MI Cable Splice End Termination for High Voltage Compaction
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Solution Overview
Problem
Conventional mineral insulated (MI) cable splice designs are not suitable for high voltage and high temperature applications, as they fail to provide sufficient compaction of mineral insulation, leading to electrical breakdown and mechanical weaknesses, especially in subsurface environments where MI cables operate at elevated temperatures and voltages.
Innovation Solution
A fitting system for coupling insulated conductors that includes an end termination with separate openings for each conductor, a cylinder filled with electrically insulating material, and an end cap to seal the interior, ensuring compaction of the insulation and reducing electric field intensities to enhance operational reliability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MI cable splice designs are used, then the splicing process is simple, but the insulation compaction is insufficient leading to electrical breakdown at high voltages
Solution Approach 1:
The splice structure is divided into distinct functional segments: a compression fitting portion for mechanical assembly, an insulation portion containing the mineral insulation material, and a sealing portion. This segmentation allows each component to be optimized independently for its specific function while maintaining overall reliability at high voltages.
Solution Approach 2:
The mineral insulation material is pre-placed and pre-compressed within the insulation portion of the fitting before the conductors are inserted. This preliminary compaction ensures that the insulation is already dense and reliable before the final assembly, preventing electrical breakdown without requiring complex post-assembly compression mechanisms.
2Strength
If conventional splice designs are used, then the assembly process is fast, but the mechanical strength and insulation compaction are insufficient for high temperature applications
Solution Approach 1:
A compression fitting mechanism is employed that uses mechanical force applied through a compression tool to densely compact the mineral insulation material within the fitting. This hydraulic or mechanical compression system achieves high-density insulation compaction and strong mechanical bonding in a single rapid operation, suitable for high temperature applications.
Solution Approach 2:
The compression force applied to the mineral insulation material is controlled and optimized to achieve the desired density and mechanical strength. By adjusting compression parameters (force, duration, distribution), the insulation achieves maximum compaction without requiring extended assembly time, maintaining efficiency while improving strength.
3Reliability
If conventional splice designs are used, then the structure is simple, but leakage currents increase at high voltages due to insufficient insulation compaction
Solution Approach 1:
Mineral insulation material serves as an intermediary substance between the conductors and the external environment within the fitting. This material fills all gaps and voids, creating a continuous insulating barrier that prevents leakage current paths while maintaining a relatively simple overall structure.
Solution Approach 2:
The mineral insulation material is used in a compressed, dense state within the fitting to eliminate porosity and voids that would allow leakage currents. The material's inherent properties as a porous substance are utilized by compressing it to achieve maximum density, creating an effective electrical barrier without complex additional components.
4Temperature
If conventional MI cable splice designs are used, then the manufacturing process is straightforward, but the splices fail at high temperatures due to insufficient insulation density
Solution Approach 1:
The fitting combines multiple materials with complementary properties: metal components for structural strength and thermal resistance, mineral insulation material for electrical insulation and thermal stability, and sealing materials for environmental protection. This composite structure enables the splice to withstand high temperatures while maintaining electrical integrity.
Solution Approach 2:
The mineral insulation material is pre-prepared and pre-compressed to optimal density before final assembly. This preliminary preparation ensures that the insulation achieves maximum thermal and electrical performance without requiring complex high-temperature processing or curing steps during manufacturing, maintaining ease of manufacture.
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 proposed solution enables MI cables to operate reliably at high voltages and temperatures by ensuring sufficient compaction of insulation, reducing leakage currents, and increasing the margin between operating voltage and electrical breakdown, thus extending the lifespan and performance of the splices in harsh subsurface conditions.
Implementation Method 1
filling the cylinder with electrically insulating material such that the cores are substantially enclosed in the electrically insulating material
Implementation Method 2
ensuring compaction of the insulation
Data Source
AI summary
A fitting for coupling ends of cores of three insulated conductors includes an end termination placed over end portions of the three insulated conductors. The end termination includes three separate openings that pass through the end termination longitudinally. Each of the insulated conductors passes through one of the openings with end portions of the insulated conductors protruding from one side of the end termination. Exposed cores of the end portions of the insulated conductors protrude from the end termination. A cylinder is coupled to the side of the end termination from which the end portions of the insulated conductors protrude. An electrical bus is coupled to the exposed portion of the cores. Electrically insulating material fills the cylinder such that the cores are substantially enclosed in the electrically insulating material. An end cap is coupled to the cylinder to seal off the interior of the cylinder.