Household appliances have brought many conveniences to people’s daily life, let us make better use of the limited time, but the loss caused by the fire caused by household appliances is also immeasurable. Therefore, this article will talk about the knowledge of household electricity fire protection, please take the time to come in and have a look!
I. what is overload? What is the cause of overload? How to carry out overload protection?
The amount of current in an electrical circuit that allows continuous passage without overheating the wire is called safe current carrying capacity or safe current. If the current flowing through the conductor exceeds the safe carrying capacity, it is called conductor overload. Generally, the maximum allowable working temperature of conductor is 65 ° C. In case of overload, if the temperature exceeds this temperature, the insulation will age rapidly and even the circuit will burn.
The main causes of overload are improper selection of conductor cross section, the actual load has exceeded the safe current of conductor, and “small horse pulling cart” phenomenon, that is, too many high-power equipment has been connected in the line, which has exceeded the load capacity of distribution line.
Overload protection shall be taken for lighting lines in important material warehouses, residential areas and public buildings, power lines that may cause long-term overload of wires or cables, as well as insulated wires with flame retardant sheath laid on combustible or refractory building components. The overload protection of the line should adopt the automatic switch. During operation, the setting current of the long-time delay action of the automatic switch shall not be greater than the long-term allowable load current of the line. If the fuse is used for overload protection, the rated current of fuse melt shall not be greater than the long-term load current of the line. When the automatic switch is used as the protection device, its current release shall be installed on the phase line in the three-phase four wire system with neutral point grounded; in the three-phase four wire system without neutral point grounded, it is allowed to be installed on the two-phase; in the two-phase two wire system without neutral point grounded, it is allowed to be installed on the one phase.
What is leakage? How can leakage cause fire? How to prevent leakage?
The so-called leakage is that the insulation of the wire is lowered in a certain place of the line due to some reasons (wind, rain, sun, moisture, pressure, scratch, friction, corrosion, etc.), resulting in the passage of part of the current between the line and the line, between the line and the ground.
When the leakage current flows into the ground, in case of parts with high resistance (such as the connection part of reinforcement), local high temperature will be generated, which will cause the nearby combustible to catch fire and cause fire.
In order to prevent electric leakage, first of all, it is necessary to make an article on the design and installation. The insulation strength of the conductor and cable shall not be lower than the rated voltage of the network, and the insulator shall be selected according to the different voltage of the power supply. Secondly, in humid, high-temperature and corrosive places, it is strictly prohibited to lay the insulated conductor on the surface, and the bushing shall be used for wiring; in dusty places, the line shall be cleaned frequently. The third is to try to avoid damage during construction and pay attention to the quality of conductor connection; the mobile lines of movable electrical equipment are protected by aluminum sleeve, and the places often under pressure are concealed with steel pipes. The fourth is to install the leakage protector and check the insulation of the line frequently.
What is short circuit? What are the main causes of short circuit? How to prevent short circuit fire?
On the electric circuit, the phenomenon that the current suddenly increases due to various reasons is called short circuit. The contact between phase lines is called the same short circuit; the contact between phase line and ground wire, with grounding conductor or directly with the ground is called the short circuit to ground. When the short-circuit current suddenly increases, its instantaneous heat release is very large, which greatly exceeds the heat output of the normal operation of the line. It can not only burn the insulation, but also melt the metal, causing the combustion of combustible materials and fire.
The main causes of the short circuit are: 1. The line is aging and the insulation is damaged, resulting in the short circuit; 2. The power supply is over-voltage, resulting in the insulation breakdown; 3. Small animals (such as snakes, rabbits, cats, etc.) are connected to the bare wire across; 4. A variety of artificial random connection; 5. The outdoor overhead line is loose and collided under the action of strong wind; 6. The line is installed too low and various transport or metal objects Short circuit caused by collision.
We hereby remind the public to pay attention to the aging of household appliances, regularly check and maintain them, and prevent the appliances from being live for a long time, far away from fire accidents and electric shock accidents. The common sense of children’s home electric shock prevention is still in the process of updating, please continue to pay attention to this website!