Stator Winding Insulation Testing Using Terahertz 3D Defect Imaging
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Solution Overview
Problem
Existing methods for detecting aging phenomena in stator winding insulation of electrical machines, such as generators, are inadequate for complete coverage and localization of defects, particularly in areas with insufficient electric fields, leading to undetected long-term damage.
Innovation Solution
Employing terahertz measurement technology with a terahertz sensor and an electro-mechanical displacement unit, such as an articulated-arm robot, to non-destructively test externally accessible sections of the insulation, generating precise 3D images of insulation defects using frequency-modulated continuous wave radar.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If partial discharge measurements are used to detect aging phenomena in stator winding insulation, then detection capability is improved in areas with sufficient electric field, but detection coverage deteriorates in areas with insufficient electric field (such as bent sections outside stator slots)
Solution Approach 1:
The patent introduces terahertz radiation as an intermediary measurement medium that does not depend on electric field strength. Unlike partial discharge measurements that require sufficient electric field, terahertz waves can penetrate and detect insulation defects in all areas including bent sections outside stator slots, where the electric field is insufficient for conventional methods.
Solution Approach 2:
The patent replaces the electric field-based detection mechanism with electromagnetic radiation (terahertz waves). This substitution allows detection to occur independently of the electric field distribution, enabling comprehensive coverage of all insulation areas including those with insufficient electric field strength.
2Reliability
If partial discharge measurements are used, then detection of aging phenomena is possible, but localization precision deteriorates due to approximately 1.2m accuracy of transit time measurement
Solution Approach 1:
The patent changes the measurement parameter from transit time (with 1.2m accuracy) to direct spatial mapping using terahertz wave reflection and absorption characteristics. This parameter change enables precise localization of insulation defects at the actual physical location rather than relying on time-based calculations with limited accuracy.
Solution Approach 2:
The patent transitions from one-dimensional transit time measurement to three-dimensional spatial mapping of insulation defects. By using the directional properties of terahertz radiation and multiple measurement angles, the system achieves precise localization in three-dimensional space, overcoming the limitations of scalar time-based measurement.
3Measurement precision
If high-voltage testing is used to detect signs of aging, then detection sensitivity is improved, but reliability deteriorates due to risk of irreparable breakdown
Solution Approach 1:
The patent converts the potentially harmful high-voltage stress into a harmless terahertz radiation measurement. Instead of applying high voltage that could cause breakdown, the system uses non-ionizing terahertz waves that provide equivalent detection sensitivity without the risk of damaging the insulation under test.
Solution Approach 2:
The patent replaces the expensive and risky high-voltage testing approach with a safe, non-destructive terahertz measurement method. The terahertz radiation acts as a disposable, harmless probe that provides sufficient detection sensitivity without requiring the extreme conditions that pose breakdown risks.
4Ease of operation
If endoscope or mirror is used to detect superficial defects, then ease of operation is improved, but detection capability deteriorates because deeper defects cannot be detected
Solution Approach 1:
The patent replaces the mechanical endoscope or mirror system with terahertz electromagnetic radiation. This substitution eliminates the need for physical contact or line-of-sight requirements, allowing penetration through insulation layers to detect deep-seated defects that mechanical methods cannot reach.
Solution Approach 2:
The patent makes the inspection system universal by using terahertz radiation that can detect both superficial and deep defects through the same measurement process. Unlike endoscopes that require different approaches for surface versus deep inspection, the terahertz system provides comprehensive detection capability across all depth ranges with a single method.
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 comprehensive detection and localization of insulation defects, reducing the risk of generator failure by allowing timely repairs and predicting service life, while being safe and cost-effective.
Implementation Method 1
Terahertz measurement technology is based on electromagnetic waves in the frequency range of 0.1 to 10 terahertz at wavelengths from 3 mm to 30 μm. Due to its low photon energy, terahertz radiation can penetrate non-conductive materials.
Implementation Method 2
generating precise 3D images of insulation defects using frequency-modulated continuous wave radar
Data Source
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AI summary
The invention relates to a method for the non-destructive testing of at least partial regions of an insulation (7) of a stator winding (1) of an electric machine (2), in particular a generator of a high-voltage motor, characterized in that the non-destructive testing is carried out in situ at the installation site of the electric machine (2) using terahertz measurement technology. The invention also relates to a testing device (24) for carrying out the method.