Stator Winding Fault Detection Using Circular Current Measurement
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Solution Overview
Problem
Existing methods for detecting electrical faults in stators of electric machines, such as generators in wind turbines, are inadequate in sensitivity and risk causing further damage due to high currents and potential fires, and lack effective fault localization.
Innovation Solution
Measure circular currents between windings connected to a neutral point or separate neutral points to detect impedance changes caused by faults, allowing fault detection and localization without a load, using current sensors and processing units to identify fault conditions based on measured currents and torque oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical imbalance detection is performed using negative sequence voltage while the generator drives a load, then turn faults can be detected, but high currents cause strong local heating and fire hazards
Solution Approach 1:
The patent measures circular currents during the spin-up phase before the generator is connected to the external load. This preliminary measurement allows fault detection to occur before high load currents are applied, preventing the harmful heating effects that would occur if detection were performed under load conditions.
Solution Approach 2:
The patent uses circular currents as an intermediary measurement parameter instead of directly measuring the harmful load currents. By measuring the circular currents that flow through the stator windings during spin-up, the system can detect faults without exposing the machine to the high currents that cause heating and fire hazards.
2Reliability
If vibration measurement is used to detect torque ripple caused by turn faults, then fault detection is possible, but the sensitivity is relatively low due to small torque ripple in large machines
Solution Approach 1:
The patent replaces the mechanical vibration measurement approach with an electrical measurement approach. Instead of measuring mechanical vibrations caused by torque ripple, the system measures electrical circular currents directly in the stator windings, providing a more sensitive and direct indication of turn faults.
Solution Approach 2:
The patent changes the measurement parameter from mechanical vibration to electrical current. By measuring the circular currents that flow through faulty windings, the system achieves higher measurement precision and sensitivity compared to mechanical vibration measurement, especially in large machines where torque ripple is small.
3Reliability
If vibration measurement is used to detect turn faults, then fault detection is possible, but fault localization among multiple windings is not possible
Solution Approach 1:
The patent segments the stator windings into multiple groups and measures circular currents for each group separately. This segmentation allows the system to identify which specific group or winding contains the fault by comparing the circular current measurements across different segments, thereby achieving fault localization.
Solution Approach 2:
The patent uses feedback from multiple circular current measurements taken from different stator winding groups to determine the location of the fault. By analyzing the pattern of circular currents across segmented groups, the system can identify which specific winding or group is faulty, providing localization information that was missing from vibration-based methods.
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
Enables early detection of electrical faults with reduced risk of damage, allowing for timely shutdown or operational adjustments, and facilitates precise fault localization in stator windings.
Implementation Method 1
electrical faults in a stator change the impedance of a winding that comprises such a fault
Implementation Method 2
This leads to a potential difference between points of the circuit that would otherwise be on the same potential and therefore lead to circular currents within the stator windings
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
Method for detecting an electrical fault in the stator (4) of an electric machine (2), wherein the stator (4) comprises multiple groups (38, 51, 52) of windings (19 - 27, 69 - 77), wherein the windings (19 - 27, 69 - 77) of each group (38, 51, 52) are assigned to a respective phase (28, 29, 30) of the electric machine (29), comprising the steps of: - determining a respective current (42, 43, 44) • firstly between a subgroup (64, 65, 66) of one of the groups (38, 51, 52) of windings (19 - 27, 69 - 77) and a distinct further subgroup (39, 53, 54) of the same group (38, 51, 52) of windings (19 - 27, 69 - 77) and/or • secondly between a subgroup (64, 65, 66) of one of the groups (38, 51, 52) of windings (19 - 27, 69 - 77) and a neutral point (35, 36, 37), and/or • thirdly between a neutral point (35, 36, 37) and either a further neutral point (35, 36, 37) or to a common neutral point connected to at least the neutral point and the further neutral point, - evaluating a fault condition (63), wherein the fulfilment of the fault condition (63) depends on the respective determined current (42, 43, 44), and - outputting a fault signal (83) to personal and/or a device (15) when the fault condition (63) is fulfilled.