Anyone whose work is related to the electrical service, very well aware of the troubles that carries a short-circuit (short circuit).Sometimes it is considered that it is damaged.This is not true.Short circuit - is a process, or if you like, the emergency operation of any portion of the installation.But the consequences of his really lead to damage.The generally accepted definition reads: "Short circuit - is a direct connection between two or more points of the circuit having different potential.It is the abnormal (unintended) mode of operation. "
To understand what is happening in the circuit at the moment when there is a short circuit, it is necessary to recall the principles of operation of the circuit elements.Imagine a simple circuit consisting of power supply, two conductors and load (eg bulbs).Under normal circumstances, there is a conductor in the directional movement of charged elementary particles due to the constant influence of the electromotive force of the source.They move from one pole to another source via two wires and the bulb portion.Accordingly, the lamp emits light because the particles make it a specific job.
At the direction of the alternating current is constantly changing, but in this case it does not matter.The number of electrons passing through a particular portion of the chain per unit time is limited by the resistance lamp conductors source of EMF.In other words, the current does not increase indefinitely, and corresponds to the steady state.
But for some reason, damaged insulation on the circuit.For example, the lamp was flooded with water.In this case its electrical resistance decreases.As a result, the current loop current is limited by the total resistance of the power supply wires and water "isthmus" in the lamp.Typically, this amount is so insignificant that the calculations do not take into account (except for specialized computing).
The result is a virtually infinite growth of current determined by the classical Ohm's law.In this case, often mention short-circuit power.It is determined by the limiting value of the electric current which is able to give power supply to failure.By the way, it is forbidden to connect the wiring (short-circuit) contacts the opposing batteries.
Although the example we are considering the removal of the lamp circuit resistance due to the ingress of water, cause a short circuit set.For example, if we talk about the same scheme, the short-circuitIt can also occur if the insulation is broken at least one conductor and it touches the ground.In this case, the current from the power supply will follow the path of least resistance, that is, the land has a huge capacity.Damage to the insulation of two conductors and their contact will lead to the same result.
The above can be summarized: KZ may be with or without land.In the processes are not affected.
Which the damage referred to in the beginning of the article?As is known, the higher the current flowing through the circuit sections, the more heat.With sufficient power source during short circuitSome sites simply burn out circuit, turning to copper dust (copper elements).
Protection against short-circuit is quite simple and effective.Reports of destruction because of the closure occurs mainly due to incorrect parameters selected protection devices, incorrect selectivity.When it comes to household circuit 220, the circuit breakers are used.In them the excessive increase in current solenoid release, located inside the chain breaks.
