Installation of grounding devices (earthing installation). Grounding device

Grounding device

Defense land — this is the intentional grounding of metal parts of an electrical installation that are not under voltage (disconnector handles, transformer housings, support insulator flanges, transformer equipment housings, etc.).

Installation of grounding devices consists of the following operations: installation of grounding conductors, laying of grounding conductors, connecting grounding conductors to each other, connecting grounding conductors to grounding conductors and electrical equipment.

Vertical earthing rods of angle steel and rejected pipes are sunk into the ground by driving or recessing, round steel by screwing or recessing. These works are carried out with the help of mechanisms and devices, for example: a pilot (driving into the ground), a drilling device (screwing electrodes into the ground), PZD-12 mechanism (screwing grounding electrodes into the ground).

For the grounding device, the most common are electric deep drills, which have a standard electric drill and a gearbox that reduces the speed below 100 revolutions per minute and accordingly increases the torque of the screw electrode. When these deepeners are used, a bit is welded to the end of the electrode, which loosens the soil and makes it easier to sink the electrode. The commercially available tip is a 16 mm wide steel strip, tapered at the end and spirally curved. Other types of electrode tips are also used in installation practice.

When grounding, vertical grounding should be placed at a depth of 0.5 — 0.6 m from the level of the ground layout and protrude from the bottom of the trench by 0.1 — 0.2 m. The distance between the electrodes is 2.5 — 3 m. Horizontal ground electrodes and connecting strips between vertical ground electrodes laid in trenches with a depth of 0.6 — 0.7 m from the level of the ground layout.

All connections in the ground circuits are made by overlapping welding; welding points are coated with bitumen to avoid corrosion. A trench 0.5 m wide and 0.7 m deep is usually dug. electrical project.

Entrances to the building of grounding wires performed in at least two places. After the installation of grounded electrodes, an act of hidden work is drawn up, indicating in the drawings the connection of the grounding devices to stationary landmarks.

Grounding of trunk wires laid on the walls at a distance of 0.5-0.10 m from surfaces at a height of 0.4-0.6 m from the floor level. The distance between the attachment points is 0.6-1.0 m.In dry rooms and in the absence of a chemically active environment, it is allowed to place grounding wires near the wall.

Grounding strips, they are attached to the walls with dowels, which are fired with a construction and installation gun either directly to the wall or through intermediate parts. Built-in parts to which ground strips are welded are also widely used. With a PC-type gun, you can shoot parts of steel sheet or strip up to 6 mm thick into foundations of concrete (up to 400 grades), bricks, etc.

In humid, especially humid rooms and indoors with caustic vapors (with an aggressive environment) grounding wires welded to supports fixed with dowels-nails. To create a gap between the grounding wire and the foundation in such premises, a stamped holder made of strip steel with a width of 25-30 mm and a thickness of 4 mm is used, as well as a clamp for laying round earthing conductors with a diameter of 12-19 mm. The length of the weld lap should be twice the strip width for rectangular strips or six diameters for round steel.

The ground wires are connected to the pipelines, if there are valves or bolted flange connections on the pipes, bypass jumpers are made.

Parts of electrical installations that must be grounded are connected to the grounding network with separate branches. Steel wire for grounding and attached to metal structures by welding, to equipment — possibly by welding. ground bolt or, when the conductors are connected to copper conductors by wire wrapping and soldering. Usually, a common earth loop is made around the substation, to which the ground wires from inside the substation are welded.Individual items of electrical equipment connected to ground wires in parallel, not in series, otherwise, if the ground wire is broken, part of the equipment may be ungrounded.

At substations, all elements of electrical equipment and metal structures are grounded. Power transformers are earthed flexible steel cable jumper. On the one hand, the jumper is welded to the ground wire, on the other hand, it is connected to the transformer by a bolted connection. The disconnectors are grounded through the frame, drive plate and thrust bearing; housing for auxiliary contacts — by connecting to a ground bus.

If disconnectors and drives are mounted on metal structures, then grounding is done by welding a grounder to them.

Earth protectors 6 — 10 kV by connecting the earth wire to the insulator flanges of the posts, frame or metal structure on which they are mounted.