Stator Winding Fault Detection Using Neutral-Point Current Imbalance
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Solution Overview
Problem
Existing methods for detecting electrical faults in stator windings of electric machines, such as those in wind turbines, often lead to high currents and potential damage or fire hazards, and lack sensitivity and localization capabilities.
Innovation Solution
A method involving measuring currents between subgroups of windings and neutral points to detect impedance changes caused by faults, allowing for fault detection without load and improved localization by analyzing circular currents, which can be done during the spin-up of a wind turbine before connecting to a load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fault detection methods are used to detect turn faults, then fault detection capability is provided, but high currents are generated leading to strong local heating and fire hazards
Solution Approach 1:
The patent performs fault detection during the spin-up phase before the generator is connected to a load and before high currents are generated. By conducting the measurement in advance during a no-load or low-load period, the system can detect turn faults before they cause dangerous heating or fire hazards.
Solution Approach 2:
The patent replaces conventional electrical measurement methods that require load operation with a method based on measuring voltage imbalances during spin-up. This substitution allows fault detection without requiring the generator to be under electrical load, thereby avoiding the generation of high currents and associated heating risks.
2Reliability
If vibration measurement is used to detect turn faults, then fault detection is possible, but sensitivity is low due to small torque ripple in large machines
Solution Approach 1:
The patent replaces vibration-based detection with an electrical measurement method that monitors voltage imbalances during the spin-up phase. This electrical measurement approach is far more sensitive than vibration measurement because it directly detects the electrical asymmetry caused by turn faults before mechanical effects manifest.
Solution Approach 2:
The patent performs voltage imbalance measurements during the spin-up phase before the generator is connected to a load. This preliminary action allows detection of turn faults with high sensitivity by measuring electrical parameters when the system is still in a controlled, low-power state.
3Reliability
If vibration measurement is used to detect turn faults, then fault detection is possible, but fault localization is not possible
Solution Approach 1:
The patent divides the stator windings into multiple groups and measures voltage imbalances for each group separately during spin-up. By analyzing which specific group exhibits the voltage imbalance, the system can localize the fault to a particular winding group or phase, providing valuable diagnostic information for maintenance.
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 reduces the risk of damage and fire hazards while enhancing sensitivity and localization of faults, enabling early detection and prevention of further damage.
Implementation Method 1
electrical faults in a stator change the impedance of a winding that comprises such a fault. This is especially true for turn-to-turn faults that create a short between adjacent turns of a winding
Implementation Method 2
a change of the impedance of one of the windings shifts the potential on the side of that winding that is connected to the phase connection for the respective group. 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
AI summary
A method for detecting an electrical fault in the stator of an electric machine is provided, wherein the stator includes multiple groups of windings, wherein the windings of each group are assigned to a respective phase of the electric machine, including the steps of: determining a respective current firstly between a subgroup of one of the groups of windings and a distinct further subgroup of the same group of windings and/or secondly between a subgroup of one of the groups of windings and a neutral point, and/or thirdly between a neutral point and either a further neutral point or to a common neutral point connected to at least the neutral point and the further neutral point, evaluating a fault condition, wherein the fulfilment of the fault condition depends on the respective determined current, and outputting a fault signal to personal and/or a device when the fault condition is fulfilled.