Power Line Fault Detection Using Parallel Low-Pass Reach Filtering
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Solution Overview
Problem
The existing time domain distance protection schemes for power line faults lack efficiency and accuracy in detecting faults within the protected zone, particularly in distinguishing between internal and external faults.
Innovation Solution
A method and device utilizing parallel processing branches with different low-pass filters having distinct cut-off frequencies to process voltage and current measurements, followed by reach calculations and threshold comparisons to determine faults within the protected zone, incorporating phase selection schemes to identify fault types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single low-pass filter is used in time domain distance protection, then the processing is simple, but the fault detection accuracy and reliability are insufficient
Solution Approach 1:
The protection scheme is divided into multiple parallel processing branches, each with its own low-pass filter having different cut-off frequencies. This segmentation allows simultaneous processing of signals at different frequency levels, improving fault detection reliability by capturing both high-frequency transient components and low-frequency steady-state components without requiring a single complex filter design.
Solution Approach 2:
Different low-pass filters in the parallel branches are configured with different cut-off frequency parameters. By changing this key parameter across multiple branches, the system can detect faults across a broader frequency spectrum, resolving the contradiction between simple processing and reliable detection.
2Measurement precision
If parallel processing branches with different cut-off frequencies are used, then fault detection accuracy improves, but the processing complexity increases
Solution Approach 1:
The measurement and processing functions are segmented into parallel branches, each handling specific frequency ranges. This segmentation improves measurement precision for fault location by analyzing signals at multiple frequency levels simultaneously, while the parallel structure keeps each individual branch relatively simple.
Solution Approach 2:
Each parallel processing branch serves multiple functions: filtering specific frequency components, detecting faults in particular zones, and providing redundant verification. This multi-functionality justifies the parallel structure by demonstrating that each added branch contributes multiple benefits beyond simple complexity increase.
3Reliability
If multiple thresholds are used in parallel branches, then fault detection reliability improves, but the calculation complexity increases
Solution Approach 1:
Multiple thresholds are pre-calculated and set for each parallel branch based on system parameters and expected fault conditions. This preliminary action allows the protection scheme to immediately compare measured values against pre-established criteria during fault events, maintaining high processing speed while improving reliability through multiple comparison points.
Solution Approach 2:
The system uses multiple thresholds in parallel branches, which represents an excessive approach compared to a single threshold. However, this excessive action is justified because it provides redundant verification and reduces false operations, with the overall processing speed maintained through efficient parallel evaluation rather than sequential checks.
Data Source
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AI summary
A method of determining a fault in a protected zone of a power line comprises obtaining (20) measurements at a measurement point at one end of the power line, processing the measurements in a number of parallel processing branches comprising at least two parallel processing branches, wherein the processing in each branch comprises filtering (22, 24, 26) the measurements in a corresponding low pass filter (LPF1, LPF2, LPFN) for obtaining a corresponding set of filtered measurements, wherein the cut-off frequencies (f1, f2, fN) of the low pass filters in these parallel processing branches differ from each other, performing (28, 30, 32) reach calculations on the filtered measurements for obtaining corresponding reach point quantities (QSQ1 QSQ2, QSQN), and comparing (34, 36, 38) the reach point quantities (QSQ1,QSQ2, QSQN) with corresponding thresholds (S1, S2, SN). Finally, it is determined (40) that there is a fault within the protected zone if any threshold is crossed.