Conductive Paint Coating for HV Apparatus Electron Emission Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High voltage instrument transformers with silicone-based gel insulation face challenges in cost efficiency due to the high expense of silicones and the need for large insulation volumes to maintain dielectric strength, as electron emission from metal electrodes can lead to avalanche ionization, necessitating increased dimensions and insulation distances.
Innovation Solution
Applying a solid insulating material coating on conductive elements in contact with the insulating gel to limit electron emission, thereby reducing the required insulation volume and improving dielectric withstand, allowing for smaller apparatus dimensions and reduced costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicone-based gel insulation is used to fill the free volume, then dielectric strength is improved, but apparatus dimensions and material cost increase
Solution Approach 1:
The patent applies different materials with different properties to different locations: conductive paint is applied specifically at electron emission sites (local treatment) rather than uniformly throughout. This allows the insulation system to have high dielectric strength where needed (at electrode surfaces) while using less expensive materials elsewhere, reducing overall insulation volume and cost.
Solution Approach 2:
The patent creates a composite insulation system combining silicone-based gel with conductive paint layers. The conductive paint (containing metal particles or carbon) forms a specialized interface layer with the gel insulation, creating a multi-material system that leverages the high dielectric strength of silicone while using the conductive properties of the paint to control electron emission and reduce required insulation distances.
2Reliability
If insulation distances are increased to prevent electron emission effects, then dielectric withstand is improved, but apparatus dimensions increase
Solution Approach 1:
The conductive paint is applied in advance to electrode surfaces to prevent electron emission before it can cause avalanche ionization. By creating a conductive barrier layer on the electrode surface, the system preemptively stops the harmful electron emission process, allowing for reduced insulation distances without compromising dielectric withstand.
Solution Approach 2:
The conductive paint acts as an intermediary layer between the metal electrode and the silicone gel insulation. This intermediate layer modifies the electric field distribution and prevents direct electron emission from the metal surface into the gel, allowing for more compact insulation design while maintaining dielectric performance.
3Reliability
If conductive paint is applied to limit electron emission, then dielectric strength is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the electron emission control function from the bulk insulation material and concentrates it in a separate conductive paint layer applied only where needed (at electrode surfaces). This separation allows the main gel insulation to focus on providing dielectric strength while the conductive paint handles electron emission control, simplifying the overall design despite the additional coating step.
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 coating effectively traps electrons, preventing ionization and enhancing the dielectric strength of the insulation system, enabling a reduction in the volume of insulating gel needed and lowering the overall cost of the instrument transformer.
Implementation Method 1
electrons are ejected from the cathodes into the gel by either field emission or by the field enhanced thermionic effect
Implementation Method 2
leading potentially to avalanche ionization of the atoms in the gel, caused by electron collision in the applied field
Implementation Method 3
The dielectric strength of the silicone gel determines the insulation distances between the elements in the insulation system
Data Source
AI summary
A high voltage (HV) apparatus insulated with an insulating gel includes at least two electrically conductive elements, such as a head transformer cover, a head housing base, a core casing, a primary conductor, bottom external housing, a bottom support flange, and/or a core. At least one of the electrically conductive elements has a coating made of solid insulating material separating the surface of the conductive element from the insulating gel and adapted for limiting electron emission from the conductive elements into the insulating gel.