Fault Wave Arrival Determination Using Voltage Derivative
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Solution Overview
Problem
Existing methods for determining the time of arrival of a fault wave in power transmission systems, particularly in DC lines, face accuracy issues due to varying wave amplitudes and shapes, and are influenced by operating conditions and noise levels, leading to imprecise fault location.
Innovation Solution
A method and apparatus that utilize a power quantity scaling unit with a Rogowski coil and operational amplifier to measure and analyze the derivative of the line voltage, setting a threshold based on significant swing amplitude to detect the starting point of the fault wave, allowing precise determination of the time of arrival using general-purpose satellite synchronized clocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wavelet transform and current detail signals are used for fault location, then AC power line fault detection works well, but DC power line fault detection is less suitable
Solution Approach 1:
The patent changes the measurement parameter from current detail signals (wavelet transform) to the derivative of voltage with respect to time (dV/dt). This parameter change enables the fault detection method to be effectively applied to DC power lines while maintaining high measurement precision for fault location.
2Ease of operation
If fault wave arrival time is determined using conventional threshold methods, then simple implementation is achieved, but accuracy deteriorates due to varying wave amplitudes and noise levels
Solution Approach 1:
The patent implements a dynamic thresholding mechanism where the threshold is not fixed but adapts based on the actual wave characteristics. The threshold is set proportional to the maximum amplitude observed in the signal, allowing the detection method to maintain simplicity while achieving high accuracy despite varying wave amplitudes and noise levels.
3Measurement precision
If specialized satellite synchronized clocks are used for time stamping, then time measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces expensive, complex specialized satellite synchronized clocks with general-purpose clocks that are cheaper and simpler. By implementing a robust signal processing algorithm with adaptive thresholding, the system achieves sufficient time measurement accuracy using ordinary clock components, eliminating the need for specialized time-stamping hardware.
4Area of stationary object
If measurement points are placed far apart to cover long power lines, then coverage area is improved, but fault location precision deteriorates due to larger time difference measurements
Solution Approach 1:
The patent substitutes the mechanical approach of placing measurement points close together with a signal processing approach. By using the derivative of voltage (dV/dt) and implementing precise threshold detection algorithms, the system can accurately determine fault location even when measurement points are far apart, effectively replacing physical proximity requirements with computational precision.
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 approach provides improved accuracy in determining the time of arrival of fault waves, especially for faults close to measurement points, and enables precise distance calculation to faults, even in long DC power lines, while avoiding the need for specialized satellite clocks.
Implementation Method 1
A method and an apparatus for determining the time of arrival of a fault wave... utilize a power quantity scaling unit with a Rogowski coil... to measure and analyze the derivative of the line voltage
Data Source
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AI summary
The present invention relates to a method and apparatus for determining the time of arrival of a fault wave at a measurement point of a power transmission system. The apparatus (20) comprises a measurement unit (32) measuring a power quantity (PQ) of the system at the measurement point (Pl) for obtaining a measurement quantity being a potential fault wave, a time keeping unit (40), a storage unit (38) storing the measurement quantity, a comparing unit (36) comparing the measurement quantity with a threshold (T1) for detecting the presence of a fault wave (W1) and an analyzing unit (42). The analyzing unit analyzes measurements made before the fault wave presence was detected, determines the starting point (SP) of the fault wave based on the analysis and sets the time of the starting point to be the fault wave arrival time (T1).