Synchronous Machine Fault Detection via Field Current and Shaft Voltage Harmonics
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Solution Overview
Problem
Existing methods for detecting fault conditions in synchronous machines, such as stator current and vibration measurements, are inadequate as they require expensive equipment and do not accurately reflect machine conditions, and existing fault detection systems only address stator inter-turn faults, failing to identify multiple or simultaneous fault conditions effectively.
Innovation Solution
A method utilizing field current and shaft voltage indicators to evaluate frequency spectra, where frequency components at specific harmonics indicate different fault conditions, allowing for simultaneous and multiple fault detection and identification by synergistically analyzing field current and shaft voltage frequency spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stator current measurements are performed under high voltage conditions, then fault detection capability is improved, but expensive sensor equipment is required
Solution Approach 1:
The patent introduces shaft voltage as an intermediary parameter that indirectly reflects stator fault conditions. Instead of directly measuring stator current under high voltage, the system measures shaft voltage (which is electrically connected to the stator through the rotor) and analyzes its harmonic content. This intermediary measurement approach enables fault detection without requiring expensive high-voltage tolerant sensors.
2Device complexity
If vibration measurements are used for fault detection, then the monitoring system is simple, but vibration levels do not reflect synchronous machine conditions satisfactorily
Solution Approach 1:
The patent replaces mechanical vibration measurements with electrical shaft voltage measurements. Both are relatively simple to implement, but electrical measurements provide superior sensitivity to internal electrical faults such as stator inter-turn short circuits. The shaft voltage signal contains harmonic components that directly correlate with specific fault types, offering better diagnostic precision while maintaining system simplicity.
3Device complexity
If only field current measurements are used, then the monitoring system is simple, but multiple and simultaneous fault conditions cannot be identified
Solution Approach 1:
The patent merges field current measurements with shaft voltage measurements to create a comprehensive fault diagnosis system. By combining these two measurement approaches and analyzing their respective harmonic content together, the system can identify multiple simultaneous fault conditions. The synergistic analysis of both signals provides enhanced adaptability and versatility in fault detection while keeping individual measurement systems relatively simple.
Data Source
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AI summary
The present disclosure relates to a method of determining a fault condition in a synchronous machine. The method comprises a) obtaining a field current signal and a shaft voltage signal of the synchronous machine, b) transforming the field current signal and the shaft voltage signal to obtain a field current frequency spectrum and a shaft voltage frequency spectrum, and c) determining whether a fault condition is present, and in case a fault condition is present identifying a type of the fault condition, based on harmonic content of the field current frequency spectrum and harmonic content of the shaft voltage frequency spectrum.