Stator Winding Insulation Testing Using Terahertz Defect Localization
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Solution Overview
Problem
Current methods for detecting ageing phenomena in stator winding insulation of electric machines, such as generators, are inadequate for identifying defects in regions with insufficient electric field strength and lack spatial accuracy, leading to incomplete detection and potential irreversible damage.
Innovation Solution
Employ terahertz measurement technology for non-destructive testing of accessible insulation regions using a terahertz sensor moved by an electromechanical displacement unit, allowing for accurate detection and localization of defects through electromagnetic waves with low photon energy and short wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If partial-discharge measurement is used to detect ageing phenomena in stator winding insulation, then detection capability is improved for regions with strong electric field, but measurement precision and detection completeness deteriorate due to inability to detect defects in regions with insufficient electric field strength
Solution Approach 1:
The patent replaces the electric field-based partial-discharge measurement method with a terahertz electromagnetic wave-based measurement method. The terahertz sensor emits terahertz waves that penetrate the insulation material and detect defects through changes in wave propagation characteristics, eliminating the dependency on electric field strength for detection capability. This substitution allows comprehensive detection of ageing phenomena in all insulation regions regardless of electric field intensity.
Solution Approach 2:
The patent changes the fundamental measurement parameter from electric field strength to terahertz wave propagation characteristics (such as attenuation, phase velocity, and reflection). By measuring how terahertz waves interact with the insulation material and defects, the system can detect ageing phenomena based on material property changes rather than electric field intensity, enabling complete detection across all insulation regions.
2Reliability
If partial-discharge measurement is used to locate ageing phenomena, then detection coverage is improved, but localization accuracy deteriorates due to delay time measurement limitation of about 1.2 m
Solution Approach 1:
The patent substitutes the time-based localization method with a spatial resolution-based method using terahertz wave imaging. The short wavelength of terahertz radiation (3 mm to 30 μm) provides inherent spatial resolution that enables precise localization of defects without relying on delay time measurements. The terahertz sensor can resolve defect positions with much higher accuracy than the 1.2 m limitation of partial-discharge measurement.
Solution Approach 2:
The patent transitions from one-dimensional delay time measurement to multi-dimensional spatial imaging using terahertz waves. By capturing the spatial distribution of terahertz wave interactions with defects, the system achieves precise localization in three-dimensional space, providing both accurate position information and detailed imaging of the insulation structure.
3Measurement precision
If high-voltage testing is used to detect ageing phenomena, then detection sensitivity is improved, but safety deteriorates due to risk of breakdown in irreparable damage
Solution Approach 1:
The patent replaces high-voltage electrical testing with non-ionizing terahertz electromagnetic radiation. The terahertz waves interact with the insulation material through dielectric properties and wave propagation characteristics, allowing detection of ageing phenomena without applying high voltages that could cause breakdown. This substitution maintains detection sensitivity while eliminating the harmful effect of potential irreversible damage.
Solution Approach 2:
The patent converts the potential harm of high-voltage testing into a beneficial non-invasive measurement approach. By using terahertz waves with low photon energy, the system achieves detection capability without the dangerous side effects of high-voltage breakdown risk, transforming a hazardous testing method into a safe diagnostic tool.
4Ease of operation
If endoscope or mirror is used to detect surface-level defects in insulation, then ease of operation is improved, but detection depth deteriorates as deeper-lying flaws remain unidentified
Solution Approach 1:
The patent substitutes optical inspection methods (endoscope, mirror) with terahertz electromagnetic wave penetration-based detection. The terahertz waves can penetrate deep into the insulation material and detect defects at various depths by measuring changes in wave propagation. This substitution maintains the ease of operation with automated sensing while dramatically improving detection depth capability.
Solution Approach 2:
The patent transitions from surface-level two-dimensional inspection to three-dimensional deep inspection using terahertz wave penetration. The measurement system can detect defects at different depths by analyzing the attenuation and phase characteristics of terahertz waves, providing volumetric inspection capability rather than limited surface inspection.
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 precise identification and localization of defects in insulation, reducing the risk of unexpected machine failure and enabling timely repairs, while being safe for industrial use and providing data for future insulation design improvements.
Implementation Method 1
Due to low photon energy, terahertz radiation can penetrate non-conductive materials
Implementation Method 2
terahertz measurement technology is based on electromagnetic waves in the frequency range of 0.1 to 10 terahertz
Data Source
AI summary
A method and testing device for the non-destructive testing of at least partial regions of an insulation of a stator winding of an electric machine, in particular a generator of a high-voltage motor, wherein the non-destructive testing is carried out in situ at the installation site of the electric machine using terahertz measurement technology.