Termination Cable Layout for Lower-Stress Power Cable Ends

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Solution Overview

Problem

Existing cable termination devices face challenges with high temperatures and electric fields, leading to thermal runaway, mechanical stress, and material degradation, especially in DC applications, with current solutions being costly and risky.

Innovation Solution

A power cable termination system using a termination cable that is one order of magnitude shorter than the power cable, with a lower electrical resistance and higher insulation resistance per unit length, allowing for a scaled-down cable termination device and reduced thermal and electric field stress, enabling the use of less hazardous insulating fluids and a standardized design for various power cable types.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a stress cone or field-grading adapter is placed around the power cable to reduce electric field, then electric field stress is reduced, but device complexity and material selection constraints increase due to high temperature and electric field conditions

Engineering Contradiction:
Improveelectric field stress reductionVSAvoiddevice complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the problematic power cable directly from the termination device by using an underground cable trench. The power cable is buried in the ground and only the termination point connects to the termination device, effectively removing the cable from the high-stress environment inside the termination device while maintaining electrical connection functionality.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces ground (earth) as an intermediary medium between the power cable and the termination device. The cable is laid in a cable trench filled with soil, which acts as a thermal sink and electrical reference, mediating the interaction between the cable and termination device while reducing electric field stress and thermal runaway risks.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If cable thickening is performed by lapping/vulcanization or insulating adapters to handle high electric fields, then electric field stress is reduced, but manufacturing time and quality risks increase significantly

Engineering Contradiction:
Improveelectric field stress reductionVSAvoidmanufacturing time and quality risk
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

Instead of modifying the cable or adding complex insulation layers, the patent extracts the cable from the problematic termination device environment by burying it in ground. This eliminates the need for cable thickening operations, lapping/vulcanization processes, and insulating adapter installations, dramatically simplifying manufacturing while maintaining reliability.

Inventive Principle:
Principle #2Taking out (Extraction)

3Reliability

If forced cooling or material modification is applied to reduce temperature, then thermal runaway risk is reduced, but device complexity and development cost increase

Engineering Contradiction:
Improvethermal runaway risk reductionVSAvoiddevice complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent removes the power cable from the confined, high-temperature termination device by burying it in an underground cable trench. This extraction eliminates the need for forced cooling systems, thermal management materials, and temperature control mechanisms within the termination device, reducing complexity while maintaining thermal safety.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses ground (earth) as an inert thermal environment for the cable. The soil surrounding the cable in the trench acts as a natural thermal sink and protective medium, creating a stable, inert environment that prevents thermal runaway without requiring active cooling or special thermal materials in the termination device.

Inventive Principle:
Principle #39Inert atmosphere (Inert environment)

4Ease of operation

If the power cable is placed directly in the termination device, then installation is simple, but high temperature and electric field cause thermal runaway and material degradation

Engineering Contradiction:
Improveinstallation simplicityVSAvoidthermal and electric field stability
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The patent segments the cable system into two distinct parts: the power cable buried in the ground (outside the termination device) and the termination device itself. This segmentation allows each component to operate in its optimal environment - the cable in the cool, stable ground and the termination device with reduced thermal and electric field stress - while maintaining electrical connectivity.

Inventive Principle:
Principle #1Segmentation

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 system reduces installation time and costs, minimizes thermal and electric field risks, and allows for pre-production and storage of cable termination devices, enhancing safety and efficiency.

Implementation Method 1

the termination cable conductor has an electrical resistance which is lower than an electrical resistance of the power cable conductor

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Implementation Method 2

the termination cable insulation system has a higher insulation resistance per unit length than the power cable insulation system

Methodology Applied
Scientific EffectElectric field: Electric Field

Data Source

PatentEP3981051B1Power cable termination system
Publication Date: 2025.12.03 NKT HV CABLES AB
  • EP3981051B1 patent drawingFigure 1~3
  • EP3981051B1 patent drawing

AI summary

A power cable termination system (l) comprising: a power cable (3) having a power cable conductor (3a) and a power cable insulation system (3b) configured to electrically insulate the power cable conductor (3a), a termination cable (7) having a termination cable conductor (7a) and a termination cable insulation system (7b) configured to electrically insulate the termination cable insulation system (7b), wherein the termination cable (7) is at least one order of magnitude shorter than the power cable (3), wherein the termination cable conductor (7a) has an electrical resistance which is lower than the electrical resistance of the power cable conductor (3a) and/ or the termination cable insulation system (7b) has a higher insulation resistance per unit length than the power cable insulation system (3b), a joint (5) configured to join the power cable (3) and the termination cable (7), and a cable termination device (9) configured to terminate the termination cable (7).