Fault Location in Ungrounded Power Distribution Systems
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Solution Overview
Problem
Existing methods for locating single-phase-to-ground faults in ungrounded power distribution systems are inefficient, requiring multiple measurements and being suboptimal for complex topologies, and do not accurately determine the exact fault location, leading to potential damage from over-voltages.
Innovation Solution
The method decomposes the fault location process into sequential sub-tasks, using limited measurements at feeder breakers and switches to determine the faulty phase, feeder, section, and line segment, and calculates the exact fault location based on phase-to-ground voltage changes and impedance proportionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple measurements are used to determine fault location, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the fault location determination process into hierarchical levels: first identifying the faulty feeder using zero-sequence power at the substation, then identifying the faulty section using measurements at sectionalizing switches, and finally determining the exact fault location within the segment. This segmentation allows accurate fault location using measurements only at critical points rather than continuous measurements throughout the system.
Solution Approach 2:
The patent introduces zero-sequence power as an intermediary parameter that bridges the relationship between voltage and current measurements. By calculating zero-sequence power (P0 = V0 × I0) at strategic measurement points, the system can determine fault location without requiring direct continuous measurement of all voltage and current parameters along the entire distribution line.
2Reliability
If comprehensive measurements are taken throughout the system, then fault detection reliability is improved, but loss of energy increases
Solution Approach 1:
The patent extracts only the essential measurements needed for fault location: zero-sequence voltage and zero-sequence current at the substation and at sectionalizing switches. By taking out only these critical measurements rather than comprehensive measurements of all phases and all locations, the system maintains high fault detection reliability while minimizing energy consumption for measurement and data processing.
3Productivity
If detailed fault location is determined, then productivity of fault repair is improved, but difficulty of detecting and measuring increases
Solution Approach 1:
The patent applies local quality by placing measurement requirements only at specific locations with strategic value: the substation and sectionalizing switches. These are the only locations where zero-sequence voltage and current measurements are required. The detailed fault location information is then derived computationally from these localized measurements, avoiding the need for complex measurement systems throughout the entire distribution network.
Data Source
AI summary
A method determines a location of a single-phase-to-ground fault in an ungrounded power distribution system. The method detects the faulty phase of the distribution system having the fault and compares a difference between an angle of a voltage and an angle of a current measured at a root of a faulty feeder and boundaries of each section of the faulty feeder to determine a faulty section of a faulty feeder having the fault. A line segment of the faulty section is tested for a change of a sign of a voltage on the faulty phase in the faulty section to determine a faulty line segment. The location of the fault is determined based on a distance from a terminal bus of the faulty line segment to a location along the faulty line segment having a value the voltage on the faulty phase equals zero.