Transmission Line Fault Detection Using Composite Sequence Power
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Solution Overview
Problem
Existing power transmission systems face challenges in detecting faults along transmission lines, particularly high-impedance faults and unsynchronized measurements, which can lead to delayed or inaccurate fault detection.
Innovation Solution
The method involves determining positive, negative, and zero sequence powers and using a composite sequence power calculation to detect faults, relaxing synchronization requirements and enabling directional comparison without needing line impedance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current or impedance measurements are used for fault detection, then fault position identification is enabled, but very high time synchronization demands are required between devices at different ends
Solution Approach 1:
The patent replaces traditional current and impedance measurements with sequence power measurements (positive, negative, and zero sequence powers). This substitution fundamentally changes the measurement basis from electrical current/impedance to power flow characteristics, thereby eliminating the need for high-precision time synchronization between devices while maintaining accurate fault position identification capability
Solution Approach 2:
The patent transforms the measurement parameters from current and impedance to sequence powers. By calculating positive sequence power (S1), negative sequence power (S2), and zero sequence power (S0) at each end of the transmission line, the system achieves fault detection without requiring stringent time synchronization, as power measurements are less sensitive to timing differences compared to current measurements
2Reliability
If impedance measurements are used, then fault detection is enabled, but shortcomings occur regarding high-impedance faults, semaphore effect, and impedance measurement for healthy phases
Solution Approach 1:
The patent segments the power measurement into three distinct sequence components: positive sequence power (S1), negative sequence power (S2), and zero sequence power (S0). Each sequence power provides specific fault information, and their combination through the composite sequence power criterion enables reliable detection of various fault types including high-impedance faults and those with semaphore effects, overcoming the limitations of single-parameter impedance measurements
Solution Approach 2:
The patent creates a composite measurement approach by combining multiple sequence power measurements (S1, S2, S0) into a unified composite sequence power criterion. This composite criterion integrates information from all three sequence components, providing robust fault detection capability that adapts to various fault conditions including high-impedance faults and semaphore effects, thereby enhancing both reliability and versatility
3Loss of time
If sequence power measurements are used, then synchronization requirements are relaxed, but new measurement and calculation methods are required
Solution Approach 1:
The patent develops a universal measurement and calculation framework that computes positive sequence power (S1), negative sequence power (S2), and zero sequence power (S0) using standard phasor measurements already available in power systems. The composite sequence power criterion serves multiple functions: fault detection, fault position identification, and directional determination, all within a single unified methodology that leverages existing measurement infrastructure
Data Source
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AI summary
A method of detecting a fault in a protected line constituting at least a portion of a transmission line in a power transmission system, the transmission line having at least one phase. The method comprises: - determining a positive sequence power, a negative sequence power and a zero sequence power for a positive sequence, a negative sequence and a zero sequence, respectively, of the power in the protected line, determining whether a criterion is fulfilled, wherein the criterion is based on at least one of a composite sequence power determined on basis of the positive sequence power, the negative sequence power and the zero sequence power; and at least one expression determined on basis of at least two of the positive sequence power, the negative sequence power and the zero sequence power, and - if it is determined that the criterion is fulfilled, then determining that a fault has been detected on the protected line.