HVDC Joint Box Insulating Layers for Electric Field Control
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Solution Overview
Problem
Ultra-high-voltage DC power cable joint boxes experience dielectric breakdown due to local electric field concentration, particularly at interfaces with different materials, leading to insulation weaknesses and heat generation issues.
Innovation Solution
The joint box design incorporates a first insulating layer with a specific thickness and a second insulating layer with lower volume resistivity, both made from materials like liquid silicone rubber and fluororubber, along with a glycol-based organic conductive filler, to alleviate electric field concentrations and prevent dielectric breakdown. The second insulating layer covers both electrodes, and a joint-box shielding layer is added to further shield external electric fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a joint box connects power cables with different material interfaces, then electrical connection is achieved, but electric field concentration occurs at the interfaces causing dielectric breakdown
Solution Approach 1:
The patent introduces a first insulating layer and a second insulating layer as intermediary components between the power cable and joint box components. The first insulating layer is provided between the power cable and the first electrode, while the second insulating layer is provided between the power cable and the second electrode. These intermediary insulating layers prevent direct contact between dissimilar materials, thereby eliminating electric field concentration at the interfaces and preventing dielectric breakdown.
2Adaptability or versatility
If different materials are used for insulating layers and electrodes, then functional requirements are met, but volume resistivity changes with temperature causing insulation weaknesses
Solution Approach 1:
The patent applies different insulating layers with specific properties at different locations within the joint box. The first insulating layer is positioned between the power cable and the first electrode, while the second insulating layer is positioned between the power cable and the second electrode. Each insulating layer is specifically designed for its local environment, with the second insulating layer having lower volume resistivity to provide stable electrical properties at the critical interface with the second electrode, thereby compensating for temperature-induced resistivity changes in other materials.
3Ease of manufacture
If a simple joint box structure is used, then manufacturing is easier, but electric field concentration occurs at material interfaces
Solution Approach 1:
The patent segments the insulating structure into multiple distinct layers: a first insulating layer and a second insulating layer with different volume resistivity characteristics. This segmentation allows each layer to perform a specific function in managing the electric field distribution. The second insulating layer with lower volume resistivity is strategically placed to address electric field concentration at the second electrode interface, while maintaining overall manufacturing feasibility through a systematic layered approach.
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 configuration effectively disperses electric fields, preventing dielectric breakdown and reducing heat generation at connection points, thereby enhancing the reliability and insulation performance of ultra-high-voltage DC power cable systems.
Implementation Method 1
a second insulating layer provided between the power cable and the second electrode, and having a volume resistivity lower than that of the first insulating layer
Implementation Method 2
a glycol-based organic conductive filler
Data Source
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AI summary
The present invention relates to a joint box for an ultra-high-voltage direct-current (DC) power cable and an ultra-high-voltage DC power cable system including the same. Specifically, the present invention relates to a joint box, for an ultra-high-voltage DC power cable, which is capable of alleviating an electric field in a region in which an electric field concentration occurs structurally to effectively prevent dielectric breakdown of the joint box due to a local electric-field concentration, and an ultra-high-voltage DC power cable system including the same.