Intermittent Grounding Fault Direction Detection Using Zero-Sequence Sign Comparison
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Solution Overview
Problem
Existing methods for determining the direction of intermittent grounding faults in power grids are inaccurate due to indeterminate transient durations of zero-sequence currents and voltages, leading to potential damage from incorrect fault direction determination.
Innovation Solution
A method that determines the direction of an intermittent grounding fault by comparing the sign of the maximum zero-sequence current with the sign of the maximum variation increment of the zero-sequence voltage, without capturing indeterminate transients, using a comparison module to assess if the fault is within the power line based on matching or opposing signs and preset rules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If phase angles between zero-sequence voltages of zero-sequence currents are used to determine fault direction, then the method can be implemented, but the fault direction determination accuracy deteriorates due to indeterminate transient durations
Solution Approach 1:
The patent changes the parameter used for fault direction determination from phase angles (which are affected by indeterminate transient durations) to the signs of maximum zero-sequence current values and maximum variation increments of zero-sequence voltage. This parameter transformation eliminates the influence of transient duration uncertainty and achieves accurate fault direction determination.
2Loss of information
If transient durations of zero-sequence currents and zero-sequence voltages are captured for analysis, then more fault information can be obtained, but the complexity of the determination process increases and accuracy deteriorates
Solution Approach 1:
The patent extracts only the essential features needed for fault direction determination - specifically the signs of maximum zero-sequence current values and maximum variation increments of zero-sequence voltage - while discarding the indeterminate transient duration information. This extraction approach simplifies the determination process while maintaining accuracy by focusing only on the relevant characteristics.
3Productivity
If incorrect fault direction determination occurs, then the determination process can be completed, but equipment damage or unnecessary line tripping may result
Solution Approach 1:
The patent employs a clear decision rule based on comparing the signs of maximum zero-sequence current and maximum variation increment of zero-sequence voltage. When the signs are the same, the fault is determined to be in the forward direction; when opposite, it is determined to be in the reverse direction. This feedback mechanism with explicit decision criteria ensures reliable and accurate fault direction determination, preventing incorrect actions.
Data Source
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AI summary
The present invention discloses a method and an apparatus for determining a direction of an intermittent grounding fault in a power grid. The method comprises: if an effective value of a zero-sequence current of a power line of a power grid is greater than or equal to a predetermined threshold, determining the maximum value point of the zero-sequence current (102); determining the sign (104) of the maximum variation increment of the zero-sequence voltage corresponding to the maximum value point; comparing the sign of the maximum variation increment with the sign of the zero-sequence current at the maximum value point and, based on the comparison result, determining whether the intermittent grounding fault is located in the power line (106). The present invention determines the direction of an intermittent grounding fault based on the result of a comparison between the sign of the maximum value of the zero-sequence current and the sign of the maximum variation increment of the zero-sequence voltage near the maximum value and solves the problem of difficulty in determining the direction of an intermittent grounding fault due to its indeterminate transient duration, thereby improving the accuracy of the fault direction determination.