Symmetrical Neutral-Strand Power Cable for EMC and Harmonic Heat
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Solution Overview
Problem
Conventional 3-phase power cables face issues with electromagnetic compatibility (EMC) due to harmonic-induced leakage currents and electromagnetic fields, which are exacerbated by high currents flowing through phase conductors, leading to excessive thermal loads on the neutral conductor.
Innovation Solution
The power cable features a conductor assembly with three phase conductors and multiple neutral conductor strands arranged in a rotationally symmetrical configuration around a central axis, distributing the neutral conductor currents and reducing electromagnetic interference by achieving perfect rotational symmetry, thereby minimizing electromagnetic radiation and thermal loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the neutral conductor is designed as a single solid conductor, then the cable structure is simple, but the thermal load and electromagnetic interference are excessive due to high harmonic currents
Solution Approach 1:
The neutral conductor is divided into multiple separate strands (at least two) instead of a single solid conductor. This segmentation reduces the skin effect and distributes the harmonic currents across multiple paths, thereby reducing the thermal load and electromagnetic interference while maintaining electrical conductivity.
2Temperature
If the neutral conductor is divided into multiple strands, then the thermal load is reduced, but the cable structure becomes more complex
Solution Approach 1:
The multiple neutral conductor strands are combined with the phase conductors in a single integrated cable assembly with a specific rotational symmetrical arrangement. This merging approach distributes the strands throughout the cable cross-section rather than grouping them separately, simplifying the overall structure while maintaining the thermal and electromagnetic benefits of multiple strands.
3Reliability
If individual conductors are installed separately, then the neutral conductor current capacity is sufficient, but electromagnetic field radiation increases
Solution Approach 1:
All conductors (phase conductors and neutral conductor strands) are merged into a single integrated cable assembly with a rotationally symmetrical cross-sectional arrangement. This configuration maintains adequate current carrying capacity while significantly reducing electromagnetic field radiation compared to separate conductor installation, as the symmetrical arrangement creates balanced electromagnetic fields that cancel each other out.
4Ease of manufacture
If the conductor assembly lacks rotational symmetry, then the manufacturing is easier, but the electromagnetic compatibility is poor
Solution Approach 1:
The conductor assembly is designed with rotational symmetry (3-fold or higher) around the central axis, where the phase conductors and neutral conductor strands are arranged in a balanced pattern. This symmetrical arrangement optimizes electromagnetic compatibility by creating balanced electromagnetic fields that minimize radiation and interference, while still being manufacturable through standard cable drawing processes.
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
This design enhances EMC properties, reduces the load on individual conductors, and prevents excessive thermal loading of the neutral conductor, ensuring reliable operation and efficient power transmission in 3-phase networks.
Implementation Method 1
Another problem is the potential radiation of electromagnetic fields due to the high currents. This problem is further aggravated when laying individual wires.
Implementation Method 2
EP 3 279 901 A1 discloses a power cable that addresses the problem of the skin effect. It involves splitting each phase conductor into two conductor strands
Implementation Method 3
Such power cables are used to supply electrical power to electrical consumers. Whenever reference is made to power cables, this means that each phase conductor is designed for a current of at least 50 A up to 1000 A.
Implementation Method 4
EP 2 027 589 B1 describes another power cable that addresses the problem of induction-induced currents in the protective conductor (earth conductor) in so-called TN-S networks.
Data Source
Figure 1~4
AI summary
The invention relates to a high-voltage cable (2) with a conductor assembly (4) comprising three phase conductors (6) and a neutral conductor, as well as a central axis (16) extending in a longitudinal direction (18), wherein the neutral conductor is divided into several neutral conductor strands (8) and the conductor assembly (4) with the three phase conductors (6) and the several neutral conductor strands (8) of the neutral conductor – viewed in cross-section – is designed rotationally symmetrical about the central axis (16) by an angle of rotation (α), wherein the angle of rotation (α) is given by: α = 360°/3n, where n is an integer. The symmetrical design and the division of the neutral conductor into the several neutral conductor strands (8) result in good EMC properties and, at the same time, reliable dissipation of currents caused by harmonics on the neutral conductor.