Harmonic-Based Phase-to-Earth Fault Location in High-Impedance Networks
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Solution Overview
Problem
Existing fault localization algorithms in electric networks face accuracy issues due to the combined effect of load current and fault resistance, particularly in high-impedance earthed systems and when loads are not exclusively tapped at the end of the feeder, leading to inaccurate fault location estimates.
Innovation Solution
A method that compensates for errors in both voltage and current quantities using impedance-based fault localization, calculating load-compensated zero and negative sequence currents and voltages to determine the location of single-phase earth faults in unearthed, compensated, and high-impedance earthed networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance-based fault localization algorithms are used in high-impedance earthed systems, then fault location can be determined, but accuracy deteriorates due to the combined effect of load current and fault resistance
Solution Approach 1:
The invention transforms the fault localization approach by changing the parameters used for calculation. Instead of using standard impedance-based methods with fundamental frequency quantities, the invention utilizes harmonic components (specifically the 2nd harmonic of zero-sequence voltage and 3rd harmonic of zero-sequence current) to create a fault location calculation that is insensitive to load current and fault resistance effects. This parameter transformation resolves the contradiction by finding alternative measurement parameters that eliminate the harmful effects.
2Measurement precision
If prior art fault localization algorithms are used assuming load is tapped at the end point of the feeder, then fault location estimate is accurate, but this assumption is rarely correct in real medium voltage feeders
Solution Approach 1:
The invention changes the fundamental parameters of the fault location calculation from traditional fundamental frequency impedance measurements to harmonic component ratios. By using the ratio of 2nd harmonic zero-sequence voltage to 3rd harmonic zero-sequence current, the method becomes independent of load configuration assumptions. This allows accurate fault location whether loads are at the beginning, end, or distributed along the feeder, resolving the contradiction between accuracy and adaptability.
3Reliability
If phase-to-earth capacitances in high-impedance earthed systems are present, then the system operates normally, but accuracy of impedance measurement deteriorates
Solution Approach 1:
The invention addresses the capacitance interference problem by changing from fundamental frequency impedance measurements to harmonic component analysis. The use of 2nd harmonic zero-sequence voltage and 3rd harmonic zero-sequence current creates a measurement parameter that is not affected by phase-to-earth capacitances, allowing accurate fault location in high-impedance earthed systems while maintaining system reliability.
Data Source
Figure 1
AI summary
A method and system for determining a location of a phase-to-earth fault in a three-phase electric line (30) of an electric network, the system being configured to monitor current and voltage quantities of the three-phase electric line (30) at a measuring point (40) and calculate a distance (d) between the measuring point (40) and a point of fault (F) using an equation relating the current and voltage quantities to the distance, wherein the system is further configured to calculate load-compensated zero and negative sequence currents, calculate a load-compensated phase voltage of the faulted phase by using the compensated zero sequence current; and use the compensated negative sequence current and the compensated phase voltage for calculating the distance (d) between the measuring point (40) and a point of fault (F).