Traveling Wave Fault Location for Transmission Lines Without Calibration
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Solution Overview
Problem
Existing fault location methods for power transmission lines, especially impedance-based methods, face inaccuracies due to dependence on line parameters and mutual coupling, which are difficult to accurately estimate, especially in dynamic conditions, leading to inefficiencies in fault identification and repair.
Innovation Solution
A parameter-free traveling wave-based fault location method that uses synchronized measurements at two terminals to detect and compare arrival times of traveling waves, allowing for accurate identification of the faulty half or midpoint of the line without requiring calibration of propagation velocity or line parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance-based fault location methods are used, then fault location can be determined using fundamental voltages and currents, but accuracy deteriorates due to dependence on line parameters, mutual coupling, and source impedances that are difficult to accurately estimate
Solution Approach 1:
The patent extracts and eliminates the dependency on line parameters (propagation velocity, inductance, capacitance) from the fault location calculation. By using traveling wave arrival time differences between two ends of the line, the method removes the need for accurate line parameter estimation, directly addressing the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent changes the fundamental parameter used for fault location from impedance-based calculations (which require line parameters) to traveling wave arrival time measurements. This parameter change enables accurate fault location without depending on difficult-to-estimate line parameters, mutual coupling, or source impedances
2Speed
If fast protection schemes clear faults in less than two cycles, then system stability is improved, but impedance-based fault location accuracy deteriorates because current does not reach steady state and voltage does not drop to steady-state
Solution Approach 1:
The patent performs fault location measurement at the preliminary stage immediately when traveling waves arrive at the line terminals, before the system reaches steady state. By capturing the transient traveling wave signals and calculating fault location based on arrival time differences, the method enables accurate fault location during fast protection operation (less than two cycles), resolving the contradiction between fault clearing speed and measurement precision
3Measurement precision
If communication based two-end synchronous measurement methods are used, then fault location accuracy is improved, but reliability deteriorates due to high dependence on accurate line propagation velocity which varies with loading, weather, aging, and material properties
Solution Approach 1:
The patent implements a self-calibrating approach where the system automatically determines the effective propagation velocity by comparing traveling wave arrival times at both line terminals. This self-service mechanism eliminates the need for manual calibration and compensates for variations in propagation velocity caused by loading, weather, aging, and material properties, thereby improving both measurement precision and reliability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables precise fault location independent of line parameters, reducing the need for extensive data sets and improving the speed and accuracy of fault detection, thereby enhancing the reliability and efficiency of power transmission line maintenance.
Implementation Method 1
travelling wave based fault location with measurements at two ends of a power transmission line
Data Source
Figure 1(a)~1(b)
Figure 2~3
Figure 4
AI summary
The invention provides a method and device for fault location in a power transmission line. The method comprises obtaining (202) arrival times of first and second peaks of travelling waves detected at a first terminal and a second terminal of the power transmission line. The method also comprises identifying (204, 206) one of a first half, a second half, and a mid-point of the power transmission line, as having the fault, based on a comparison of the arrival times of the travelling wave detected from measurements at the first terminal with the arrival times of the travelling wave detected from measurements at the second terminal. Accordingly, the fault location is estimated (208, 210, 212) with the arrival times of the first and second peaks of the corresponding travelling waves, and the length of the power transmission line.