Any person whose work is related to the maintenance of electrical equipment knows very well about the troubles that a short circuit carries (short circuit). It is sometimes considered to constitute damage. This is not true. A short circuit is a process, or, if you like, an emergency operation of a section of an electrical installation. But the consequences of it really lead to damage. The generally accepted definition is: “Short circuit is the direct connection of two or more points of an electrical circuit with different potentials. It is an abnormal (unforeseen) mode of operation. "
To understand what exactly happens in the circuit at the moment when a short circuit occurs there, it is necessary to recall the principles of functioning of the circuit elements. Imagine a simple circuit consisting of a power source, two conductors and a load (for example, a light bulb). Under ordinary conditions, in the conductor there is directed movement of charged elementary particles due to the constant action of the electromotive force of the source. They move from one source pole to another through two sections of wire and a lamp. Accordingly, the lamp emits light, since the particles do a certain job in it.
With alternating current, the direction of movement is constantly changing, but in this case it is not important. The number of electrons passing through a certain section of the circuit per unit of time is limited by the resistance of the lamp, conductors, emf source. In other words, the current does not grow indefinitely, but corresponds to the steady state.
But for some reason, the insulation in the circuit section is damaged. For example, a lamp was flooded with water. In this case, its electrical resistance decreases. As a result, the current flowing along the circuit is limited by the total resistance of the power source, wires, and the water "isthmus" on the lamp. Usually this amount is so insignificant that it is not taken into account in the calculations (the exception is specialized calculations).
The result is an almost infinite increase in current, determined by Ohm's classical law. In this case, short-circuit power is often referred to. It is determined by the limiting value of the electric current, which the power source can supply before failure. By the way, that is why it is forbidden to connect the opposite battery contacts with a wiring (short-circuit).
Although in the example we are considering eliminating the lamp resistance from the circuit due to the ingress of water, there are many reasons for short circuiting. For example, if we talk about the same scheme, then short circuit It can also occur if the insulation of at least one wire is broken and it touches the ground. In this case, the current from the power source will follow the path of least resistance, that is, to the ground, which has a huge capacity. Damage to the insulation of two wires at once and their contact will lead to the same result.
The foregoing can be summarized: short-cuts can be with and without land. This does not affect ongoing processes.
What kind of damage was discussed at the beginning of the article? As you know, the higher the value of the current flowing through the sections of the circuit, the greater their heating. With sufficient source power at short circuit some parts of the chain simply burn out, turning into copper dust (for copper elements).
Short circuit protection is quite simple and effective. Messages about damage due to a fault arise, first of all, due to incorrectly selected parameters of the protection devices, incorrect selectivity. If we are talking about a household circuit 220 V, then use circuit breakers. In them, with an excessive increase in current, the electromagnetic release located inside breaks the circuit.