Wave Speed Estimation for Fault Location in Series-Compensated Grids
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Solution Overview
Problem
Existing methods for fault location in series compensated power transmission lines face challenges due to non-linear characteristics of series capacitors, requiring complex measurements and calculations, and often fail to provide accurate and reliable solutions.
Innovation Solution
A setting-free fault location method that estimates line parameters and wave speed using end voltage and current measurements, without iterative processes, allowing for accurate fault location without requiring measurements across the series compensator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If phasor-based fault location algorithms are used in series compensated systems, then the measurement process is simplified, but the fault location accuracy deteriorates due to non-linear characteristics of MOV
Solution Approach 1:
The patent replaces phasor-based measurement methods with traveling wave-based methods. Instead of using traditional phasor analysis that assumes linear characteristics, the invention uses traveling wave arrival time detection which is not affected by the non-linear MOV characteristics. This substitution of measurement principle resolves the contradiction by maintaining measurement simplicity while achieving accurate fault location in series compensated systems.
2Measurement precision
If traveling wave-based fault locators with wave speed settings are used, then fault location accuracy is improved to within hundreds of meters, but the method requires accurate line parameters which are difficult to obtain online
Solution Approach 1:
The patent performs preliminary action by using offline or historical data to estimate line parameters and calculate wave speed before actual fault location is needed. This pre-computation of wave speed eliminates the need for real-time parameter estimation during faults, resolving the contradiction by achieving high accuracy without requiring difficult online measurements.
Solution Approach 2:
The patent introduces wave speed as an intermediary parameter that bridges the gap between difficult-to-obtain line parameters and fault location calculation. By using wave speed (which can be determined from travel time measurements) as the intermediate quantity, the system achieves accurate fault location without directly requiring precise knowledge of line parameters during fault conditions.
3Ease of operation
If setting-free traveling wave-based fault locators requiring second arrival time are used, then wave speed settings are eliminated, but the method fails when second arrival time is not available
Solution Approach 1:
The patent uses a backup or alternative measurement approach by relying on first arrival time detection at multiple locations rather than requiring second arrival time. This creates a redundant measurement strategy where fault location can be determined using alternative data sources, ensuring reliability even when second arrival time is unavailable while maintaining the setting-free operation.
4Device complexity
If distributed traveling wave-based fault location using three locations is implemented, then wave speed input is not required, but the cost increases due to additional measurement devices
Solution Approach 1:
The patent makes the measurement devices at the two terminal locations perform multiple functions: they detect both the first and second arrival times of traveling waves, and use these measurements to calculate wave speed and locate faults. This multi-functionality eliminates the need for additional measurement devices while maintaining the setting-free operation, resolving the contradiction by achieving the same result with fewer devices.
Data Source
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AI summary
The present disclosure relates to a method for determining a wave speed or propagation velocity in a power grid comprising a transmission line connected between two buses. The method comprises obtaining a voltage and current at at least one bus, determining a propagation constant using the voltage, the current and a series compensator capacitance and determining a wave speed or propagation velocity based on the propagation constant and a frequency of the transmission line.