Series-Compensated Transmission Line Fault Location
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Solution Overview
Problem
Accurate fault location on series-compensated transmission lines is challenging due to the capacitance added by capacitor banks, which disrupts impedance measurements and requires new methods to handle incomplete two-end measurements.
Innovation Solution
A fault location algorithm using subroutines that utilize synchronized three-phase current measurements from both line terminals and one-end three-phase voltage measurements to determine per unit distance to a fault, allowing for accurate fault location even with interrupted data communication between line ends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If capacitor bank is added for series-compensation to transmit power over long distances, then power transfer capability is improved, but fault location accuracy deteriorates due to impedance discontinuity
Solution Approach 1:
The patent divides the series-compensated transmission line into two separate protected zones: one from terminal A to the capacitor bank, and another from terminal B to the capacitor bank. Different fault location algorithms are applied to each zone based on the specific impedance characteristics of that segment, allowing accurate fault location despite the overall impedance discontinuity caused by the capacitor bank.
Solution Approach 2:
The patent applies different fault location algorithms tailored to specific local conditions: one algorithm for faults occurring before the capacitor bank and another algorithm for faults occurring after the capacitor bank. This localized approach ensures that each algorithm operates within its optimal performance range, maintaining high accuracy despite the non-uniform impedance profile of the series-compensated line.
2Loss of information
If two-end current measurements are used for fault location, then measurement completeness is improved, but system complexity increases due to data communication requirements
Solution Approach 1:
The patent designs a fault location system that can operate in multiple modes: full two-end measurement mode for optimal accuracy, and degraded one-end measurement mode when communication is interrupted. The same fault location device at each terminal can function independently using local measurements, providing universal operation across different communication conditions without requiring separate systems.
Solution Approach 2:
The patent prepares for potential communication failures by designing algorithms that can operate with incomplete measurements. The fault location system is pre-configured to handle both complete two-end data and partial one-end data scenarios, cushioning against the harmful effect of communication interruptions and ensuring continuous fault location capability.
3Length of stationary object
If series-compensation is applied to extend transmission distance, then transmission range is improved, but fault detection difficulty increases due to non-linear current dependent circuit
Solution Approach 1:
The patent accounts for the non-linear, current-dependent characteristics of the capacitor bank by using different impedance parameters in the fault location algorithms depending on the operating conditions and fault location. The algorithms dynamically adjust to the changing circuit parameters caused by series-compensation, enabling accurate fault detection despite the complex non-linear behavior.
Data Source
AI summary
The invention relates to a method for locating a fault in a series-compensated two-terminal power transmission line 3 comprising a compensating bank 2 for providing series- compensation to the transmission line. Different subroutines are utilized for locating faults on line segments from the first terminal to the compensating bank and line segments from the second terminal to the compensating bank. A selection is then made in order to determine a valid result. The subroutines utilize three phase currents synchronized measurements from both terminals (A, B) and a three phase voltage measurements from one terminal (A) for determining the respective per unit distance dFA, dFB to a fault (FA, FB). The invention also relates to a transmission line system, a device for fault protection and computer programs.