HVDC Cable Sleeve with Composite Insulation
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Solution Overview
Problem
High-voltage polymer cable joints face challenges in achieving uniform electrical field distribution and high electrical strength over a large temperature range due to the temperature-dependent specific electrical resistances of insulating materials, and existing solutions like non-linear resistive field control materials can be prone to puncture under surge voltage stress.
Innovation Solution
A joint for HVDC polymer cables uses a sleeve body with at least two insulating elastomers having different electrical properties, arranged to ensure a continuous connection without interfaces in critical areas, utilizing materials like cross-linked polyethylene and silicone or EPR elastomers, which reduces temperature-dependent field distribution issues and enhances surge voltage resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single insulating material is used in the sleeve body, then the structure is simple and easy to manufacture, but the electric field distribution becomes non-uniform over a wide temperature range due to temperature-dependent specific electrical resistances
Solution Approach 1:
The sleeve body uses a composite insulation structure comprising at least two different insulating materials with different specific electrical resistance characteristics. This composite structure enables uniform electric field distribution across a wide temperature range by compensating for the temperature-dependent resistance variations of individual materials, while maintaining manufacturing feasibility through standardized production processes.
2Reliability
If non-linear resistive field control materials are used to achieve uniform field distribution, then the electric field uniformity is improved, but the electrical strength under impulse voltage stress decreases making the material prone to puncture
Solution Approach 1:
The patent applies different insulating materials in specific spatial locations within the sleeve body. The first insulating material is placed in regions requiring field control, while the second material with higher electrical strength is positioned in areas exposed to high impulse voltage stress, such as between the deflector and cable insulation. This local differentiation simultaneously achieves uniform electric field distribution and maintains high electrical strength where needed.
3Reliability
If interfaces between different insulating materials are present in critical areas, then the field control capability is improved, but the dielectric strength decreases creating weak points under high electric field stress
Solution Approach 1:
The patent extracts the interface between different insulating materials from the critical high-field region between the deflector and cable insulation. By positioning the interface outside this critical area, the design eliminates the creation of weak points in regions subjected to high electric field stress during impulse voltages, while still maintaining effective field control capabilities through the differentiated material structure.
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 provides a more uniform electrical field distribution and high electrical strength over a wide temperature range, preventing breakdowns and avoiding punctures during surge voltage stress by eliminating interfaces in critical areas, thus improving the reliability of HVDC cable joints.
Implementation Method 1
the electric field distribution when several insulating materials are combined depends on the specific electrical resistance of the materials involved. The field distribution between two different materials is generally given by the ratio of their specific resistances.
Implementation Method 2
the specific electrical resistances of these materials change with temperature, and this temperature dependence of the specific resistances depends on the respective materials
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a sleeve body, made from elastomers for connecting high-voltage polymer cables for direct current. The insulation of the sleeve body comprises two insulation materials which have different electrical properties. By using two insulation materials with different specific electrical resistances, a more uniform distribution of the electrical field can be achieved in the sleeve body across a large temperature range. It is therefore important that the insulation material with the lower specific electrical resistance (5) forms a continuous connection between the deflector (4) and the center electrode (7) in the sleeve body. In order to guarantee a high electrical dielectric strength under surge voltage, it is likewise important that no boundary surface is located between the insulating materials within the sleeve body in the electrically critical area between the deflector (4) and the cable insulation (1).