Fault Location on Series-Compensated Double-Circuit Lines
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Solution Overview
Problem
Existing fault location methods for power transmission lines, particularly series-compensated double-circuit transmission lines, face inaccuracies due to the use of lumped parameter line models that do not account for distributed parameters, mutual coupling, and shunt capacitances, leading to decreased accuracy as line length increases.
Innovation Solution
A method utilizing the distributed parameter line model to formulate zero, positive, and negative sequence circuits, considering mutual and self impedances and admittances, and calculating synchronization angles from unsynchronized measurements to accurately determine fault locations without requiring source impedances or assuming constant fault resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the lumped parameter line model is used to approximate power networks, then the analysis is simplified, but the fault location accuracy decreases as the line length increases
Solution Approach 1:
The patent transitions from a lumped parameter model to a distributed parameter model, fundamentally changing the mathematical representation of the transmission line. This allows the model to accurately represent long lines where parameters are distributed along the entire length rather than concentrated at discrete points, thereby maintaining accuracy for lines of any length.
Solution Approach 2:
The patent divides the transmission line into infinitesimal segments along its length, treating each segment as a distributed element. This segmentation approach allows the model to capture the continuous distribution of impedance, admittance, and other parameters throughout the line, improving accuracy for long-distance transmission.
2Device complexity
If mutual coupling between parallel lines and shunt capacitance effects are ignored, then the calculation is simplified, but the fault location accuracy deteriorates for long transmission lines
Solution Approach 1:
The patent extracts and explicitly models previously neglected factors such as mutual coupling between parallel lines and shunt capacitance effects. By separating these effects into distinct terms in the distributed parameter equations, the model captures their influence on fault location without overly complicating the overall calculation framework.
Solution Approach 2:
The patent creates a composite mathematical model that integrates multiple physical phenomena (series impedance, shunt admittance, mutual coupling, and capacitance effects) into a unified distributed parameter framework. This composite approach allows all relevant factors to work together synergistically to improve accuracy.
3Ease of operation
If source impedances at terminal substations are assumed constant, then the method is easier to implement, but accuracy is adversely impacted by varying source impedance
Solution Approach 1:
The patent transitions from assuming constant source impedances to modeling source impedance as a dynamic, frequency-dependent parameter. The distributed parameter model incorporates the actual varying characteristics of source impedance through the frequency-dependent propagation constant and characteristic impedance, allowing accurate fault location despite impedance variations.
4Measurement precision
If synchronized measurements are required at both terminals, then fault location accuracy is improved, but the system requires additional synchronization infrastructure
Solution Approach 1:
The patent introduces a synchronization angle calculation as an intermediary step that bridges unsynchronized measurements from both terminals. By calculating the relative phase difference between terminal measurements and compensating for it in the fault location equations, the method achieves accurate results without requiring expensive synchronized measurement infrastructure.
Data Source
AI summary
A highly accurate fault location method for series-compensated double-circuit transmission lines having series compensation devices and metal oxide varistors (SC&MOV) at first and second terminal ends is provided. Synchronized or unsynchronized current phasors and local voltage phasors are used as input to the fault location method. The voltages and currents at the fault point are formulated as a function of the unknown fault location. Boundary conditions for the particular IED-determined fault type are used to derive the fault location formulas.