Abstract
For single-phase ground fault in resonant grounded power supply system, it is difficult to detect the fault line, while the existing methods have the shortcomings such as slow speed and large amount of computation. In our work the system natural oscillation wave contained in the zero sequence current is found to have opposite polarity and greater amplitude in fault line compared to that in non-fault line, and is proved to have a corresponding relationship with the first intrinsic mode function (IMF1) extracted from the same zero sequence current by empirical mode decomposition (EMD) of (Hilbert-Huang transform (HHT). Therefore, a new method for determining the single-phase ground fault line is proposed by finding the IMF1, extracted from the zero sequence current of each line by EMD of HHT, with the largest amplitude and opposite polarity compared to that of other lines. Meanwhile, EMD algorithm is improved to further enhance the fault detection rate based on the system natural oscillation wave's frequency and its attenuation trend in resonant grounding system. Simulation experiment and real data analysis indicate that the mentioned method is correct and fast.
Highlights
IntroductionAccording to the provisions of the national coal mine safety regulations, several voltage levels such as 10kV, 35kV and 66kV are adopted in large and medium sized mine power supply, and their operation mode of neutral point via arc suppression coil is referred to as small current grounded (resonant grounding system) power supply network
According to the provisions of the national coal mine safety regulations, several voltage levels such as 10kV, 35kV and 66kV are adopted in large and medium sized mine power supply, and their operation mode of neutral point via arc suppression coil is referred to as small current grounded power supply network
The Hilbert-Huang transform (HHT) mainly consists of two parts, that is, the first part is the empirical mode decomposition (EMD) proposed by Huang, which is used to decompose the signal into a number of specific components, called intrinsic mode function (IMF), and the second part is the Hilbert transform for each IMF
Summary
According to the provisions of the national coal mine safety regulations, several voltage levels such as 10kV, 35kV and 66kV are adopted in large and medium sized mine power supply, and their operation mode of neutral point via arc suppression coil is referred to as small current grounded (resonant grounding system) power supply network. Steady-state and transient line selection is the main research method, among them the methods such as zero sequence current amplitude comparison method, zero sequence current phase comparison method, amplitude and phase comparison method, are based on the steady component, which need long time to obtain fault signal and cannot identify the first fault line quickly in the actual application, and often cause wrong selection. This paper analyzes the zero sequence current caused by single-phase ground fault in resonant grounded power supply system and expresses it as a sum of different frequency signals. Fundamental wave method is based on the principle that the fundamental waves contained in the zero sequence current of the fault line and non-fault line have the characteristic of opposite polarity which can be seen from the Equations (2) and (3). The HHT mainly consists of two parts, that is, the first part is the empirical mode decomposition (EMD) proposed by Huang, which is used to decompose the signal into a number of specific components, called intrinsic mode function (IMF), and the second part is the Hilbert transform for each IMF
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