Single-Phase-to-Ground Fault Location in Ungrounded Distribution Systems
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Solution Overview
Problem
Current methods for detecting and locating single-phase-to-ground faults in ungrounded power distribution systems are inefficient, particularly due to the need for additional frequency measurements and the difficulty in determining load voltages, which complicates the identification of faulty line segments and locations.
Innovation Solution
The method involves using measurements from feeder breakers and switches with sensors to determine shunt and fault caused residual voltages, comparing these voltages' angles to identify faulty line segments, and determining fault locations based on voltage and current distributions without requiring load information, thus simplifying the process and reducing measurement efforts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional methods using directional elements and zero sequence impedance are used, then fault detection capability is provided, but the method complexity and measurement requirements increase
Solution Approach 1:
The patent extracts and utilizes only the necessary measurement components (residual voltage and residual current) from the complex set of available measurements. By focusing on these two key parameters and their phase angle relationships, the method achieves reliable fault detection without requiring the complex directional elements and zero sequence impedance calculations mentioned in the background.
Solution Approach 2:
Instead of using complex impedance calculations and directional elements to determine fault location, the patent inverts the approach by using simple phase angle comparisons of residual voltage and current. The method determines fault location by comparing the phase angle of residual voltage with the phase angle of residual current, which provides a simpler and more direct approach.
2Measurement precision
If additional frequency measurements are introduced, then measurement precision is improved, but device complexity and measurement efforts increase
Solution Approach 1:
The patent extracts only the essential measurement components needed for fault location: residual voltage and residual current at power frequency. By eliminating the need for additional frequency measurements while focusing on these two key parameters, the method achieves sufficient precision for fault location without increasing device complexity or measurement efforts.
Solution Approach 2:
The patent changes the approach from using multiple frequency measurements to using phase angle relationships at a single power frequency. By transforming the measurement strategy to focus on phase angle comparisons rather than frequency domain analysis, the method maintains measurement precision while reducing the complexity of measurement requirements.
3Measurement precision
If load determination is required to identify faulty line segments, then measurement precision is improved, but device complexity and processing requirements increase
Solution Approach 1:
The patent extracts the fault location determination from the complex process that requires load information. By using only the phase angle relationship between residual voltage and residual current, the method identifies faulty line segments without requiring load determination, thus reducing processing complexity while maintaining identification accuracy.
Solution Approach 2:
Instead of determining fault location by calculating impedances and comparing with load conditions, the patent inverts the approach by using direct phase angle comparisons of residual voltage and current. This inverted approach eliminates the need for load determination and provides a simpler processing method that maintains precision in faulty line segment identification.
Data Source
AI summary
The method determines shunt caused residual voltages and fault caused residual voltages on the upstream bus and the downstream bus of the line segment within a faulty feeder section of a faulty feeder. The line segment is designated as a faulty line segment when a reference angle of a faulty phase is between a first angle of a difference between an angle of the fault caused residual voltage and an angle of the shunt caused residual voltage on the upstream bus and a second angle of a difference between an angle of the fault caused residual voltage and an angle of the shunt caused residual voltage on the downstream bus. The location of the fault is determined at a point on the faulty line segment with a difference between the angles of the fault and the shunt caused residual voltages in phase with the reference angle.