Electrostatic Shield Embedded in Transformer Resin
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Solution Overview
Problem
Uncontrolled electrostatic field stress between high and low voltage conductors in split core current transformers can cause partial discharges, leading to erosion of insulating materials, and existing electrostatic shields are not sufficient to mitigate this issue effectively.
Innovation Solution
An electrostatic shield embedded in a polymer resin encasement is positioned between the high voltage conductor and the low voltage winding, extending laterally through the encasement and connected to the high voltage conductor, preventing a continuous conductive path and reducing electrostatic field stress without contacting the low voltage winding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electrostatic shield is added to reduce electrostatic field stress, then reliability is improved, but device complexity increases
Solution Approach 1:
The electrostatic shield is embedded within the polymer resin encasement, nesting the shield inside the existing transformer housing structure. This integration approach reduces the need for separate mounting structures and external components, thereby improving reliability through better field control while minimizing the increase in device complexity.
Solution Approach 2:
The shield utilizes a thin conductive layer embedded in the polymer resin encasement rather than a bulky rigid structure. This thin-film approach provides effective electrostatic shielding while maintaining a compact design, thus improving reliability without significantly increasing device complexity.
2Reliability
If the electrostatic shield is positioned closer to the high voltage conductor, then electrostatic field stress reduction is improved, but the risk of partial discharge increases
Solution Approach 1:
The polymer resin encasement serves as an intermediary material between the electrostatic shield and the high voltage conductor. This dielectric barrier allows the shield to be positioned close to the conductor for effective field control while the resin insulation prevents direct contact and eliminates the risk of partial discharge through the intermediary protective layer.
Solution Approach 2:
The electrostatic shield is connected to the high voltage conductor to maintain the same electrical potential. By keeping the shield at equipotential with the conductor, no potential difference exists between them, eliminating the driving force for partial discharge while still providing effective electrostatic field stress reduction.
3Ease of manufacture
If the electrostatic shield is embedded in the polymer resin encasement, then manufacturing ease is improved, but the shield's electrical connection becomes more difficult
Solution Approach 1:
The electrostatic shield is combined with the polymer resin encasement into a single integrated component during the molding process. This merging of the shield and encasement simplifies manufacturing by reducing the number of separate parts and assembly steps, while the electrical connection is simultaneously integrated through conductive pathways built into the resin structure.
Solution Approach 2:
The polymer resin encasement serves multiple functions: it provides mechanical protection, electrical insulation, and simultaneously serves as the medium for embedding the electrostatic shield and providing its electrical connection. This multi-functionality reduces the need for separate components and simplifies the overall manufacturing process.
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
The solution effectively reduces electrostatic field stress, preventing partial discharges and extending the lifespan of insulating materials by maintaining the electrostatic shield at the same potential as the high voltage conductor, thus enhancing the reliability of split core current transformers.
Implementation Method 1
control of electrostatic field stress in a split core instrument transformer
Implementation Method 2
An electrostatic shield is provided for connection to the elongated conductor
Implementation Method 3
A second encasement formed of a polymer resin encapsulates the electrostatic shield, the low voltage winding, and the second core segment
Data Source
AI summary
An electrostatic shield for controlling the electrostatic field between a high voltage conductor and a low voltage conductor in an instrument transformer is provided. The instrument transformer has a current transformer and a voltage transformer. The current transformer has a split core which includes a first core segment and a second core segment. When the first core segment adjoins the second core segment, a current transformer is formed, having a core formed from the first and second core segments. The high voltage conductor runs between the first and second core segments of the current transformer. The first core segment is encapsulated in a polymer resin and when encapsulated, forms a first encasement. The second core segment has a low voltage winding mounted thereon. The electrostatic shield is disposed between the low voltage winding and the high voltage conductor. A second encasement is formed by encapsulating the electrostatic shield, low voltage winding and second core segment in a polymer resin.