How to prevent fires in wires and cables due to wire overload?

During the operation of the wire, it will generate heat due to the presence of resistance. The resistance of a wire is generally very small, and its heating power can be expressed by the formula q=I ^ 2R. Q=I ^ 2R indicates that for a section of wire in actual use (where R is essentially constant), the greater the current passing through the wire, the greater its heating power; If the current is constant, the heating power of the wire is also constant. The heat released during operation will be absorbed by the wire itself, causing an increase in wire temperature. Although the wire continuously absorbs the heat released by the current during operation, its temperature does not rise indefinitely. Because while the wire absorbs heat, it also continuously releases heat to the outside world. The fact shows that the temperature of the wire gradually increases after being electrified, and then remains constant at a certain point. At this constant point, the power of the wire's heat absorption and release is consistent, and the wire is in a state of thermal equilibrium. The ability of wires to withstand high temperature operation is limited, and exceeding a certain high temperature operation can pose a danger. This high temperature naturally corresponds to a certain high current, and the operation of the wire beyond this high current is considered overload. Overloading of the wire directly leads to an increase in temperature of the wire itself and nearby objects. The increase in temperature is the direct cause of this type of fire.

Overload causes damage to the insulation layer between double stranded wires, leading to short circuits, burning of equipment, and causing fires. Double stranded wires are separated by an insulation layer between them. Overloading causes the insulation layer to soften and break, resulting in direct contact between the two wires causing a short circuit and equipment damage. At the same time, the high temperature generated by the large current during the short circuit caused the circuit to catch fire and melt, and the resulting molten beads fell onto combustible materials, causing a fire. Overloaded temperature rise can directly ignite nearby combustibles. Overloaded wires transfer heat, causing an increase in the temperature of nearby combustibles. For combustibles with lower ignition points nearby, it is possible to ignite them and cause a fire. This danger is particularly prominent in warehouses storing flammable materials and buildings with easy to use and flammable decorations.

Overload also puts the connections in the circuit under overheated conditions, which accelerates its oxidation process. Oxidation produces a thin layer of non-conductive oxide film at the connection point, which increases the resistance between the contact points and causes phenomena such as ignition, leading to fires.

So, how to prevent fires caused by wire overload?

1. In the process of line design, the capacity of the site should be accurately determined, and the possibility of adding new capacity in the future should be fully considered to select suitable types of wires. Large capacity, thicker wires should be selected. Line design and reasonable selection are key steps in preventing overload. If the design selection is improper, it will leave inherent hidden dangers that are difficult to rectify. Some small-scale projects and places are not carefully designed and selected. Choosing and laying lines arbitrarily is very dangerous. New electrical appliances and equipment should fully consider the load-bearing capacity of the existing lines. The original line did not meet the requirements and should be redesigned and renovated.

2. The line should be constructed and laid by qualified electricians in accordance with relevant specifications. The laying conditions of the circuit directly affect the heat dissipation of the wires. Generally speaking, the laying of power lines should not pass through flammable or combustible materials or stacks, as this can lead to poor heat dissipation of the wires, heat accumulation, and the possibility of igniting surrounding flammable materials, increasing the risk of fire caused by overload; The wiring inside the suspended ceiling of public entertainment venues should be protected by steel pipes to separate the ceiling from the wiring. Even if there are molten beads in overload, short circuit, and other situations, they will not fall off, avoiding the occurrence of fires.

3. Strengthen electricity management, avoid disorderly wiring and tying, and use mobile sockets with caution. Disorderly wiring, misconnecting, and using mobile sockets are actually adding electrical devices to a certain section of the line, increasing the current and potentially causing overload. Mobile sockets have significantly more sockets than fixed sockets on the wall. If too many electrical devices are used on mobile sockets, the original wiring will inevitably be unable to withstand them. For high-power equipment and appliances, separate circuits should be installed, and mobile sockets should not be used as wiring sources.

4. Accelerate the renovation of old railway lines and eliminate fire hazards. Old enterprises, old residential areas and other units, due to their long service life, many lines have aged and exceeded their service life. Even if the current carrying capacity of some lines is not large, aging lines cannot withstand such a current carrying capacity and also have the danger of overload. Especially in old residential areas, the power lines have long aged, but with the improvement of people's living standards and the increase of household appliances, their electricity consumption is still increasing year by year, which is really adding insult to injury. For old lines, timely supervision and coordination should be carried out to urge their rectification as soon as possible, in order to eliminate hidden dangers.