Wind Turbine Generator Grounding Paths for Stray Current Control
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Solution Overview
Problem
Existing wind turbine protection systems for electrical generators often lead to circling stray currents, causing bearing corrosion and reducing the service life of the generator due to ineffective grounding methods.
Innovation Solution
A protection system with a direct current path from the non-drive end of the generator shaft to ground potential and an alternating current path with an impedance circuit, specifically using capacitors to direct high-frequency stray currents to ground while preventing DC stray currents from following undesired paths, thereby avoiding bearing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If grounding methods are used to avoid stray currents, then bearing corrosion is prevented, but circling stray currents occur within the generator
Solution Approach 1:
The grounding system is segmented into two separate paths: a direct current path connected to the non-drive end of the generator shaft, and an alternating current path with impedance circuit connected to the drive end. This segmentation allows different types of stray currents to be directed through appropriate paths, preventing circling currents while maintaining bearing protection.
Solution Approach 2:
Different grounding characteristics are applied at different locations: the non-drive end receives direct grounding suitable for DC currents, while the drive end receives impedance-based grounding suitable for high-frequency AC currents. This local differentiation optimizes the protection effect for each type of stray current.
2Productivity
If frequency converter is used to convert variable frequency electricity to fixed frequency, then electricity can be supplied to the electric utility grid, but stray currents are introduced to the electric generator
Solution Approach 1:
The protection system acts as an intermediary between the frequency converter and the generator shaft. By providing dedicated stray current paths at both ends of the shaft, the system mediates the harmful effects of frequency converter-induced stray currents while preserving the electricity conversion function.
3Object-affected harmful factors
If insulation in bearings is used to avoid bearing currents, then bearing corrosion is reduced, but voltage buildup occurs in the generator shaft
Solution Approach 1:
Instead of relying solely on bearing insulation, the invention extracts the stray current protection function by providing separate grounding paths at both ends of the shaft. This removes the burden from the bearing insulation and provides active control over voltage and current paths.
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
Effectively controls stray currents, preventing circling currents and bearing corrosion, while ensuring electromagnetic compatibility and reducing noise interference in wind turbines.
Implementation Method 1
said alternating current path comprises an impedance circuit such as at least one capacitor
Implementation Method 2
said at least one capacitor is a type of capacitor with a high rate of voltage change dV/dt capability
Data Source
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AI summary
The invention relates to a protection system (28) for an electric generator (9) of a wind turbine (1) comprising at least one current path (27) from the non drive end (29) of the generator shaft (8) to a ground potential (22), and at least one alternating current path (20) from the drive end (30) of the generator shaft (8) to the ground potential. The invention also relates to a wind turbine and use hereof.