Rules for the operation of electrical wiring. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Electrician

Rules for the operation of electrical wiring. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Electric installation work

Network congestion lead to heating of wires and cables above the permissible temperature for them under the conditions of safety and reliability. For wires and cables with rubber and plastic insulation, the PUE sets the highest permissible heating temperature of +65 °C under long-term current load. Permissible current loads depend on the cross-section of the conductor, its design, cooling conditions and installation method.

When there are overloads in the network, the insulation of the conductors ages: the rubber dries out, cracks and crumbles, the plastic insulation and sheath melts and softens, the paper braid becomes charred, etc. Weakening of the insulation over time leads to short circuits between the current-carrying conductors.

Short circuits can also be caused by faulty switches, plug sockets, unreliable connections in branch boxes, mechanical damage to the wire as a result of careless handling, malfunction of household electrical appliances that do not have protection, etc.

To protect electrical wiring during abnormal conditions are used protection devices that automatically turn off the electrical circuit if damaged, - plug fuses, automatic threaded fuses (PAR) and automatic switches (automatic circuit breakers).

All electrical wiring elements - installation products, wires, cables, protection devices, etc. - are designed for a long service life, but over time they wear out, age and fail. Therefore, electrical wiring and its elements must be periodically inspected and checked: at least once every 1 years in rooms with a normal environment and once a year in others. Detected malfunctions must be corrected immediately.

Malfunctions and damage to electrical wiring and its elements can occur due to careless handling, poor-quality installation work, or physical wear and tear of wires and cables as a result of long service life.

Switches that have broken spring contact plates or metal-ceramic contacts or cracked covers cannot be repaired and should be replaced immediately.

In plug sockets, over time, the springs that compress the contact sockets weaken, as a result of which the plug connection heats up, and the contacts become covered with soot and melt. To ensure reliable operation of the plug connection, it is necessary to replace the springs and ensure contact in which the pins of the plugs are firmly held in the sockets of the socket. If spare compression springs are not available, the sockets must be replaced. This must also be done if there are cracks and chips in the base and lid.

Sometimes, when you pull a plug from a hidden socket, the entire socket and wires fall out. You can't leave it like this.

You should also not try to insert the socket into the box without turning off the power - this can lead to injury. When securing the socket in the box, you must ensure that the wires do not get under the spacer tabs. The screws for securing the legs must be screwed in alternately and evenly. In addition, when removing the plug from the socket, you must hold the socket cover with your other hand. This will prevent the outlet from becoming loose in the box or support base.

When inspecting apartment panels, it is necessary to monitor the condition of the contacts at the places where the wires are connected. An unreliable connection leads to heating and burning of contacts, destruction of insulation and subsequent sparking. Such contacts must be promptly cleared of soot and metal deposits and tightened tightly. Circuit breakers and fuse links must match the loads and cross-sections of wires and cables. There should be no traces of oxide, dirt, or dust on the contact surfaces of the fuses.

Protection devices with damaged housings or failure to operate cannot be repaired; they must be replaced.

Apartment units with cabinets must have working locks and reliable door seals. It is not permitted to store foreign objects in these cabinets. Electric meters must not have damage to the housing, sight glasses, terminal covers, etc. Cabinets, protection devices and all accessible places must be regularly cleaned of dust and dirt.

When inspecting internal electrical wiring, the tension and fastening of wires and cables are checked. Loose and loose wires and cables must be tightened and securely fastened. Damaged rollers, insulators, insulating tubes, porcelain funnels and bushings. Damaged sections of wiring are replaced immediately. In this case, the work is carried out in accordance with the norms and rules for this type of wiring and installation method. As a rule, damaged wiring is replaced in the area from the nearest branch in the box or insulating support to the place of damage. The newly laid wire is connected at the same points of the electrical wiring where the connections were before the repair.

When inspecting external electrical wiring and inputs of branches from the overhead line, check for burns, chips and cracks on the insulators; breaks and melting of wire cores, integrity of connections, condition of connections; tension of wires and compliance with the PUE of the distances between them, wires and ground, wires and building structures; condition of supports; Do the branches of trees located near the wires pose a danger?

Produced at least once every 1 years network isolation test megohmmeter with a voltage of 500 or 1000 V. The insulation resistance is measured between each wire and ground, as well as between every two wires when the network is disconnected. When measuring insulation resistance, the lamps must be unscrewed and the switches turned on. The lowest insulation resistance is 0,5 mOhm.

When checking the insulation resistance, you need to pay attention to the integrity and serviceability of the grounding wires. If the insulation resistance of the wires is less than 0,5 mOhm, it is necessary to determine the cause and correct the damaged section or element of the wiring.

When checking the electrical wiring, the need for major repairs is determined. general technical condition wires and cables, fasteners, etc. The main indicators are:

1) insulation resistance of wires and cables is less than 0,5 mOhm and current leakage is more than 20 mA;

2) low mechanical strength of the insulation of current-carrying conductors (drying, cracking, shedding, fragility);

3) overheating of wires, cables and connections under network loads close to the nominal ones.

Work related to the inspection of electrical wiring and electrical installations and their repair must be carried out in strict compliance with safety regulations.

Author: Bannikov E.A.

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