Power Cable Insulation Joint With Tapered Tape Edge Control
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Solution Overview
Problem
The existing insulation system of power cables, particularly in factory joints, faces issues with edge formation between the inner and outer semiconducting layers during the heating process, leading to increased electric fields and potential insulation breakdown due to the differential softening rates of the tape and semiconducting layers.
Innovation Solution
A method involving a tapering tape with a decreasing thickness towards its edges, wound in overlapping layers and heated under pressure, to reduce edge formation and enhance the filling factor, is used to create a seamless insulation system between sections of a power cable, ensuring a smooth thickness transition and symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If tape with uniform thickness is used during heating process, then the heating process is simple, but edges form between the insulation layer and semiconducting layers due to differential softening rates
Solution Approach 1:
The tape is designed with non-uniform thickness distribution, where the thickness varies along the width of the tape. Specifically, the tape has a greater thickness at the center portion and a reduced thickness at the edge portions. This local variation in thickness compensates for the differential softening rates between the tape and semiconducting layers during heating, preventing edge formation while maintaining manufacturing simplicity.
Solution Approach 2:
The physical parameter of tape thickness is changed along its width to address the edge formation problem. By controlling the thickness parameter to be non-uniform (greater at center, reduced at edges), the tape compensates for differential thermal softening during the heating process, thereby preventing edge formation between layers without complicating the manufacturing process.
2Reliability
If tape edges overlap during winding, then complete coverage is achieved, but edge formation occurs during heating due to differential softening
Solution Approach 1:
The tape incorporates local quality variation through non-uniform thickness distribution. The edge portions have reduced thickness compared to the center portion, which compensates for the differential softening behavior during heating. This allows the tape edges to overlap during winding for complete coverage while preventing edge formation during the subsequent heating process.
3Stability of the object's composition
If the insulation system is extruded, then the insulation system is continuous, but factory joints are not easily detectable and may have hidden defects
Solution Approach 1:
The invention employs visual differentiation through color or marking changes at factory joint locations. By incorporating detectable visual indicators (such as colored bands, markers, or contrasting colors) at the joints between extruded insulation sections, the continuity of the insulation system is maintained while enabling easy detection and identification of joint locations for quality control and inspection purposes.
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 approach significantly reduces the risk of edge formation during the heating process, maintaining the integrity of the insulation system and enhancing the filling factor, thus preventing insulation breakdown and ensuring reliable cable performance.
Implementation Method 1
heating the plurality of layers of tape to melt and fuse the plurality of layers of tape to form an insulation system layer
Implementation Method 2
heating the plurality of layers of tape to melt and fuse the plurality of layers of tape
Implementation Method 3
the inner semiconducting layer and the outer semiconducting layer during the heating process
Data Source
Figure 1~3c
AI summary
A method of building an insulation system around an axial section of a conductor (5) of a power cable (1), the method comprising: a) providing a power cable (1) including a conductor (5) and an insulation system (7a, 7b, 9a, 9b, 11a, 11b) arranged around the conductor (5), the insulation system (7a, 7b, 9a, 9b, 11a, 11b) comprising insulation system layers, including an inner semiconducting layer (7a, 7b) arranged around the conductor (5), an insulation layer (9a, 9b) arranged around the inner semiconducting layer (7a, 7b), and an outer semiconducting layer (11a, 11b) arranged around the insulation layer (9a, 9b), wherein the power cable (1) comprises an axial section between a first insulation system section and a second insulation system section of the insulation system (7a, 7b, 9a, 9b, 11a, 11b) which at least is without an outer semiconducting layer (19), b) winding a tape around the conductor (5) along the axial section in a plurality of layers to form a plurality of layers of tape connecting with the first insulation system section and the second insulation system section, and c) heating the plurality of layers of tape to melt and fuse the plurality of layers of tape to form an insulation system layer (17; 19) between the first insulation system section and the second insulation system section, wherein the tape has a width defined by a distance between lateral edges, wherein the tape has a mid-section between its lateral edges, wherein in the mid-section the tape has a largest thickness, and wherein the thickness of the tape decreases from the mid-section towards both lateral edges.