Wave Speed Estimation for Fault Location in Series-Compensated Lines
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Solution Overview
Problem
Existing methods for fault location in series compensated power transmission lines are unreliable due to non-linear characteristics of series capacitors, requiring iterative processes and multiple data sets, and are not feasible in intelligent electronic devices (IEDs, especially when second arrival times are unavailable.
Innovation Solution
A setting-free method for fault location in series compensated lines using end voltage and current measurements, series capacitor value, and pre-fault data to estimate line parameters and wave speed without iterative processes, allowing accurate fault location using first traveling wave arrival times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
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 electrical phasor measurements that are affected by non-linear MOV characteristics, the invention utilizes traveling wave signals that propagate along the transmission line. This substitution allows accurate fault location by measuring the arrival time of traveling waves at the line terminals, bypassing the non-linear measurement issues entirely.
2Measurement precision
If iterative parameter estimation methods are used for series compensated lines, then parameter accuracy may be improved, but the complexity of implementation in IEDs increases
Solution Approach 1:
The patent employs a self-service approach where the traveling wave measurements at the line terminals directly provide the necessary information for fault location without requiring external iterative parameter estimation. The method uses the natural propagation characteristics of traveling waves and the measured arrival times to directly calculate fault location, eliminating the need for complex iterative algorithms and external data sets.
3Reliability
If distributed traveling wave-based fault location technique is used, then wave speed settings are eliminated, but the cost increases due to requiring measurement devices at three locations
Solution Approach 1:
The patent extracts the essential functionality from the distributed three-location measurement technique by using only two terminal measurements. Instead of requiring measurement devices at three locations, the invention extracts the necessary fault location information from traveling wave arrivals at just the two line terminals, combined with pre-fault data from one end, thereby reducing hardware requirements while maintaining the advantage of not needing wave speed settings.
4Adaptability or versatility
If search-based fault location method is used, then wave speed limitations are avoided, but the accuracy deteriorates for faults close to line terminals
Solution Approach 1:
The patent applies preliminary action by using pre-fault data collected at one line terminal before the fault occurs. This pre-captured data includes voltage and current measurements that establish the normal operating conditions and wave propagation characteristics. When a fault occurs, this pre-established information is combined with the fault transient measurements to accurately determine fault location, even for faults near terminals where reflection waves may be weak.
Data Source
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AI summary
The present disclosure relates to a method for obtaining a wave speed or propagation velocity in a power grid comprising a transmission line connected between two buses comprising determining a voltage and current at at least one bus, determining a propagation constant and a characteristic impedance using the voltage, the current and a series compensator capacitance, determining line parameters based on the propagation constant and the characteristic impedance and determining a wave speed or propagation velocity based on the line parameters. The disclosure also relates to a corresponding storage medium, device and power grid.