RU81368U1 - COAXIAL CABLE FOR TRANSMISSION AND DISTRIBUTION OF ELECTRIC ENERGY - Google Patents

Abstract

The proposed coaxial cable is designed for transmission and distribution of electrical energy in power and lighting networks with a rated alternating voltage of up to 380 V and a frequency of 50 Hz. The objective of the utility model is to increase the reliability and safety of operation of power and lighting networks with the exception of the possibility of unauthorized connection of consumers to these networks. To solve this problem, it is proposed in a coaxial cable that the inner conductor be single-core or multi-core of copper or aluminum wires twisted together in a core. To increase the reliability of the cable and eliminate its stretching and sagging, it is proposed that some of the conductors of the internal and external conductors be made in the form of reinforcing elements - galvanized steel wires. The number of steel wires is determined by the required breaking force, which the cable must withstand.

Description

The proposed coaxial cable is designed for transmission and distribution of electrical energy in power and lighting networks with a rated alternating voltage of up to 380 V and a frequency of 50 Hz.

Known cable AVT-1 (AVT-2), which is 2, 3 or 4 insulated conductors twisted around an insulated steel cable, used as branches from high-voltage lines. The use of this cable does not exclude the possibility of unauthorized connection of the consumer, bypassing metering devices.

Power cables with external wire armor are known (Bachelis D.S. et al. Electrical cables, wires and cords (reference), under the general editorship of N.I. Belorussov. 3rd edition, revised M., "Energy ", 1971, p. 76). Known cables comprise an internal insulated conductor, with wire armor overlaid on the insulation, which is coated with an outer sheath. In this cable design, the possibility of unauthorized connection of consumers to power lines is also not ruled out.

Closest to the proposed technical solution is a coaxial cable according to RF patent No. 33669, which contains an internal single-core conductor, insulation of the internal conductor, an external multicore conductor, and insulation of an external multicore conductor. This cable design eliminates the possibility of unauthorized connection of consumers to power lines, since it is impossible to connect to the core of the inner conductor without damaging the outer conductor. A significant drawback of this cable is its considerable stretching and sagging during operation on overhead lines, which reduces the reliability and safety of power and lighting networks.

The objective of the utility model is to increase the reliability and safety of operation of power and lighting networks with the exception of the possibility of unauthorized connection of consumers to these networks.

To solve this problem, it is proposed in a coaxial cable consisting of an inner conductor, insulation of the inner conductor, on which an outer multicore conductor of aluminum wires and an outer insulating sheath, an inner conductor are concentrically laid

perform single-core or multi-core of copper or aluminum wires twisted together in a core. To increase the reliability of the cable and eliminate its stretching and sagging, it is proposed that some of the conductors of the internal and external conductors be made in the form of reinforcing elements - galvanized steel wires. The number of steel wires is determined by the required breaking force, which the cable must withstand, and is determined by the formula:

Where

n is the number of steel wires,

k - safety factor equal to 1.4 to 1.5,

P - breaking strength of the cable (N),

S is the nominal cross section of the inner, outer conductor (mm ² ),

δ ₁ - temporary tensile strength of the inner conductor (N / mm ² ),

δ ₂ - temporary tensile strength of the outer conductor (N / mm ² ),

δ ₃ - temporary tensile strength of steel wires (N / mm ² ),

d is the diameter of the wires of the outer conductor and steel wires (mm ² ).

To give the cable additional strength over the outer conductor, an additional fastening element in the form of threads is applied.

To protect the cable from moisture, water-blocking threads can be additionally laid between the cores of the external conductor.

The insulation of the inner and outer conductor can be made of polyvinyl chloride plastic compound or silanol crosslinkable polyethylene.

To increase the fire resistance of the cable, the insulation of the internal and external conductors can be made of plastic compound that does not spread combustion.

Additional differences of the proposed cable is also that the inner conductor can be made of one steel and six copper or aluminum wires, and the outer conductor can contain 4 or 6 steel wires.

An example of the design of the proposed cable with a multi-core inner conductor and an outer conductor containing 6 steel wires is presented in figure 1 and figure 2, where:

1. Inner conductor

2. Insulation of the inner conductor

3. External conductor

4. Steel wires

5. The fastening element

6. External insulating sheath

7. Water blocking thread.

In the proposed cable, the inner conductor 1 is made of copper or aluminum wires twisted together in a core. On top of the inner conductor 1, insulation 2 of the inner conductor 1 is applied from polyvinyl chloride plastic compound, or silanol-crosslinkable polyethylene, or non-flame retardant plastic compound. On top of the insulation 2 of the inner conductor 1 is an external stranded conductor 3, consisting of aluminum wires. Between the veins of the outer multicore conductor 3, water blocking strands 7 are laid. To give the cable construction strength, some of the veins of the outer and inner conductor are made of galvanized steel wires 4. A fastening element 5 in the form of threads is applied over the outer conductor 3.

For example, we perform the calculation of the number of wires for a particular cable of the AVK 6/6 brand

Where,

n is the number of steel wires

k - safety factor equal to 1.4 to 1.5, choose a coefficient equal to 1.4

P - breaking strength of the cable, (N), equal to 3021 N, according to the requirements of the PUE

S is the nominal cross section of the inner, outer conductor, (mm ² ), based on the brand of cable, its cross section is 6 mm ²

δ ₁ - temporary tensile strength of the inner conductor, (N / mm ² ), the reference value, based on the technical specifications is 162 N / mm ²

δ ₂ - temporary tensile strength of the external conductor, (N / mm ² ), the reference value, based on the technical specifications, is equal to 176 N / mm ²

δ ₃ - temporary tensile strength of steel wires, (N / mm ² ), reference value, based on the technical specifications is equal to 1800 N / mm ²

d is the diameter of the wires of the outer conductor and steel wires, (mm ² ), is selected based on the perimeter of the circumference of the insulation of the inner conductor, taking into account the need to cover the insulation of the inner conductor with wires of the outer conductor not less than 80% -90%, in this case the diameter of the wires of the outer the conductor is chosen equal to 0.5 mm.

Based on the calculated formula, we choose the closest, larger integer value, in our case it is 4. Thus, in order for the AVK 6/6 cable to meet the requirements of the PUE, it is enough to place 4 steel wires in its outer conductor.

Cable manufacturing technology consists of the following operations:

- drawing of aluminum or copper wires of the inner conductor,

- twisting of aluminum (copper) and steel wire into the core on a twisting machine,

- application by extrusion of the insulation of the inner conductor,

- the combined process of applying an external conductor with water-blocking threads using SZ-twisting with the application of a fastening thread (tape) by the method of winding and applying an external insulating sheath is performed on a combined line consisting of a reverse SZ-twisting device, a winding device and an extruder.

For the manufacture of cable the following materials are used:

- Aluminum wire of grades AM, APT, AT according to TU 16.K71 - 088

- Galvanized steel wire according to TU 14-4-1457 or GOST 1526

- Polyvinyl chloride plastic compound in accordance with GOST 5960

- Composition of silanol-crosslinked polyethylene according to TU 301-05-131.

The design of the proposed cable eliminates the possibility of unauthorized connection to a power line equipped with this cable. In addition, the proposed cable has high strength and

resistance to stretching and sagging, which makes it possible to use it on overhead power lines. Through the use of a multi-core inner conductor, the flexibility of the cable is increased compared to the prototype. The use of silanol-crosslinked polyethylene as an insulation material can reduce the weight of the cable, increase its service life, and it is also possible to operate this cable at a higher temperature. The use of non-combustible plastic compound as an insulation material increases the fire safety of cable lines equipped with a cable of the proposed design.

Claims (8)

1. Coaxial cable for transmission and distribution of electrical energy, including an inner conductor, insulation of the inner conductor, on which the outer multicore conductor of aluminum wires is concentrically applied, and an outer insulating sheath, characterized in that the inner conductor is single-core or multicore of copper or aluminum wires twisted together in a core, part of the veins of the inner and outer conductors is made of galvanized steel wires, and the number of steel wires c determined by the required breaking load, which must withstand a cable, according to the formula:

, Where n is the number of steel wires; k - safety factor equal to from 1.4 to 1.5; P - breaking strength of the cable, N; S is the nominal cross section of the inner, outer conductor, mm ^2; δ ₁ - temporary tensile strength of the inner conductor, N / mm ^2; δ ₂ - temporary tensile strength of the outer conductor, N / mm ^2; δ ₃ - temporary tensile strength of steel wires, N / mm ^2; d is the diameter of the wires of the outer conductor and steel wires, mm ² , in addition, a fastening element in the form of threads is superimposed on top of the outer conductor. 2. The cable according to claim 1, characterized in that the inner conductor is made of one steel and six copper or aluminum wires. 3. The cable according to claim 2, characterized in that the outer conductor contains 4 steel wires. 4. The cable according to claim 2, characterized in that the outer conductor contains 6 steel wires. 5. Cable according to any one of claims 1 to 4, characterized in that water-blocking threads are additionally laid between the cores of the external conductor. 6. The cable according to any one of claims 1 to 4, characterized in that the insulation of the inner and outer conductors is made of PVC compound. 7. Cable according to any one of claims 1 to 4, characterized in that the insulation of the inner and outer conductors is made of a composition of silanol-crosslinked polyethylene. 8. Cable according to any one of claims 1 to 4, characterized in that the insulation of the inner and outer conductors is made of plastic compound that does not spread combustion.