Fault Direction Determination Using Phase Offset Adjustment
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Solution Overview
Problem
Existing fault detection methods in electrical power systems are unreliable when the system is in motion or experiencing frequency changes, as the pre-fault voltage becomes an unreliable reference, making it difficult to accurately determine the direction of faults.
Innovation Solution
A method that involves measuring and storing the phase of the voltage before a fault, calculating a phase offset after the fault, and adjusting the voltage phase using this offset to ensure accurate fault direction determination, even during system oscillations or frequency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pre-stored voltage is used as reference voltage to determine fault direction, then the method is simple to implement, but the determination becomes unreliable when the power system swings or frequency changes
Solution Approach 1:
The patent stores the phase of the voltage before fault occurrence as a reference, and then calculates a phase offset after the fault to adjust the measured voltage phase. This preliminary storage of phase information allows the system to maintain reliable fault direction determination even when the power system swings or frequency changes, resolving the contradiction between simplicity and reliability.
2Reliability
If the reference voltage is updated after fault detection, then the determination remains accurate during system motion, but additional processing steps are required
Solution Approach 1:
The patent changes the parameter being monitored from absolute voltage phase to phase offset relative to the pre-stored reference phase. By calculating the difference between the pre-fault stored phase and the post-fault measured phase, the method maintains accuracy during system motion while adding only one computational step (phase difference calculation), thus balancing reliability improvement with acceptable complexity increase.
Data Source
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AI summary
The invention concerns a method and computer program product for determining the direction of fault in an electrical power system as well as to a fault handling device. In the fault handling device the voltage at a measurement node of the power system is measured, the phase (FPF) of this voltage (VPF) before a fault is stored, the phase (FF) of this voltage (VF) at the end of a time interval (TI) following directly after a detected fault is determined, a phase offset (FO) is determined as the difference between the phase (FPF) of the measured voltage (VPF) before the fault and the phase (FF) of the measured voltage (VF) at the end of the time interval (TI) and the phase (FF) of the measured voltage (VF) after the detection of the fault is adjusted with the phase offset (FO). Thereafter the adjusted measured voltage is used in determining the direction of fault in relation to the measurement node.