HVDC Cable Termination with Segmented Insulating Fluids
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Solution Overview
Problem
High voltage direct current (HVDC) cable terminations face challenges in withstanding increasing voltage levels, maintaining reliable electrical performance, and ensuring mechanical integrity, particularly at the conductive shield termination where high electric field stress occurs.
Innovation Solution
A direct current cable termination apparatus with a tubular outer shell made of electrically insulating polymer material, featuring a partition that separates the termination space into two chambers filled with different insulating fluids (insulating gas and liquid filler) and incorporating an electric field control member within the liquid-filled chamber to manage electric field stress and improve insulation and mechanical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single insulating fluid is used in the outer shell, then the device complexity is reduced, but the insulation properties and electric field control are insufficient for high voltage levels
Solution Approach 1:
The space inside the outer shell is divided into two separate chambers (first chamber and second chamber) using a partition. Each chamber is filled with a different insulating fluid (first fluid and second fluid), allowing each fluid to perform its insulating function independently. This segmentation enables better electric field control and enhanced insulation properties without requiring a single complex fluid system
Solution Approach 2:
Different insulating fluids are used in different chambers based on their specific functional requirements. The first insulating fluid in the first chamber and the second insulating fluid in the second chamber can be selected with optimized properties for their respective locations, allowing local optimization of insulation performance and electric field management
2Reliability
If the conductive shield termination is exposed to atmosphere, then the ease of manufacture is improved, but the electrical performance deteriorates due to high electric field stress
Solution Approach 1:
The conductive shield termination is placed inside the second chamber which is filled with the second insulating fluid, creating a controlled inert environment. This protects the termination from atmospheric exposure and reduces electric field stress, improving electrical performance while maintaining reasonable manufacturing complexity through a straightforward sealing approach
3Power
If higher voltage levels are withstood, then the power transmission capability is improved, but the electric field stress at the conductive shield termination increases
Solution Approach 1:
By dividing the internal space into two chambers with different insulating fluids, the electric field stress is distributed and managed more effectively. The partition creates separate zones that can handle high voltage levels without concentrating excessive stress at the conductive shield termination point
Solution Approach 2:
The use of different insulating fluids with optimized electrical properties in the two chambers allows for better electric field distribution. The specific parameters of the insulating fluids (such as dielectric strength and electric field distribution characteristics) are selected to reduce stress concentration while maintaining high power transmission capability
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 electric field stress, enhances insulation properties, and improves mechanical performance, allowing the cable termination to withstand higher voltage levels and provide efficient sealing, thus addressing the limitations of existing HVDC cable terminations.
Implementation Method 1
The first chamber is filled with an electrically insulating first fluid in the form of an electrically insulating gas, and the second chamber is filled with an electrically insulating second fluid in the form of an electrically insulating liquid filler
Data Source
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AI summary
A direct current cable termination apparatus for terminating a high voltage direct current cable, the apparatus comprises a current-carrying device (102) comprising a terminal portion (104) of the direct current cable, the cable at least comprising an electrical conductor (106), a circumferential electrically insulating layer (108) located outside of the electrical conductor, and a circumferential conductive shield (110) located outside of the insulating layer and the electrical conductor. The apparatus comprises a housing (111) comprising an outer shell (112), and the current-carrying device (102) is adapted to extend in the axial direction of the outer shell. Along at least a part of the axial extension of the current-carrying device (102) the outer shell (112) extends axially with a space (118) between its inner periphery (114) and the current-carrying device. The apparatus comprises a partition (122; 222; 322) which separates the space into a first chamber (124) and a second chamber (126). The first chamber is filled with an electrically insulating first fluid (125) and the second chamber is filled with an electrically insulating second fluid (127) other than the first fluid. The conductive shield (1 10) terminates inside the second chamber, and at least one electric field control member (128) is located within the second chamber (126). An electric installation comprising the direct current cable termination apparatus.