RU47131U1 - FIRE RESISTANT ELECTRICAL CABLE - Google Patents

Abstract

The utility model relates to the construction of fire-resistant cables designed for operation in power circuits, as well as in control, monitoring and signaling circuits.

The cable contains one or more conductive wires with fireproof insulation, which consists of one or two glass mica, laid in the form of a winding in one direction with an overlap of at least 48%, polymer insulation, aggregate, no screen, with a screen or armor, an outer sheath. Polymer insulation and sheath are crosslinked by radiation modification or chemical method.

To increase the electrical strength of the insulation and increase resistance to bending, shock, vibration, each winding glass mica additionally contains a layer of organosilicon material in the form of a non-drying paste. Organosilicon paste is applied by brushing.

Description

The utility model relates to the field of electrical engineering, namely to the design of fire-resistant electrical cables intended for operation in power circuits, as well as in control, monitoring, signaling, communication and inter-instrument connection circuits for stationary installation.

The main indicators of fire resistance, characterizing the behavior of the cable when exposed to fire, are: a) fire resistance - the ability of a cable to transmit electrical energy during a fire; b) non-proliferation of combustion during single or bundle laying; c) reduced smoke emission; d) the absence of halogens in the smoke emitted during combustion or smoldering of the cable.

The fire resistance of the electric cable is ensured by fireproof insulation or an additional fireproof element of electrical insulation.

Known technical solutions for ensuring fire resistance through the use of glass and mica powder, or a ceramic coating with the addition of organosilicon resin and diluent (German application No. 3233504 from 09/09/1982, Japanese application No. 57-12248 from 09/21/1978, and No. 5712249 from 09.21.1978 g).

The disadvantages of these solutions are the significant complexity of cable manufacturing technology, low manufacturing productivity and toxicity of the ingredients used.

The prototype is a fire-resistant cable of the KPETI-FRHF brand, including several conductive cores, fire-resistant insulation from glass mica tape and polymer insulation from cross-linked polyethylene, a sheath of a halogen-free composition. The cable is designed to transmit electrical signals in circuits with voltages of up to 100 V. A glass mica tape consists of a glass tape, a layer of mica and a bonding silicone varnish (Journal of Cables and Wires No. 2, 2002, p. 45).

The main disadvantages of this cable include the fact that the insulation from the glass mica tape during bending of the core and cable during manufacture, installation and operation acquires multiple microcracks and does not provide electrical strength above 250-400 V when testing for fire resistance, and the shell with a short-term temperature increase above 120 ° C loses mechanical strength.

The basis of this utility model is the task of creating such a design of fire-resistant cable in which due to the new mutual arrangement of the insulation elements, the introduction of new elements and the use of new materials

the electric strength of the insulation was ensured at a voltage of more than 500 V, during and after exposure to fire, and the mechanical strength of the cable sheath would be increased with a short-term temperature increase above 120-140 ° C.

The task is achieved in that in a fire-resistant electrical cable that includes one or more conductive wires with flame-retardant and polymer insulation, the filler and the outer sheath, according to this utility model, the insulation of each core is made of two layers: the first fire-resistant layer is made in the form of a winding with one or two glass mica superimposed overlapping in one direction, and the second layer of insulation and / or the shell is made of crosslinked materials.

The advantage of the proposed fire-resistant cable option is that when two glass mica are applied, the electrical strength of the insulation increases, and the chemical or radiation crosslinking of the insulation material and the sheath ensures the cable is resistant to short-term temperature increases up to 200-250 ° C, oil resistance, and galling resistance.

Each layer of winding glass mica may additionally contain a layer of organosilicon material in the form of a non-drying paste.

To increase the electrical strength of the insulation from glass mica, reduce the dependence of fire resistance on mechanical factors (bending, vibration, shock), increase the reliability of the cable during a fire, it is proposed to apply silicone-based dielectric material in the form of a non-drying paste under the winding of glass mica.

Organosilicon material, filling all voids under and in the place of overlapping glass mica, increases the dielectric strength in the initial state. The non-drying paste reduces the destruction of glass mica during bending, thereby increasing the resistance of the cable to bending, shock, vibration. When exposed to temperatures above 750 ° C, the organosilicon material decomposes with the formation of dielectric ash, which increases the electrical strength of the insulation from glass mica. Increasing in volume, organosilicon ash fills all voids, providing additional insulation protection during and after a fire.

The cable can be additionally equipped with a shield of copper wires to protect against electromagnetic fields.

The cable can be optionally equipped with steel armor to protect against mechanical stress.

The proposed utility model is schematically depicted in figures 1 and 2.

Figure 1 shows a cross section of a fire-resistant cable, consisting of three insulated cores.

Figure 2 shows a longitudinal section of a separately insulated core.

Figures 1 and 2 show: 1-conductive core; 2-winding with two glass mica tapes; 3-layer organosilicon material; 4 polymer insulation;

5-placeholder, 6-screen in the form of a braid or wrapping with wires or ribbons of conductive material or armor made of metal, 7-outer shell.

Example. The fire-resistant electric cable shown in Fig. 1 contains three conductive conductors 1, fire-resistant insulation of each core, consisting of two glass mica 2, laid in one direction with a minimum of 48% overlap on high-speed winding machines and a layer of organosilicon material 3, polyethylene insulation 4, filler 5, screen 6 in the form of a braid of copper wires with a density of not less than 80% and a common sheath 6 of a halogen-free, non-combustible, low-smoke composition.

Insulation 4 and sheath 6 are crosslinked by radiation modification (under the action of irradiation with accelerated electrons) with a gel fraction of 75%. Crosslinking can also be carried out by the chemical method, with the help of organic peroxides introduced into the composition immediately before coating.

The fire-resistant insulated core shown in Fig. 2 contains a conductive core 1, a fire-resistant insulation, which consists of a layer of organosilicon material 3 deposited under each layer of winding with glass mica 2. As an organosilicon material 3, a composition based on polymethylsiloxane liquids or oligomeric compounds can be used. Such an oligomeric compound does not contain easily volatile solvents, is not toxic, the dry ash content after combustion is not less than 97% of the original, has a specific volumetric electrical resistance of at least 1 × 10 ¹⁴ Ohm.m, and electric strength of at least 12 kV / mm.

A layer of organosilicon material 3 is applied using a wipe method with the use of wipers, which greatly simplifies the manufacturing technology.

Claims (4)

1. Fire-resistant electrical cable containing one or more conductive conductors with flame retardant and polymer insulation, a filler, an outer sheath, characterized in that the fire-resistant insulation of each core is made in the form of a winding with one or two glass mica, superimposed overlapping in one direction, and polymer insulation and / or the outer shell is made of crosslinked materials. 2. The cable according to claim 1, characterized in that each layer of glass mica winding further comprises a layer of organosilicon material in the form of a non-drying paste. 3. The cable according to any one of claims 1 and 2, characterized in that it is additionally equipped with a screen of copper wires. 4. Cable according to any one of claims 1 and 2, characterized in that it is additionally equipped with steel armor.