Abstract
The corrosion diagnosis of grounding grid can locate the corroded branches and provide guidance for the maintenance and repair of the grounding grid. This paper proposed the electrical impedance tomography (EIT) method on the corrosion diagnosis of grounding grid and described how it works. Firstly, the inverse problem model of the electrical impedance tomography on grounding grid is developed. Secondly, in order to weaken the ill-posedness of the inverse problem, a Newton iterative algorithm with Tikhonov regularization is proposed to solve the problem. Then, due to the high resistivity contrast between the soli and steel and the large size of imaging region, this paper presents the method of soil-separation and block-diagnosis to accomplish these problems. Finally, field experiments were carried out to verify the effectiveness of the proposed method and the results show that the location and degree of the corrosion in the grounding grid can be easily judged from the imaging results.
Highlights
Grounding grid is an important part of electrical power system at substation for the discharge of dangerous current and safety of persons working at substation [1]
Based on the topology of grounding grid obtained by derivative method [17] or wavelet edge detection [18], we proposed soil-separation and block-diagnosis methods to improve the diagnosis accuracy
It is found that the corrosion fault of the grounding grid can be accurately diagnosed by electrical impedance tomography (EIT) and the image is straightforward to judge the location of the corrosion, accurately diagnosed by EIT and the image is straightforward to judge the location of the corrosion, which is not depended on the shape of the grounding grid block
Summary
Grounding grid is an important part of electrical power system at substation for the discharge of dangerous current and safety of persons working at substation [1]. In the study so far, the diagnosis method based on electric network theory regard the branch as a resistor but do not consider the distributed parameter of the grounding grid, for example the resistivity, Energies 2018, 11, 1739; doi:10.3390/en11071739 www.mdpi.com/journal/energies. Utilized the magnetic field above the grounding grid to reconstruct the resistivity distribution image to find the break-point of the branch. Due to the different resistivity between the corroded and the normal steel, the corrosion diagnosis of the grounding grid is potentially feasible through the resistivity distribution image obtained by EIT. Similar to the medical EIT, the grounding grid EIT implemented by injecting a current into the grounding grid and measuring the potentials of the down-lead lines and use the data to reconstruct the resistivity distribution image. Simulations and field experiment are carried out and the results show the corrosion degree and corrosion location in the branch of grounding grid can be achieved correctly
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