Exciter Current Spectrum Analysis for Synchronous Machine Fault Detection
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Solution Overview
Problem
Current methods for detecting fault conditions in synchronous machines are complex, require expensive high-voltage sensors, and often fail to accurately identify fault types due to the limitations of stator current and vibration measurements.
Innovation Solution
Measuring the exciter current and transforming it into a frequency spectrum to determine various faults, allowing for the identification of stator and rotor short-circuit faults through dominant frequency components, which can be done using cheaper sensors at a stationary location outside the rotating parts of the machine.
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 sensor cost and safety risks increase
Solution Approach 1:
The patent uses exciter current as an intermediary measurement parameter. Instead of directly measuring stator current under high voltage conditions, the system measures the exciter current which is electrically coupled to the stator winding but operates at lower voltage levels. This intermediary measurement approach maintains fault detection capability while avoiding the need for expensive high-voltage sensors and reducing safety risks.
2Ease of operation
If vibration measurements are used for fault detection, then the system is simple to implement, but measurement precision for synchronous machine conditions is insufficient
Solution Approach 1:
The patent changes the measurement parameter from vibration to exciter current. By measuring the electrical parameter (exciter current) rather than mechanical vibration, the system achieves both ease of implementation and improved measurement precision for synchronous machine conditions. The exciter current directly reflects the electromagnetic state of the machine, providing more accurate fault detection than vibration measurements.
3Measurement precision
If rotor current measurements are performed to detect faults, then fault detection capability is improved, but sensor requirements become more stringent due to high current conditions
Solution Approach 1:
The patent uses exciter current as an intermediary that is electrically coupled to the rotor winding but operates at lower current levels. By measuring the exciter current instead of directly measuring the high-current rotor current, the system maintains fault detection capability while using sensors with less stringent current withstand requirements.
4Measurement precision
If multiple measurement methods are used to identify different fault types, then fault identification accuracy is improved, but system complexity increases
Solution Approach 1:
The patent makes the exciter current measurement system universal for detecting multiple fault types. By analyzing different frequency components and harmonic content of the same exciter current signal, the system can identify stator winding faults, rotor winding faults, and other synchronous machine faults using a single measurement point, thereby avoiding the complexity of multiple separate measurement systems.
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
Simplifies fault condition determination by providing a characteristic signature for different electro-mechanical faults, reducing sensor requirements and improving safety while accurately identifying fault types, including stator and rotor short-circuits and eccentricity faults.
Implementation Method 1
the rotor and stator interact electromagnetically such that rotation of the rotor is obtained in case the synchronous machine is a motor, and such that current is induced in the stator coils in case the synchronous machine is a generator
Data Source
Figure 1a~1c
Figure 2~3
AI summary
The present disclosure relates to a method of determining an electromechanical fault condition in a synchronous machine having a stator a rotor, and an exciter, wherein the exciter is a rotating exciter having an exciter stator, an exciter rotor, and exciter stator windings, wherein the rotating exciter has an AC/AC type of stator-rotor arrangement, wherein the method comprises: a) obtaining an exciter current signal which is a measurement of an exciter current flowing through the exciter stator windings of the exciter, wherein the exciter current signal is an exciter stator current, b) transforming the exciter current signal to obtain an exciter current frequency spectrum, and c) determining that a stator short-circuit fault is present in case the harmonic content of the exciter current frequency spectrum comprises a dominant frequency component at 3fs*(1-2s), where fs is the power supply frequency and s is the rotor slip of the exciter..