Split HF Coil Heating for Homogeneous Power Cable Insulation Curing

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Solution Overview

Problem

The conductor in existing induction heating systems acts as a heat sink, leading to non-homogeneous heating of the insulation layers during the restoration process of power cables.

Innovation Solution

An induction heating system with splitable high-frequency coils and a water-cooling system is used to heat the conductor from both inside and outside, ensuring homogeneous heating and curing of the insulation system layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the conductor is heated by induction coils from outside, then the insulation layers can be heated, but the conductor acts as a heat sink causing non-homogeneous heating

Engineering Contradiction:
Improveheating homogeneityVSAvoidheat sink effect
Core Design Contradiction:
TemperatureVSLoss of energy

Solution Approach 1:

Instead of heating the conductor from outside through insulation layers, the invention inverts the approach by heating the conductor from inside using induction coils wrapped around it. This reverses the heat flow direction, making the conductor the heat source rather than heat sink, and heat naturally flows outward to the insulation layers achieving homogeneous heating.

Inventive Principle:
Principle #13The other way round (Inversion)

Solution Approach 2:

The induction coils are nested directly around the conductor, with multiple layers of insulation wrapped around the coil-conductor assembly. This nested configuration ensures efficient heat transfer from the conductor through the insulation layers while maintaining compact structure and homogeneous temperature distribution.

Inventive Principle:
Principle #7Nested doll (Nesting)

2Device complexity

If a single induction coil is used, then the system is simpler, but the coil cannot be removed from the power cable after heating

Engineering Contradiction:
Improvecoil structureVSAvoidcoil removal
Core Design Contradiction:
Device complexityVSEase of operation

Solution Approach 1:

The induction coil system is divided into multiple separate coils, each designed to fit specific sections of the power cable. This segmentation allows individual coils to be easily removed after heating their respective sections, improving operational ease while maintaining system functionality.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The coil system is designed with flexible and adjustable characteristics, allowing coils to be dynamically positioned around the cable during heating and then easily removed or repositioned. This dynamic design enables both effective heating and easy removal without compromising structural integrity.

Inventive Principle:
Principle #15Dynamics

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 method achieves more uniform heating and curing of the insulation system layers, improving the integrity and reliability of power cable joints.

Implementation Method 1

The induction heating system induces a current into the conductor when the power cable is placed inside the first HF coil and the power supply system generates an alternating current, which induces a current in the conductor. The conductor is thus heated by the induced current.

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

The conductor is thus heated by the induced current

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Implementation Method 3

a water-cooling system configured to cool the first HF coil

Methodology Applied
Scientific EffectConvection cooling: Convection

Implementation Method 4

The pressurisation and heating device may comprise a heater integrated into or configured to be arranged or fitted inside the device. The restoration insulation system layer can thus be heated from the outside by means of the pressurisation and heating device

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP4114142B1Induction heating system and method for insulation system restoration of a power cable
Publication Date: 2025.12.10 NKT HV CABLES AB
  • EP4114142B1 patent drawingFigure 1~2
  • EP4114142B1 patent drawingFigure 3~4

AI summary

An induction heating system (1) for heating a conductor of a power cable to restore an insulation system of the power cable, wherein the induction heating system (1) comprises: a first high frequency, HF, coil (5) configured to receive the power cable, a water-cooling system (9) configured to cool the first HF coil (5), and a power supply system (3) configured to power the first HF coil (5), wherein the first HF coil (5) is configured to be openable or splitable into at least two parts.