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A wavelet edge detection method is introduced to image the topology of grounding grids and locate the grounding conductors from measured magnetic induction. Theoretical analysis of the magnetic field and calculation method of discrete wavelet transform are described. Since the sharpest variation of the magnetic field perpendicular to the ground surface occurs right above a conductor, the gradient vector modulus maximum of the vertical component can be calculated to extract the position information about the conductor. This scheme is derived from the Canny edge detection. A 2-D discrete à trous algorithm is used to perform equivalent edge detection as the wavelet transform avoids partial derivative. The method is robust to noise and would extract more stable and distinct edge. Extensive simulation and experimental examples demonstrate that the proposed method can accurately draw the topology of grounding grids and locate the conductors. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Service lifetime estimation for earth grounding grids as a problem or a task faced by the industry is presented. A mathematical model based on Freschi's semianalytical model to determine the performance of the earth grounding grid at a certain year after being buried is proposed. The mathematical model can also explain the performance degradation of the earth grounding grid in principle and mathematically. According to the model, a scheme to estimate the service life of the earth grounding grid is proposed. A case study is given to illustrate how the scheme works. If the estimated service life of an earth grounding grid is not satisfactory, some measures, such as cathodic protection, should be considered to extend the service lifetime of the earth grounding grid. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]