HVDC Cable Water-Blocking Compound for Insulation Protection

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Solution Overview

Problem

High voltage DC power cables operating at 320 kV or higher face issues with water migration due to non-solid conductors, which can lead to contamination of the solid insulation system, causing increased temperature and degradation over time.

Innovation Solution

A high voltage DC power cable design that includes a multi-wire conductor with a water-blocking compound to restrict water migration, eliminating the need for water swellable tapes and ensuring the solid insulation system remains contamination-free.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If water swelling tapes are used to prevent water migration, then water blocking capability is improved, but the solid insulation system becomes contaminated

Engineering Contradiction:

Improvewater blocking capabilityVSAvoidcontamination of solid insulation system

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent removes water swelling tapes from the cable structure entirely and replaces them with a water-blocking compound applied directly to the conductor. This extraction eliminates the source of contamination (tape components migrating into insulation) while maintaining water blocking functionality through the alternative compound application method.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the physical and chemical parameters of the water-blocking mechanism by using a compound with specific properties (viscosity greater than 20 Pa·s at 20°C, electrically conducting) rather than traditional water swelling tape materials. This parameter change allows water blocking without contamination of the insulation system.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If non-solid conductors with filling grade 92%-96% are used, then conductor flexibility is improved, but water migration risk increases

Engineering Contradiction:

Improveconductor flexibilityVSAvoidwater migration into interstices

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies the water-blocking compound to the conductor during the manufacturing process, before the cable is installed and before any water migration could occur. This preliminary action ensures that the compound is already in place to prevent water from entering the interstices between conductor wires when faults or defects occur during transport or installation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The water-blocking compound acts as an intermediary substance between the conductor wires and any potential water. It fills the interstices and creates a barrier that prevents water from migrating longitudinally into the conductor structure, while allowing the conductor to maintain its flexible stranded construction.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If water migration is prevented using traditional methods, then water blocking is achieved, but cable lifetime is reduced due to insulation degradation

Engineering Contradiction:

Improvewater blockingVSAvoidcable lifetime

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent converts the potential harm of having open interstices in the stranded conductor into a benefit by using those same interstices as a delivery pathway for the water-blocking compound. The compound is applied through the interstices and then prevents water from entering, turning the structural feature that could allow water migration into the mechanism for water protection.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent uses a water-blocking compound that provides long-term protection without requiring replacement or maintenance. Unlike water swelling tapes that may degrade and release contaminants over time, the compound remains stable and effective throughout the cable's operational life, actually extending rather than reducing cable lifetime.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 water-blocking compound effectively prevents longitudinal water migration, maintaining the integrity of the solid insulation system and extending the lifespan of the high voltage DC power cable by avoiding contamination and temperature-related degradation.

Implementation Method 1

The water-blocking compound may be hydrophobic

Methodology Applied

Scientific EffectHydrophobe: Hydrophobe

Implementation Method 2

a water-blocking compound configured to restrict water migration into the high voltage DC power cable

Methodology Applied

Scientific EffectAbsorption (physical): Absorption (physical)

Data Source

PatentEP3973556B9HVDC power cable with water-blocking capability

Publication Date: 2025.04.23 NKT HV CABLES AB

Figure 1~2
Figure 3~4

AI summary

A high voltage DC power cable (1-1) designed for voltages of 320 kV or higher, comprising: a multi-wire conductor (3), an inner semiconducting layer (5) arranged around the multi-wire conductor (3), the inner semiconducting layer (5) forming a screen layer for the multi-wire conductor (3), a solid insulation system (7) arranged around the inner semiconducting layer (5), and a water-blocking compound (15) configured to restrict water migration into the high voltage DC power cable (1-1).