The grounding grid plays an important role in the safe and reliable running of substation, The study on detection and fault diagnosis of grounding grid will provide an effective means for its state evaluation. This paper proposes a multiple parameter imaging method for grounding grid by pulsed electromagnetic inverse, that aims at accurate positioning and quantitative evaluation of corrosion and breakpoint for power system grounding grid, and the new method intends to realize the image reconstruction of electrical conductivity, permittivity and structure for grounding grid. Using the characteristics of electromagnetic wave propagating in different medium surface, the new method establishes the mathematical-physical model and analyzes the electromagnetic field propagation characteristics between grounding grid and the surrounding medium.

Faults of grounding grids are threat to the safety of power system and cause significant economic loss every year in China. Accurate detection of the faults will alleviate these detrimental effects. This paper presents a novel approach using the transient electromagnetic method for fault diagnosis of grounding grids. The induced magnetic intensity is collected by receiver coils in the form of electromotive force. After inversion calculation, the contour map of equivalent resistivity of underground covered by grids is obtained. The faults due to corrosion or break can be accurately located from the distribution characteristics of equivalent resistivity maps. The influence of the fault of different degrees, material of grounding conductor, and soil resistivity on distribution of induced magnetic intensity to fault diagnosis will be analyzed in detail. The effect of the underground pipeline on fault diagnosis of grounding grids is also investigated. Simulation was performed, and a field experiment was conducted to verify the effectiveness of the proposed method.

Faults in the grounding grid are hidden danger to the safety of power system and cause significant economic loss every year. This paper presents a new means to locate faults in grounding grids using the transient electromagnetic imaging method. The method compares the distribution characteristics of the equivalent resistivity of underground covered by grids for no fault case and those with break points. We describe why and how the proposed method can be used for break point diagnosis of grounding grids. Simulation was performed using Ansoft FEM package, and a field experiment was conducted to verify the effectiveness of the proposed method. This study provides a practical means for break point diagnosis with no requirement of power shut down or soil excavation. Moreover, the proposed method does not require the design drawings of grounding grids.

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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.