Synchronous Band Pass Filter for High-Impedance Fault Detection
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Solution Overview
Problem
Conventional fault detection systems in poly-phase power systems fail to accurately and quickly identify high-impedance faults, such as arc faults, which can cause significant damage due to their inability to detect current levels similar to or less than normal load current, leading to delayed reaction times and increased risk of component vaporization and fire.
Innovation Solution
A method and apparatus utilizing phase voltages and an imbalance reference value as inputs to a synchronous band pass filter with finite gain to detect faults, avoiding erroneous tripping and enabling rapid fault detection by amplifying predefined harmonic frequency components like first and second harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current sensors are used to detect faults, then low-impedance faults can be detected, but high-impedance faults cannot be detected because they do not cause sufficient current increase
Solution Approach 1:
The patent changes the detection parameter from current magnitude to current waveform characteristics (harmonics, zero-crossing behavior, spike patterns). By analyzing the shape and frequency content of the current waveform rather than just its amplitude, the system can detect both low-impedance faults (which cause large current increases) and high-impedance faults (which cause subtle waveform distortions), thereby resolving the contradiction between reliability and adaptability across different fault types.
2Reliability
If conventional time-over-current protection devices are used, then system protection is provided, but the response time is too slow (seconds to minutes) to effectively protect system components from arc faults
Solution Approach 1:
The patent performs preliminary analysis of current waveform characteristics continuously during normal operation, preparing fault detection algorithms to identify arc fault patterns before they cause damage. By continuously monitoring harmonic content, zero-crossing behavior, and spike patterns, the system can detect arc faults within milliseconds rather than seconds or minutes, enabling rapid response that prevents component vaporization and fire while maintaining system protection.
3Speed
If arc fault detection schemes with 20-50 millisecond detection range are implemented, then rapid fault detection is achieved, but the system may generate erroneous tripping under normal load characteristics
Solution Approach 1:
The patent employs feedback mechanisms where the detected waveform characteristics are continuously compared against learned normal operating patterns. The system adapts to the specific electrical characteristics of the installation and only triggers protection when arc fault patterns (distinctive harmonic signatures, zero-crossing anomalies, spike patterns) are identified that differ from normal load variations. This feedback-based discrimination enables rapid 20-50 millisecond detection while minimizing false trips by distinguishing actual arc faults from benign load fluctuations.
4Reliability
If optical and pressure sensors are used to detect arc faults, then high-impedance faults can be detected, but the system complexity increases considerably making it unsuitable for airborne applications
Solution Approach 1:
The patent extracts the arc fault detection capability from complex multi-sensor systems and implements it using only existing electrical current sensors. By analyzing the electrical waveform characteristics (harmonics, zero-crossing behavior, spike patterns) that are inherently present in arc faults, the system achieves reliable arc fault detection without adding optical or pressure sensors. This extraction approach maintains detection accuracy while dramatically reducing system complexity, making the solution suitable for airborne applications where weight and complexity are critical constraints.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate and swift detection of high-impedance faults, including arc faults, reducing damage by providing a trip signal within a safe time frame of 100 milliseconds, thus minimizing localized damage and preventing catastrophic failures.
Implementation Method 1
filtering the representation of the rectified waveform through a finite gain synchronous band pass filter to generate a synchronous band pass filter output waveform that indicates a magnitude of a predefined harmonic frequency component
Data Source
AI summary
A method and apparatus are provided for detecting a fault condition on a power system. By rectifying power system phase voltages to produce a rectified waveform, and filtering the rectified waveform or a representation of the rectified waveform through a finite gain synchronous band pass filter to generate a synchronous band pass filter output waveform that indicates the magnitude of a predefined harmonic frequency component, a fault condition on a power system can be identified.