Earthing of the cable armor according to PUE: elements of the main line included in the circuit, the product in the ground and the channel

In accordance with the rules for electrical installations (PUE) for cable armor, grounding is mandatory. The contour includes other component parts of the product and supporting structures. The regulations for the implementation of protective measures in relation to main power pipelines established by the regulatory document are aimed at the stability of the power supply. There are differences in performance between the protection of armor in the cable duct, room and ground.

Earthed elements of the trunk line

Coating of insulated cores with metal sheaths and steel strips is carried out in order to protect transmission means against mechanical damage, exposure to moisture, temperature and ultraviolet radiation. The rules prescribe to ground all live parts of cable electric lines (CEL). The brands of armored products contain the letters in the encrypted name: B - protection made of steel tape (AVBbShv, AAB2l); K - from a round wire of an alloy of iron with carbon (PvKShp, ASKl); P - from flat wire rod of the same material (AAPL).

Some protected cables are made in a different version - instead of steel armor, they are covered with an aluminum or lead sheath (AAShv, ASShv). Such a product with a modified design is inferior in strength, but more resistant to aggressive environments and corrosion. Also, the cables are equipped with a shielding layer against electromagnetic radiation and for static potential equalization. Braiding material - aluminum wire or foil. Subject to grounding:

• metal sheath of the group of power conductors, armor and screen of the control cord;
• docking sleeve when splicing products of building length;
• conductive structures of KEL: gallery, tray, box;
• line supporting cable;
• a metal pipe that serves as a channel for an armored cable in the room.

Protected KELs must have a ground loop according to the PUE on both sides of the line. This requirement applies to branches longer than 200 m.

Earthing switches for cable armor in the ground

Laying main lines of power supply in the ground depends on the properties and composition of the uncovered soil layer.

In areas of permafrost, in places with rocky and unstable soil, a cable with wire armor is laid, in a pliable stable ground - made of steel tape. Before placing the line in the trench, it is necessary to inspect the product along its entire length for the integrity of the shell. The current protection of the armor is carried out with a flexible uninsulated wire.

The table shows the ratio of the cross-sections of the cable cores (top line) and the ground electrode (mm²):

< 10	16―35	50, 70, 95, 120	150―240
6	10	16	25

If a private house is required to be connected to the power grid, then the CEL can be laid not only in the ground, but also through the air. In each of these cases, protection of the trunk is required from two sides. With her device adhere to the following rules:

1. The contact at the point of connection of the grounding wire to the armored cable is provided using a special clip (clip), bolts or soldering. In the latter case, the contact planes are pre-cleaned and tinned. Attach protection to the top steel strap, and in the case of wire armor, to all wire rods around the circumference.
2. The outer shell of the KEL does not allow damage along the entire length of the line. If it is necessary to carry out repairs or when connecting the segments for splicing, use a special coupling. To close the circuit, it is attached to the armor on each side with a stranded copper wire. The adapter kit includes waterproofing and connecting elements: earthing switch, lugs with shear screws and clamps.
3. The ends of the armored cable are cut carefully, taking care not to damage the protective sheath. The upper braid is removed to a greater length than the inner one. In order to prepare the connection correctly, use a special template, which is offered by cable manufacturers.

To ensure the safety of the ground loop, there should be no roots of trees and shrubs in the places where the CEL is laid. When the highway crosses high-risk communications (roads and construction sites), additional security measures are taken. To do this, use sand bedding and arrange cable channels. In such cases, wire braiding is preferable. In addition, there are options for laying CELs in rooms and on various structures.

Binding to the ground of the duct cable

Structures designed for laying power supply lines include double floors, overpasses and tunnels, ducts and canals. Both the cable armor and the metal parts of the supporting structures are grounded. Mandatory conditions:

1. It is allowed to attach tapes or wire braids to steel trays, you can connect to iron supports and contours of buildings and structures going into the ground, using them as grounding contour.
2. Inside rooms finished with flammable materials, it is not allowed to lay KELs directly to the surface on raw concrete. To hang the armored cable, brackets are installed that provide a distance from the wall of ≥50 mm. Another option is to place the line in a metal channel or iron gutter.
3. The entry of the main line into housing construction is usually carried out through the foundation, equipping the passage with a plastic or steel pipe with an inner diameter twice the size of the cable. The armor is grounded on both sides - near the shield and on the near support. There should be no connections in this interval. You can also bring the CEL into the building through the opening in the wall.

A prerequisite for laying the highway along building structures is the ability to freely access any point of the line for external inspection and in case of repairs.

Fulfillment of all the above recommendations will eliminate the likelihood of power outages, fires and electric shock to a person.