Search

As a non-invasive imaging method, electrical impedance tomography (EIT) technology has become a research focus for grounding grid corrosion diagnosis. However, the existing algorithms have not produced ideal image reconstruction results. This article proposes an electrical impedance imaging method based on sparse representation, which can improve the accuracy of reconstructed images obviously. First, the basic principles of EIT are outlined, and the limitations of existing reconstruction methods are analyzed. Then, an EIT reconstruction algorithm based on sparse representation is proposed to address these limitations. It constructs constraints using the sparsity of conductivity distribution under a certain sparse basis and utilizes the accelerated Fast Iterative Shrinkage Threshold Algorithm (FISTA) for iterative solutions, aiming to improve the imaging quality and reconstruction accuracy. Finally, the grounding grid model is established by COMSOL simulation software to obtain voltage data, and the reconstruction effects of the Tikhonov regularization algorithm, the total variation regularization algorithm (TV), the one-step Newton algorithm (NOSER), and the sparse reconstruction algorithm proposed in this article are compared in MATLAB. The voltage relative error is introduced to evaluate the reconstructed image. The results show that the reconstruction algorithm based on sparse representation is superior to other methods in terms of reconstruction error and image quality. The relative error of the grounding grid reconstructed image is reduced by an average of 12.54%.

A grounding grid plays the role of discharging current and balancing voltage to ensure the safety of the power system. However, soil corrosion can damage the grounding grid, which then can endanger the safe operation of power system. This paper reviewed recent research advances of soil corrosion of grounding grid. The cause, mechanism, types, and influencing factors of soil corrosion of grounding grids were summarized, and the corresponding detection technology and protective measures were also introduced. The paper pointed out that soil corrosion is a serious threat to the grounding grid system. Moreover, the impact mechanism of AC stray current, new corrosion detection technology, and better protective measures still need in-depth research.

The grounding device plays performs the role of releasing a lightning current and a fault current in the power system, and the corrosion of the conductor will cause damage to the grounding body, which threatens the safe operation of the power system. The grounding grid corrosion detection technology and equipment guarantee the safe operation of the power system. This paper discusses the research status of grounding corrosion and topological detection in detail and introduces the basic principles, research difficulties and existing problems of the methods such as the electric network method, electromagnetic field method, electrochemical method, ultrasonic detection method and electromagnetic imaging method. The methods of electromagnetic imaging and time difference positioning proposed in recent years have been also discussed in detail. The paper points out that the application of grounding grid corrosion detection distance engineering still faces great challenges and that multi-disciplinary, multi-information fusion, new sensing technology, big data platforms and intelligent computing will be the trends to follow in research on grounding grid fault, corrosion detection and life prediction.

The grounding grid is critical to the safety and stability of a power system. Corrosive cracking of the grounding conductor is the main cause of deterioration of grounding grid performance. Existing fault diagnosis methods for grounding grids are limited by the number and distribution of grounding leads, and some of them cannot be used for online detection. This paper proposes a grounding grid detection method based on magnetic source excitation. The measuring device consists of four coils, two horizontal excitation coils, and two vertical receiving coils. The secondary magnetic field signal is extracted from the primary field and the background field by properly positioning the coils, such that the measured signal can reflect the underground media more accurately. The measuring device of the method is portable, the measurement process is contactless with the grounding grid, and it is not limited by the grounding leads. Furthermore, it has a strong anti-interference ability and can realize online detection. It was proven by simulations and experiments that the proposed method has a higher measurement accuracy and stronger anti-interference ability when compared with existing methods. This paper also discusses the influence of various factors such as the number and the location of the breakpoints, the frequency of the excitation source, the soil resistivity, and stratification from the measurement data. It was proven that the method has high precision and a wide application range, and is important for guiding significance and reference value in engineering applications.

The grounding grid of a substation is important for the safety of substation equipment. Especially to address the difficulty of parameter design in the auxiliary anode system of a grounding grid, an algorithm is proposed that is an optimization algorithm for the auxiliary anode system of a grounding grid based on improved simulated annealing. The mathematical model of the auxiliary anode system is inferred from the mathematical model of cathodic protection. On that basis, the parameters of the finite element model are optimized with the improved simulated annealing algorithm, thereby the auxiliary anode system of a grounding grid with optimized parameters is structured. Then the algorithm is proven as valid through experiments. The precision of the optimized parameters is improved by about 1.55% with respect to the Variable Metric Method and the Genetic Algorithm, so it can provide a basis for parameter design in the auxiliary anode system of a grounding grid.

The grounding grid is a key part of substation protection, which provides safety to personnel and equipment under normal as well as fault conditions. Currently, the topology of a grounding grid is determined by assuming that its orientation is parallel to the plane of earth. However, in practical scenarios, the assumed orientation may not coincide with the actual orientation of the grounding grid. Hence, currently employed methods for topology detection fails to produce the desired results. Therefore, accurate detection of grounding grid orientation is mandatory for measuring its topology accurately. In this paper, we propose a derivative method for orientation detection of grounding grid in high voltage substations. The proposed method is applicable to both equally and unequally spaced grounding grids. Furthermore, our method can also determine the orientation of grounding grid in the challenging case when a diagonal branch is present in the mesh. The proposed method is based on the fact that the distribution of magnetic flux density is perpendicular to the surface of the earth when a current is injected into the grid through a vertical conductor. Taking the third order derivative of the magnetic flux density, the main peak coinciding with the position of underground conductor is accurately obtained. Thus, the main peak describes the orientation of buried conductor of grounding grid. Simulations are performed using Comsol Multiphysics 5.0 to demonstrate the accuracy of the proposed method. Our results demonstrate that the proposed method calculate the orientation of grounding grid with high accuracy. We also investigate the effect of varying critical parameters of our method.

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.