The simple way to prevent fire from electric shock is not well known

In the past, many fires of houses, factories and warehouses occurred, causing great losses of people and property. In particular, most causes of fire and explosion related to electrical equipment system.

In the framework of this article, the author only focuses on the cause of fire due to overload or short-circuiting.

Currently, in every household, factory, after electricity meter, the power departments are equipped with appropriate protection switches . This protection switch is often called a CB (English: circuit breaker) . There are also places called it automatic breaker, automatic fuse.

An unsafe electrical outlet may also lead to fire or explosion.

Automatic fuses are responsible for isolating electrical equipment such as lamps, fans, electric cookers, water heaters, electric motors . or part of the electrical system from the grid when an overload or short-circuit case occurs. or there is electrical leakage. Here we focus two cases of fire and overload. A modern protection switch has the function of protecting when there is overload and short circuit for power transmission lines and electrical equipment, electrical systems.

Overload: The protective switch is equipped with a thermoelectric breaker, which is a bimetallic set with two metal leaves with different expansion coefficient. The electric current of electrical appliances (electric stoves, air-conditioners .) runs through a heating wire that heats the bimetal bar, the bimetallic rod is bent because of heat. When the curvature is greater than the norm (for a predetermined current intensity, for example 16A), the bimetal bar activates the breaker.

Thermal breaker with thermal power has a delay time. The bimetallic rod only activates the breaker when the current through the load exceeds 3 to 5 times the rated current of the automatic type B fuse. C or D type automatic fuses even require large currents 5-10 times, 10-20 times the rated current.

Automatic thermal shut-off fuses only protect devices for overload and not for short circuits.

For example, an electric stove is connected to a power source with a double wire. Electric current not only heats the electric stove but also the electric wire Because the subjective user does not care about the type of power line, section, resistor wire .

A large amount of electricity is used to heat the stove, and the insulation is melted gradually and broken. At some point, because the insulating plastic is broken and electrified, it is shorted between two electrical wires. In this case, if the user of the electric stove uses CB (protection switch) with only overload protection function, when the electric power is shorted, the CB has not interrupted the power yet, the whole power line has flowed out because of short-circuiting. Electricity and heat will cause a fire.

A similar situation will occur if the homeowner uses an old fuse or even fuses because of a break many times and is connected by a 'super durable' electric wire!

Short circuit (short-circuit): In addition to the thermal power breaker with bimetallic, a CB or modern automatic fuse also has an electromagnetic breaker.

When there is a short circuit or an electrical connection between two electrical wires, a large current flows through a coil that creates a magnetic field strong enough to pull on an iron core in the coil that activates the breaker. This process evolves very quickly, almost immediately (about 0.01 seconds).

Electromagnetic breaker structure.

Thanks to such a fast shutdown, electrical wires and electrical equipment are not burnt, causing a fire. Automatic fuse (CB) with electromagnetic breaker structure can only be switched on after the cause of the shutdown, electric touch is corrected.

A modern automatic fuse for civil use includes both thermal (bimetallic) and electromagnetic. Both of these devices are connected in series, so only one of these mechanisms is activated, immediately the electrical device is isolated from the grid.

Therefore, in order to avoid fires due to electric shocks, we should buy and use modern CBs and auto fuses with electromagnetic interrupt function. Although more expensive than automatic fuses with only a thermal breaker, it meets safety when there is a short-circuit or short-circuit.

Automatic fuse (CB) has an electromagnetic breaker mechanism.

In addition, to avoid the maximum of fires due to short-circuit, short circuits in people's homes, enterprises, power departments, and fire protection authorities should regulate and check the automatic fuses. there is an electromagnetic breaker to ensure safety even if there is a short-circuit, short-circuit connection. Need to eliminate or prohibit the use of unsafe fuses, automatic fuses only overload protection, no quick breaker by electromagnetic when there is short circuit, short circuit.