Seven components of electrical system installation engineering

1. Power distribution engineering

Substation distribution engineering is the construction process of inspecting and installing the substation distribution equipment in the substation distribution system.

Substation equipment is a general term for substation equipment. Its main function is to change voltage and distribute electrical energy. It is composed of transformers, circuit breakers, switches, transformers, reactors, capacitors and high and low voltage distribution cabinets.

Installation of substations and distribution equipment is divided into three types: indoor, outdoor and pole type, usually installed indoors (substation or substation).

(1) Transformer installation

① Transformer treatment method: a single weight of less than 10 tons of transformers are usually handled by cars and cranes.

② Transformer inspection: Usually, the truck crane or chain crane is used to check the core and cover.

(3) Transformer drying: The length of transformer drying time depends on the humidity of the transformer and the selected drying process. Transformer drying methods include short-circuit drying and eddy current drying.

(2) Mechanical structures are usually used for the transport and installation of circuit breakers, isolation switches, load switches, reactors, capacitors and high voltage distribution cabinets.

2, bus, insulator

(1) Bus bar

It is used in places with high current and is divided into hard bus and soft bus. The hard bus is also called the bus, and the soft bus includes the combined bus.

According to the material, the bus can be divided into three types: copper bus, aluminum bus and steel bus.

According to the shape of the bus, it can be divided into ribbon, trough, closed and heavy.

(2) Insulator

The main function is to insulate and fix the bus and wire. It can be divided into indoor and outdoor, as well as hanging string insulators. Indoor insulators have 1 to 4 holes, and outdoor insulators have 1 hole, 2 holes, and 4 holes.

Insulators are usually installed on high and low voltage switchgear, bus bridge, wall or bracket.

① Low voltage pin insulator. Overhead wires below 500V are used to insulate and hold conductors.

② Low voltage butterfly porcelain insulator. Terminals, stretch rods and corner rods for overhead wires below 500V, as insulated wires and fixed wires.

③ Terminal (wire nose). There are two kinds of copper and aluminum.

3, control equipment and low-voltage electrical appliances

Electrical control equipment is mainly the installation of low-voltage panels (screens), cabinets and boxes, as well as the installation of various types of switches, low-voltage appliances, cabinets, wiring, terminals and other commonly used control equipment and low-voltage appliances in power and lighting projects.

Distribution box (panel) can be divided into two types according to different uses: distribution box (panel) and lighting distribution box (panel). According to the installation method, it can be divided into surface mounting (hanging) and hidden (embedded) and semi-bright and semi-dark. According to the production material, can be divided into iron, wood and plastic products. Iron distribution boxes are mainly used on site.

Distribution boxes (panels) are divided into stereotyped products (standard distribution boxes and panels), special-shaped complete sets of distribution boxes (non-standard distribution boxes and panels) and on-site distribution boxes (panels). The standard distribution box (panel) is factory assembled; Non-standard distribution boxes (panels) are customized or manufactured according to design or actual needs. If the design is a non-standard distribution box (panel), it is usually necessary to use the designed distribution system diagram, which is processed by the factory.

(1) Distribution box

In the past, distribution boxes were called distribution boxes. Because the name of the latter is not very accurate, it is collectively called the distribution box in various newly developed national standards and specifications.

There are many types of distribution boxes, XL-3, XL-4, XL-10, XL-11, XL-12, XL-14 and XL-15 are all old products and are still in use. Production and use

(2) Lighting distribution box

The lighting distribution box is suitable for industrial and civil buildings in lighting as well as small power control circuits with AC 50Hz and rated voltage below 500V for overload, short circuit protection and normal conversion of circuits.

Because the country only approves the unified technical standards of the lighting distribution box, but does not carry out a unified design, there are many domestic manufacturers, and there are many specifications and models. When selecting a standard lighting distribution box, consult the relevant product catalogues and electrical design manuals and other books.

4. Motor

Motor is a general term for generator and motor, and the motor in the construction project refers to the motor. There are many types of motors, which can be divided into DC motors and AC motors according to the different power sources.

Dc motors are mainly used in production machinery that requires high speed regulation or large starting torque.

Ac motor is widely used, according to the different power supply, divided into single-phase motor and three-phase motor.

Synchronous motor is mainly used to drive high power or constant speed machinery. Asynchronous motors are divided into squirrel cage type and winding type according to their structure.

According to the specifications, the motor must be inspected after installation to test for insulation. If the insulation is low or substandard, the motor must be dried.

5. Cable laying

According to the function and use, the cable can be divided into power cable, control cable, communication cable and so on. Cable classification is shown in Table 1. Depending on the voltage, it can be divided into 500V, 1000V, 6000V, 10000V, and higher voltage power lines.

Power cables are used to transmit and distribute high power. Control cables are used to transmit working current in distribution equipment, connect electrical instruments, relay protection and control automatic circuits

The cable laying method is as follows:

(1) Buried type

The laying method of laying the cable directly in the ground is called buried laying. Cables laid underground must be armored and protected by anti-corrosion layers, and bare cables are not allowed to be laid underground. Usually, the depth of the cable trough does not exceed 0.9m, and the laying of the floor also needs to be polished and covered with bricks or protective panels.

The steps for laying cables underground are as follows:

Measurement diagram - Digging cable trench - laying sand - laying cable - covering sand - covering brick or protective plate - filling soil - fixing pile.

(2) Place the cable along the support

The cable is usually placed along the bracket in the workshop, workshop and cable trench, and the cable is fixed to the installed bracket with clamps. The horizontal distance between the power cable brackets is 1m, and the horizontal distance between the control cables is 0.8m. Power cables and control cables can usually be placed in the same trench. The cable is usually placed vertically. The clamping distance of the power cable is 1.5m, and the clamping distance of the control cable is 1.8m.

(3) Pass the cable through the protective tube

Place the protective tube in advance, and then pass the cable through the protective tube. The inner diameter of the pipe should not be less than 1.5 times the outer diameter of the cable. Steel pipes are usually used as protective pipes. Single-core cables are not allowed to be laid through steel pipes.

(4) Laying cable bridge

A cable tray is a frame for setting up cables, which are sent from the distribution room or control room to the electrical equipment through the cable tray.

The advantage of cable tray is that it is manufactured and serialized by the factory, the quality is easy to control, the installation is convenient, and the installed cable tray and bracket are neat and beautiful.

The cable bridge is composed of a tray, a straight section of the ladder, elbows, accessories, supports and hangers. It is a general term for continuous rigid structural systems used to support cables.

6. Lightning protection grounding device

The lightning protection grounding device is composed of a grounding pole, a grounding bus, a grounding jumper, a lightning rod, a lightning rod and a lightning protection net.

(1) Grounding electrode

The ground electrode is made of steel pipe, Angle steel, round steel, copper plate or steel plate, the general length is 2.5m, and each group has 3 to 6 roots. It penetrates directly into the ground and connects to the outdoor ground bus.

(2) Ground bus

Ground bus laying is divided into indoor and outdoor. Indoor ground bus bars are usually placed along the wall clamp. The outdoor ground bus is usually buried underground. The earthwork height of the trench is 0.5m per meter long, the bottom is 0.4m, the depth is 0.75m, 0.34m3. Most ground busbars use flat or round steel as the grounding material.

(3) Ground jumper

Ground jumper refers to the connection wire when the ground bus meets obstacles to be crossed (such as building expansion joints and settlement joints), or the connection wire that needs to be welded when metal components are used as ground wires. Most tall buildings use aluminum Windows. To prevent side lightning strikes from damaging the building or injuring the human body, the ground cable must be connected to the main ribs of the wall or column according to the specifications.

(4) Lightning rod

A lightning rod is a device that receives lightning and is installed at the highest points of buildings and structures. Important places such as substations are equipped with independent lightning rods. Lightning rod is made of steel pipe and round steel.

(5) Lightning protection causes offline

A lightning rod down line is a wire that extends from a lightning rod or roof lightning net down along buildings, structures, and metal components. Usually, flat or round steel is used as the lead line.

At present, most buildings are designed to use the two main ribs in the building column as the downline and welded with the basic steel mesh to form a larger grounding network.

(6) Lightning protection net

The lightning protection net is set on the top of the building. Circular steel is usually used as a lightning protection net, and some buildings use stainless steel as a lightning protection net, which is relatively expensive. According to the code requirements, high-rise buildings are set up with a balance ring every three floors. The balance ring can be used as a balance ring in a ring beam using a ring beam reinforcement or another flat or round steel. Cause damage.

7. Pipeline wiring

Piping refers to the installation of power and control lines from the switchboard (box) to each appliance. Usually, there are two methods of open pipe and dark pipe.

Open piping is the use of fixed clamps to fix pipes to walls, columns, beams, roofs and steel structures.

Hidden pipes need to be pre-laid in walls, roofs, beams and columns with civil buildings. The advantage of dark pipes is that they do not affect the appearance and have a long service life. At present, there are three commonly used electrical pipe materials: welded steel pipe, wire pipe and PVC plastic pipe.

Dark electrical piping should be laid along the nearest line, and bending should be reduced. Tube welding is recommended because underground pipes cannot be connected. Welding of open pipes is not allowed, only wire joints can be used.