# A High-Impedance Grounding Fault Identification Method for Mining Cables in Non-Effectively Grounded Systems of Coal Mine Power Grids Based on Steady-State Impedance Analysis–Holmes–Duffing

## TL;DR

This paper introduces a new method for identifying high-impedance grounding faults in coal mine power grids using steady-state impedance analysis and a Holmes–Duffing oscillator for weak signal detection.

## Contribution

The novel method combines steady-state impedance analysis and a Holmes–Duffing oscillator to improve fault line selection accuracy in non-effectively grounded systems.

## Key findings

- The proposed method uses zero-sequence current phase differences to identify faulted lines accurately.
- The Holmes–Duffing oscillator enables effective detection of weak signals in mining environments.
- Case studies confirm the method's effectiveness in improving fault identification despite interference and measurement challenges.

## Abstract

What are the main findings?
This paper proposes a steady-state impedance analysis (SSIA) method. By utilizing the stability of steady-state signals in the distribution network, fault characteristic analysis becomes more convenient.A Holmes–Duffing oscillator-based small-signal detection method is proposed, which enables effective measurement of weak signals.

This paper proposes a steady-state impedance analysis (SSIA) method. By utilizing the stability of steady-state signals in the distribution network, fault characteristic analysis becomes more convenient.

A Holmes–Duffing oscillator-based small-signal detection method is proposed, which enables effective measurement of weak signals.

What is the implication of the main finding?
By using the difference in zero-sequence current of each line before and after a fault as the fault criterion, fault line selection becomes more accurate.Image processing is applied to the phase diagrams output by the oscillator. Case studies demonstrate that the proposed method improves the measurement capability for fault line selection. Fault identification is not affected by measurement accuracy, resulting in more precise fault detection.

By using the difference in zero-sequence current of each line before and after a fault as the fault criterion, fault line selection becomes more accurate.

Image processing is applied to the phase diagrams output by the oscillator. Case studies demonstrate that the proposed method improves the measurement capability for fault line selection. Fault identification is not affected by measurement accuracy, resulting in more precise fault detection.

In coal mine non-solidly grounded systems, high-impedance faults generate minimal zero-sequence currents with obscured characteristics and strong interference, complicating faulted line identification. Existing methods rarely address three-phase imbalance and variable cable parameters, causing selection errors. To this end, a method for identifying the non-effective ground fault routing of mining cables based on Steady-State Impedance Analysis (SSIA) and Holmes–Duffing oscillator small-signal detection is proposed. Firstly, based on SSIA, the mapping relationship that the phase of the zero-sequence current variation in the faulted line is the same as the phase of its voltage relative to the faulted ground is derived before and after the occurrence of the fault. Meanwhile, identifiable differences exist in both phase and amplitude of the zero-sequence current change in faulty lines compared to non-faulty lines before and after fault occurrence. This is used as the criterion for high-impedance ground fault line selection. In the mining environment, zero-sequence current variations are characterized as weak signals, which poses significant challenges for detection. Thus, a Holmes–Duffing oscillator weak signal detection method is proposed. Based on chaotic principles, accurate line selection is achieved by diagnosing chaotic states in oscillator-generated phase trajectories. A specific mine grid simulation via MATLAB/Simulink 2023b validates the method’s efficacy and applicability.