JPH0265004A - Electric cable - Google Patents

Abstract

PURPOSE:To extinguish a fire by themselves even if electric cables having 3KV or more using inflammable crosslinked polyethylene as an insulator are multi-laid, and prevent noxious gas and smoke from occurring by providing a specific heat resistant plastic film under an outermost plastic sheath. CONSTITUTION:Around a conductor 1, there are provided in order an inner semi-conductor layer 2, a crosslinked polyethylene insulating layer 3, an outer semi-conductor layer 4 and a shielding layer 5 made of a metallic wire. Furthermore, there are disposed a heat resistant plastic tape wound layer 6 not including halogen OI of 30 or more and a plastic sheath 7 not including halogen of an outer layer. Namely, if a fire occurs and spreads to cables so that, in the initial stage of the fire, the crosslinked polyethylene disposed inside is heated into a molten state and followed by expansion, the heat resistant tape can escape cutting into a molten state and delay effusion or dropping. In addition, since flame retardance of the tape isn't lowered, the spread of a fire to the tape is little. Therefore, in the case of vertical multi-laying, the cables can extinguish a fire by themselves at a fire, and moreover, noxious gas and smoke nearly occur.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to polyethylene power cables, particularly cross-linked polyethylene power cables, which have improved self-extinguishing properties in fire special properties.

(Prior art) (Problems to be solved by the invention) Conventional 3 ν
In the above-mentioned crosslinked polyethylene electrical cable, polyethylene or vinyl chloride resin is used as the sheath material.

When polyethylene is used as the sheath, there is little risk of generating harmful gases during combustion, but if it ignites when vertically installed in multiple strips, the fire will easily spread and the cable will burn out.

When vinyl chloride resin is used as a sheath, it exhibits self-extinguishing properties when installed vertically due to the presence of chlorine, but it generates a large amount of hydrogen halide gas (HCI! gas), which corrodes surrounding equipment and poses a threat to humans and animals. Because it is harmful to people, it has the disadvantage of easily inducing secondary disasters such as fire.

Note that when multiple cables are installed using vinyl chloride resin as a sheath, self-extinguishing properties of ordinary vinyl chloride resin are insufficient, so PvC materials such as highly halogenated paraffin may be mixed in for more advanced flame retardancy. The fact that smoke and harmful gases generated during a fire can cause secondary disasters is no different from the former vertical-row installation.

As mentioned above, with conventional technology, electric cables with a power capacity of 3 to ν or more that use flammable cross-linked polyethylene as an insulator are self-extinguishing even when laid in multiple strips, and generate almost no harmful gas or smoke. Currently, such low-disaster countermeasures have not yet been established.

By the way, there are already examples of attempts to make 600 V electrical cables, control cables, and communication cables self-extinguishing and non-halogenated, but the cable structure is flammable and the cross-linked polyethylene insulation has a large volume. Currently, the sheath of electric cables has not been made halogen-free and has high flame retardancy.

Additionally, in order to prevent the spread of fire in the cross-linked polyethylene that makes up the insulator, it is possible to apply metal tape, metal/glass tape, mica tape, ceramic paper, etc. under the sheath (on the inside); however, when using metal tape, requires an electrical connection with the shielding layer applied to the cable,
Furthermore, due to the difference in metal used for the shield layer, there is a risk of galvanic corrosion due to contact between dissimilar metals, and when applying mica/glass tape, the mica may peel off during the tape winding process, and there may be mechanical elongation due to cutting the glass. In addition, even when ceramic paper is used, ceramic paper does not stretch, so there are problems such as difficulty in tape winding.

(Means for Solving the Problems) The present invention was made as a result of intensive studies to solve the problems of the conventional technology. A shielding layer such as metal tape or metal wire is applied to the outside of the cable core, the outermost layer is a halogen-free plastic sheath, and the underside of this plastic sheath has an OI of 30 or more and does not contain halogen. This is an electric cable made of heat-resistant plastic film.

Next, the present invention will be explained in detail with reference to the drawings.

Figure 1 shows an example of a single-core cable, in which an inner semiconducting layer 2, a crosslinked polyethylene insulating layer 3, and an outer semiconducting layer 4 are sequentially applied to the outside of a conductor 1, and a jacket made of metal wire or metal tape is applied on top of this. A layer 5 is applied, and on the outside thereof a halogen-free heat-resistant plastic tape wrapping layer 6 having an o* of 30 or more is applied, and then a halogen-free plastic sheath 7 is applied.

FIG. 2 shows an example of a three-core cable, in which three wire cores are sequentially coated with an internal semiconductive layer 2, a crosslinked polyethylene insulating layer 3, and an external semiconductive layer 4 on the outside of a conductor (2), and are twisted together with an intervening material (8). A shielding layer 5 made of metal wire or metal tape on the outside, OI
A halogen-free heat-resistant plastic tape winding M6 having a halogen-free temperature of 30 or more and a halogen-free heat-resistant plastic sheath 7 are sequentially provided.

The heat-resistant plastic tape that does not contain halogen and has an OI of 30 or more used in the present invention is polyether ether ketone, polyetherimide, polyarylate, polyimide, polyether sulfone, polysulfone, etc., and has a halogen in its molecular structure. Those that do not contain are selected, especially considering the generation of harmful gases during combustion.
If you want to suppress the generation of SO□, HCN gas, etc., add S in the molecules of polyetheretherketone, polyarylate, etc.
, It can be said that a composition not containing N is preferable.

In addition, when making this into a tape, the thickness of the tape should be determined from the viewpoints of ease of winding, flexibility of the cable, and prevention of the melted material of the crosslinked polyethylene insulator inside the tape from blowing out. The thickness is preferably 10 μm or more and 550 μm or less.

Heat-resistant tapes such as those mentioned above have an OI of 30 or more, and even if the cross-linked polyethylene inside the cable is heated and melted and expanded in the initial stage of the fire, it will not break until it reaches around 400°C. It does not melt and plays a role in delaying the blowing and dripping of cross-linked polyethylene.

Furthermore, this tape is flame retardant, and its flame retardancy hardly decreases between room temperature and 300°C, so the spread of fire in the heat resistant tape itself is small.

Furthermore, since this heat-resistant plastic tape has more elongation than non-flammable tapes such as glass tape, there is no risk of wrinkles or cuts during tape winding.

Furthermore, since these heat-resistant tapes carbonize when the cable burns, it is possible to further improve the effect of preventing the spread of cable fire by wrapping a protective tape such as glass cloth over it in order to protect the formation of the carbonized heat-insulating layer. .

If semiconductive paper, cotton tape, or heat-resistant tape is applied to the inside of the barrier layer made of metal wire or metal tape, the carbonized heat-insulating layer described above will be formed. It can be applied directly on top of the conductive layer.

Next, examples of the present invention are shown in Table 1, and comparative examples are shown in Table 2, to clarify their structures and characteristics.

In all of the examples in Table 1, halogen flame-retardant and heat-resistant tape is applied under the sheath, and the sheath is 0r30.
It is equipped with a non-halogen flame retardant sheath.

The comparative example shown in Table 2 has a structure that is outside the scope of the present invention in any part of the cable structure.

As is clear from Tables 1 and 2 above, the product according to the present invention is It! BE! In the Scd 383 combustion test, it self-extinguished and produced very little smoke or harmful gas.

In addition, the workability of tape winding was good and there were no problems in cable production. On the other hand, the following notable problems were observed in the comparative example.

Example 1. Even if a non-halogen sheath of 0130 or higher is used for the sheath, it will burn out if there is no heat-resistant tape.

Example 28 Example 3. If non-combustible tape is applied, the fire will self-extinguish, but tape winding workability is poor.

Example 4. The vinyl chloride sheath (Or = 24) was completely burnt out,
It also generated a large amount of harmful smoke and gas.

Example 5. When a highly flame-retardant vinyl chloride sheath (Of = 35) is used, the fire extinguishes itself, but as in Example 4, it is recognized that a large amount of noxious gas and smoke is generated.

Example 6. Heat-resistant tape was applied, but since the flame retardance of the non-halogen sheath was insufficient (OI = 24), it burned down completely.

(Effect of the invention) In the case of the above cross-linked polyethylene insulated cable, even if it is laid vertically in multiple strands, it can self-extinguish in the event of a fire. ■The cable component material does not contain any halogen, and there is no generation of hydrogen halide gas such as hydrogen chloride that is harmful in the event of a fire, and there is almost no smoke. ■Unlike non-flammable tape, it is stretchable. Heat-resistant resin tape is easy to wrap.

[Brief explanation of the drawing]

1 to 1 are cross-sectional views of embodiments according to the present invention. ■...Conductor, 2...Inner semi-conducting layer, 3...Crosslinked polyethylene insulating layer, 4...Outer semi-conducting layer, 5...Break layer made of metal wire or metal tape, 6 ...O
I: Non-halogen heat-resistant plastic tape of 30 or more, 7... OI: Non-halogen plastic sheath of 30 or more, 8... Intervening agent: Patent attorney Mamoru Takeuchi

Claims (1)

[Claims] A metal shielding layer such as metal tape or metal wire is applied to the outside of the single core or multi-core strand of an insulated wire core with at least cross-linked polyethylene insulation on the conductor, and the outermost layer is a halogen-free plastic. A power cable comprising a sheath and one or more types of heat-resistant plastic tape having an OI of 30 or more and containing no halogen applied to the underside of the sheath.