HV Dry Instrument Transformer Capacitive Insulation
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Solution Overview
Problem
Existing high voltage dry instrument transformers face challenges due to their large size and weight, which lead to mechanical stresses and manufacturing difficulties, including chemical and thermal shrinkage of synthetic resins, resulting in voids or cracks and limiting the voltage level they can apply.
Innovation Solution
The use of column insulating bodies made of inorganic-filled hardenable resin with capacitive field grading layers and impregnation materials having similar thermal expansion coefficients, along with electrically conductive encapsulations, to create a compact and lightweight transformer design that minimizes mechanical stresses and prevents partial discharges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radial insulation distance is increased to guarantee dielectric strength due to nonuniform radial electric field, then the dielectric strength is improved, but the dimensions and weight of the apparatus substantially increase
Solution Approach 1:
The patent applies local quality by introducing field grading layers at specific locations where the electric field is most non-uniform. These grading layers locally modify the electric field distribution in the radial direction, reducing peak field stress without requiring uniform increase of insulation distance throughout the entire structure. This allows maintaining dielectric strength while minimizing overall dimensions and weight.
Solution Approach 2:
The patent uses composite materials consisting of multiple insulation layers with different dielectric properties. By combining materials with different permittivities in a layered structure, the electric field is redistributed to achieve more uniform field intensity across the radial insulation distance. This enables reduced insulation distances while maintaining required dielectric strength, thereby reducing weight.
2Reliability
If the size of the apparatus is increased to provide adequate insulation distances, then the dielectric strength is improved, but the mechanical stresses under dynamic loading increase
Solution Approach 1:
The patent applies local quality by introducing field grading layers at specific locations where the electric field is most non-uniform. These grading layers locally modify the electric field distribution in the radial direction, reducing peak field stress without requiring uniform increase of insulation distance throughout the entire structure. This allows maintaining dielectric strength while minimizing overall dimensions and weight.
Solution Approach 2:
The patent uses composite materials consisting of multiple insulation layers with different dielectric properties. By combining materials with different permittivities in a layered structure, the electric field is redistributed to achieve more uniform field intensity across the radial insulation distance. This enables reduced insulation distances while maintaining required dielectric strength, thereby reducing weight.
3Reliability
If the size of the apparatus is increased to provide adequate insulation distances, then the dielectric strength is improved, but the manufacturing difficulty increases due to chemical and thermal shrinkage causing voids or cracks
Solution Approach 1:
The patent applies segmentation by dividing the insulation system into multiple discrete layers with field grading interfaces. This segmented structure allows each layer to be manufactured and cured separately with controlled shrinkage, preventing the accumulation of stresses that would cause voids or cracks in a monolithic large-scale structure. The modular approach facilitates easier manufacturing while maintaining dielectric strength.
Solution Approach 2:
The patent changes material parameters by selecting insulation materials with matched thermal expansion coefficients and controlled shrinkage characteristics. By carefully selecting and matching material parameters across different layers, the patent minimizes differential thermal stresses during curing and operation, preventing void formation and cracking even in larger apparatus.
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 design achieves a compact and lightweight transformer with uniform electric fields, reducing mechanical stresses and manufacturing issues, while maintaining high dielectric strength and preventing electrical failures.
Implementation Method 1
the column insulating bodies have an impregnation material having substantially the same coefficient of thermal expansion as the material of the insulating members
Implementation Method 2
the column insulating bodies have a form of a dry capacitor bushings, wound as a block of spacer sheet
Data Source
Figure 1
Figure 2~5
AI summary
The subject of invention is a HV dry instrument transformer based on a new type of dry insulation system. High-voltage instrument transformer has a form of current transformer (1) or a voltage transformer (21). The column insulating body (11) or (29) of the instrument transformer has a form of a dry capacitor bushing wound as a block of spacer sheet (9) or (30), respectively. The current transformer (1) has a head insulating body (13) for electrical insulation of the secondary winding assembly (8) from the primary winding conductor (12), For the current transformer (1) the head insulating body (13) has a form of a capacitor bushing and is in contact with the insulating member (18). The voltage transformer (21) has a primary winding (24) which is in contact with the insulating member (32). The column insulating body (11) or (29) has an impregnation material having substantially the same coefficient of thermal expansion as the material of the insulating member (18) or (32), respectively.