hz excitation source to measure the ground grid impedance,the resistance component is equal to the DC resistance,and the proportion of inductive impedance is about 0.19%.In engineering,the ground grid impedance can be used as its resistance at this time,and the ultra—low frequency excitation can effectively resist electrical interference.The maximum error in measuring the input impedance of the unfiltered ground grid is 2.35%.Therefore,ultra—low frequency excitation sources are suitable for measuring the resistance of the ground grid and determining its corrosion.
grounding gridultra low frequency power supplycorrosion detectionapplicability
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