Fault Section Identification in Mixed Power Transmission Lines
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Solution Overview
Problem
Power transmission lines with mixed sections (overhead lines and underground cables) face challenges in identifying fault locations due to different surge impedances, making it difficult to determine whether auto-reclosing is necessary.
Innovation Solution
A method and device that compute positive sequence voltages and currents at multiple terminals, calculate junction voltages and currents, and use a ratio of junction voltage to current parameters to accurately identify the faulty section, enabling informed decisions on auto-reclosing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fault detection methods are used in mixed power transmission lines, then the detection process is simple, but the accuracy of fault section identification deteriorates due to different surge impedances between overhead lines and underground cables
Solution Approach 1:
The method segments the power transmission line into distinct sections (overhead line sections and underground cable sections) with known junction points. By dividing the line into segments with different surge impedance characteristics, the system can identify which segment contains the fault by analyzing the propagation behavior of injected test signals across segment boundaries.
Solution Approach 2:
The method introduces test signal injection points and measurement points as intermediary elements between the fault and the detection system. These intermediaries allow indirect observation of fault characteristics by measuring reflected and transmitted test signals, enabling accurate fault section identification without direct access to the fault location.
2Productivity
If auto-reclosing is performed without accurate fault section identification, then power restoration is fast, but underground cables may be damaged due to non-transient faults
Solution Approach 1:
The method performs preliminary fault section identification by injecting test signals and analyzing reflections before the auto-reclosing decision is made. This preliminary action determines whether the fault is in an overhead line section (transient, safe for reclosing) or an underground cable section (non-transient, dangerous for reclosing), enabling informed reclosing decisions that protect cables while restoring power quickly.
Solution Approach 2:
The system uses feedback from test signal measurements to determine fault section location. By continuously monitoring reflected signal characteristics and comparing them against known surge impedance values for different line sections, the system provides feedback that guides the auto-reclosing decision-making process, ensuring cables are protected from damaging reclosing operations.
3Measurement precision
If the surge impedance difference between overhead lines and underground cables is considered in fault detection, then fault section identification accuracy improves, but the detection and measurement difficulty increases
Solution Approach 1:
The method changes the operational parameters by injecting test signals at specific frequencies and measuring reflected signal characteristics. By varying the test signal parameters and analyzing how reflections change with different line section configurations, the system exploits the surge impedance differences between overhead and underground sections to accurately identify fault locations without requiring complex measurement equipment.
Data Source
AI summary
Techniques for identifying faulty sections in power transmission lines are described. A first positive sequence voltage and first positive sequence current at a first terminal of a power transmission line are computed based on a first voltage and first current at the first terminal. A second positive sequence voltage and second positive sequence current at a second terminal are computed based on a second voltage and second current. Based on the first positive sequence voltage and the first positive sequence current, a first junction voltage and first junction current from the first terminal at a junction are computed. Based on the second positive sequence voltage and the second positive sequence current, a second junction voltage and second junction current from the second terminal are computed. A ratio of a junction voltage parameter to a junction current parameter is computed. Using the ratio, the faulty section is identified.