Malfunctions in the mains are a common cause of damage to electrical appliances. One of the common negative phenomena is a short circuit. It is dangerous not only for equipment, but also for the house itself, as it can lead to fire. It is possible to fight short circuit with the help of fuses and circuit breakers in the active circuit. But in the case of a de-energized wire or device, the search for a circuit is complicated. There are different ways to detect and fix a network defect.
Short circuit causes
The main factor causing a short circuit is a sharp increase in amperage. It is accompanied by a decrease in electrical wiring resistance and leads to an increase in temperature above a normal value. This leads to the possibility of ignition of flammable materials.
Why a short circuit occurs:
- Depreciation of the power supply. Over time, the insulation wears out, part of the wire is exposed, and a short circuit may occur in this area.
- Moisture. Liquid spillage on the anti-twist tape can occur during flooding. This leads to peeling off the sticky side of the tape and exposing the joint.
- Mechanical impact on insulation. During repairs, you may accidentally drive a nail into the cable routing area and damage the protective layer. Also, rodents can gnaw wires.
- Power overload for a long time. Leads to melting insulation.
- Wrong choice of circuit breaker rating. The protection device may not react and skip surges, which increases the risk of a short circuit.
- Wires selected incorrectly for wiring.
- Weak and unreliable contact at the junction of two conductors or when connected to an outlet, switch, junction box. If the wiring is old, a twisted joint may occur. If the contact is improperly closed, it quickly heats up, collapses, and may shorten.
- Damage to the electrical appliance, which leads to shorting of the entire electrical circuit.
When two exposed conductors of different poles come into contact, the temperature rises sharply at the point of contact, and a short circuit may occur in this area.
Short circuit current calculation
Short circuit voltage is the voltage at which an electric current equal to the rated current flows on the closed winding of the transformer.
Short circuit voltage can be determined by the voltage drop across the transformer. This value characterizes the total resistance of the windings.
Short-circuit currents significantly exceed the rated value for which the entire electrical circuit is designed. They can burn out weak spots, destroy them and cause a fire.
To exclude an emergency, specialists at the design stage begin to deal with the defect and calculate the theoretical possibility of high currents. Based on the calculated data, the power elements and protective components of the circuits are selected. They struggle with large currents during equipment operation.
Calculation of the current of single-phase short-circuit and three-phase is carried out using Ohm's law, the impedance of the circuit, power characteristics of the power and structure of the used electrical installation. Accuracy may vary depending on the purpose of the instrument.
Possible consequences
Short circuit is a negative phenomenon that can lead to fire and damage to household appliances. But you can also highlight other problems caused by the defect:
- Smelting lived. In the event of an explosion, they could be harmful to human health.
- Ignition insulation. Actual for low-quality insulating layers or made of flammable materials.
- Damage to equipment.
In order to prevent all negative consequences, you need to find a short circuit in time and eliminate it.
Methods for finding a closure
It is almost impossible to determine in advance where there is a risk of a short circuit, especially if the wiring is new. Usually they search after knocking out machines.
How to find a short circuit in the wiring:
- Visual inspection of wires. It is necessary to check the integrity and type of insulation, the absence of kinks of cables and burnt shell. Particular attention should be paid to areas in which the extension and connection of wires was carried out. You also need to look for and check the connection points to the distribution panel, outlet, switch.
- Testing with the help of special instruments - megaohmmeters, multimeters, testers. Using a device showing circuit resistance, you can find a short circuit. Probe tester need to touch the phase and zero, then to ground. If the display shows zero, the wiring is OK. When any value appears, you can judge the contact of the contacts. Keep in mind that using a multimeter is not always possible to find a short circuit. It is usually used for sections of electrical circuits up to 3 meters.
- A short circuit can occur not only in the wiring, but also on the household appliance itself, included in the network. It is not difficult to calculate the problem then - in an emergency, the machine will be knocked out. It is necessary to disconnect all equipment from the sockets, turn on the circuit breaker and alternately connect each device to the mains. By means of exclusion, a broken part of the chain will be found.
- Search by sound. This is an unreliable folk method that is better not to use. The bottom line is this: when shorting contacts, a characteristic crack occurs. On this basis is a failed site. Problem spots are also found by the smell of burnt plastic.
The surest way to find problem areas is to check with a tester. It is not possible to reliably determine the location of a short circuit by sound or smell.
How to eliminate
When a place is found where the wiring is short, it is necessary to carry out its replacement and repair. Previously, the room must be de-energized and only then change the problem area. The junction of the two conductors must be reliably insulated. It is also important to choose the right way to create a contact. If a circuit breaker or socket burns out due to short-circuit current, it is recommended that you purchase and install a new product. It is cheaper and more reliable than repairing a broken device.
In old houses, electrical wiring was made of aluminum. This is an unreliable outdated way to lay networks, so it needs to be completely replaced. It is aluminum wiring that can short-circuit.
When a household appliance closes, a professional should fix it. It is dangerous for your health to repair the device yourself without a professional tool, skills and abilities.
Short circuit prevention
Performing preventive actions is safer, more reliable and cheaper than restoring wiring after a short circuit. Periodically check outlets. If they begin to sparkle, they need to be repaired or changed.
If the wiring was partially replaced, the reliability of the joints, the integrity of the insulating layer should be checked.
Every few months, light sources, lighting network and power wires should be checked.A short circuit may occur over time. You can identify it by changing the color of the devices or their melting. The apartment must always have circuit breakers. Separate protective equipment is put on powerful electrical appliances, which should work in an emergency.
When conducting the wiring independently, it is important to correctly calculate the cable section. If it is unable to withstand the power of all connected devices, an overload will occur, leading to a short circuit. Cables should not be laid closely with each other - this can lead to damage to the protective layer. Also, when connecting, you must correctly select the method of creating a contact and purchase the necessary equipment in advance. You can not connect the wires by twisting.
If you need to drill a wall, you should check the place with a homemade metal detector or study the wiring diagram. This way you can detect hidden cable wiring that the master could have accidentally damaged.
