Flat Cable Short Circuit Prevention Fire Ceramifying Insulation
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Solution Overview
Problem
Conventional flat cables are prone to short circuits when exposed to fire, especially when laid on electrically conductive supporting bodies, due to the burning off of insulation and potential contact between wire conductors and the support body, which can lead to electrical contact and safety hazards during evacuations in large buildings or tunnels.
Innovation Solution
A flat cable design featuring parallel cores with ring-shaped core insulation made from ceramizing materials that form a ceramic crust upon burning, an intermediate sheath that spaces the cores, and a fire-resistant insulating layer between the intermediate and outer jackets to prevent short circuits, both between conductors and with conductive support bodies, while minimizing the use of ceramizing material for cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flat cables are used with standard insulation, then the cable structure is simple and cost-effective, but the cable is prone to short circuits when exposed to fire and laid on electrically conductive supporting bodies
Solution Approach 1:
The cable is divided into multiple functional layers: core insulation directly on conductors, intermediate sheath enclosing cores, fire-resistant insulating layer between intermediate and outer jackets, and outer jacket. This segmentation allows each layer to perform specific functions, with the fire-resistant layer providing short circuit prevention while other layers provide structural support and protection.
Solution Approach 2:
The fire-resistant insulating layer acts as an intermediary element between the intermediate sheath and outer jacket. This intermediate layer specifically addresses the short circuit risk by providing electrical insulation when the cable is laid on conductive supporting bodies, without requiring complete redesign of the entire cable structure.
2Reliability
If ceramizing insulating material is used in core insulation, then fire resistance is improved, but material cost increases
Solution Approach 1:
The ceramizing insulating material is applied locally only to the core insulation directly surrounding the conductors, rather than throughout the entire cable structure. This localized application provides fire resistance where it is most needed (at the conductor level) while minimizing the quantity of expensive ceramizing material required.
Solution Approach 2:
Instead of applying fire-resistant material throughout the entire cable, the solution uses partial action by concentrating ceramizing material only in the core insulation layer. The fire-resistant insulating layer between sheaths provides additional protection without requiring excessive ceramizing material, achieving adequate fire resistance with cost-effective material usage.
3Reliability
If the intermediate sheath reaches through between wires from one flat side to the other, then spacing between cores is maintained, but manufacturing complexity increases
Solution Approach 1:
The intermediate sheath is applied in advance during the cable manufacturing process, before the cable is installed. By pre-forming the sheath to reach through between wires from one flat side to the other, the core spacing is maintained during both manufacturing and subsequent installation, eliminating the need for complex adjustment procedures later.
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 design effectively prevents short circuits during fires by maintaining electrical insulation and spacing between cores and conductive support bodies, ensuring continued functionality of critical emergency systems and reducing the risk of electrical hazards, while being more cost-effective than traditional fire-resistant cables.
Implementation Method 1
at least one of the cores having the core insulation comprising insulating material extruded directly onto the core conductor and ceramifying in the event of a fire
Data Source
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AI summary
A flat cable (1) with short-circuit protection in case of fire, even when installed on an electrically conductive support structure, has at least two conductors (7, 7a) running parallel to each other in one plane. Each conductor (7, 7a) has a core (2) and an annular cross-sectional insulation (3, 10), wherein, in at least one of the conductors (7), the insulation (3, 10) comprises a ceramic-curing insulating material extruded directly onto the core (2) in case of fire. An intermediate sheath (4) encloses the conductors (7, 7a) and extends between each pair of conductors (7, 7a) from one flat side of the flat cable to the other. An outer sheath (6) surrounds the intermediate sheath (4) and defines the outer contour of the flat cable (1). At least one fire-resistant insulating layer (5) is arranged on the outside of the intermediate sheath (4). It lies between the intermediate mantle (4) and the outer mantle (6).