Power problems are a common cause of electrical breakdowns. One of the most common negative phenomena is a short circuit. It is dangerous not only for technology, but also for the house itself, as it can lead to a fire. You can deal with a short circuit using fuses and circuit breakers in an active circuit. But in the case of a de-energized wire or device, finding a short circuit becomes more difficult. There are different ways to find and fix a network defect.
Short circuit reasons
The main factor causing a short circuit is a sharp increase in current. It is accompanied by a decrease in the resistance of the wiring and leads to an increase in temperature above normal values. This leads to the fact that flammable materials can ignite.
Why short circuit occurs:
- Deterioration of the power grid Over time, the insulation wears out, part of the wire is exposed, and a short circuit can occur in this area.
- Moisture. Liquid spillage on the twist-protecting tape can occur during flooding. This will peel off the sticky side of the tape and expose the joint.
- Mechanical impact on insulation. During repair work, it is possible to accidentally drive a nail into the cable route and damage the protective layer. Rodents can also gnaw through the wires.
- Overloading the power grid for a long time. Melts the insulation.
- Incorrect selection of circuit breaker rating. The protection device may not react and miss voltage surges, which increases the risk of a short circuit.
- Incorrectly selected electrical wires 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, there may be a twist connection. If you close the contact incorrectly, it quickly heats up, collapses and can short.
- Breakdown of an electrical appliance, which leads to a short circuit of the entire electrical circuit.
When two bare cores of different poles touch, the temperature rises sharply at the point of contact, and a short circuit may occur in this area.
Short-circuit current calculation
The short-circuit voltage is the voltage at which an electric current equal to the rated current flows on the closed winding of the transformer.
You can determine the short-circuit voltage by the voltage drop across the transformer. This value characterizes the impedance of the windings.
Short-circuit currents are significantly higher than the rated value for which the entire electrical circuit is designed. They can burn out weak points, destroy them and lead to fire.
To exclude an emergency situation, specialists at the design stage begin to deal with the defect and calculate the theoretical possibility of the occurrence of large currents. Based on the calculated data, the power elements and protective components of the circuits are selected. They also deal with large currents during the operation of equipment.
The calculation of the current of a single-phase short-circuit and three-phase is carried out using Ohm's law, the impedance of the circuit, the power characteristic of the power and the structure of the electrical installation used.Accuracy may vary depending on the intended use of the instruments.
Possible consequences
A short circuit is a negative phenomenon that can lead to fire and damage to household appliances. But there are also other problems caused by the defect:
- Melting veins. In the event of an explosion, they can harm human health.
- Ignition of insulation. Relevant for low-quality insulation layers or made of flammable materials.
- Breakdown of equipment.
In order to prevent all negative consequences, you need to find a short circuit in time and eliminate it.
Closure Search Methods
It is almost impossible to determine in advance the place where there is a risk of a short circuit, especially if the wiring is new. Usually, the search is done after knocking out the machines.
How to find a short circuit in a wiring:
- Visual inspection of wires. It is necessary to check the integrity and type of insulation, the absence of kinks in cables and a burnt sheath. Particular attention should be paid to the 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 switchboard, outlet, switch.
- Checking with special devices - megohmmeters, multimeters, testers. A short circuit can be found with a device showing the resistance of the circuit. With the tester probes, you need to touch the phase and zero, then to the ground. If the display reads zero, the wiring is OK. When any value appears, one can judge the contact of the contacts. It should be borne in mind that it is not always possible to find a short circuit with a multimeter. 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, connected to the network. It is then easy to calculate the malfunction - in case of an emergency, the machine gun will knock out. It is necessary to disconnect all equipment from the sockets, turn on the circuit breaker and alternately connect each device to the mains. The broken section of the chain will be found by the method of elimination.
- Search by sound. This is an unreliable folk method that is best not used. The bottom line is the following - when the contacts are short-circuited, a characteristic crackle occurs. On this basis, there is a failed site. They also find problem areas by the smell of burnt plastic.
The surest way to find problem areas is to check with a tester. It is impossible to reliably determine the location of a short circuit by sound or smell.
How to fix
When a place is found where the wiring is short, you need to replace and repair it. First, the room must be de-energized and only then the problem area must be changed. The junction of the two conductors must be securely insulated. It is also important to choose the right way to create a contact. If a switch or socket is burnt due to the short-circuit current, it is recommended to purchase and install a new product. It is cheaper and more reliable than fixing a broken device.
In older houses, electrical wiring was made of aluminum. This is an unreliable, outdated way of laying networks, so it needs to be completely replaced. It is the aluminum wiring that can short-circuit.
When a household appliance is closed, a professional should be involved in the repair. It is dangerous to your health to repair the device yourself without professional tools, skills and abilities.
Short-term prevention
If a partial replacement of the wiring was made, the reliability of the connection points, the integrity of the insulating layer should be checked.
The light sources, lighting network and power wires should be checked every few months. Short circuits can develop over time. It can be identified by changing the color of the devices or melting them. The apartment must have automatic switches. Separate protective equipment is installed on powerful electrical appliances, which must be triggered in an emergency.
When carrying out the installation of electrical wiring yourself, it is important to correctly calculate the cable cross-section. If it is not able to withstand the power of all connected devices, an overload will occur, leading to a short circuit. The cables should not be laid close to each other - this can damage the protective layer. Also, when connecting, you must choose the right way to create a contact and purchase the necessary equipment in advance. Do not connect 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. Thus, you can find a hidden wiring cable that the master could accidentally damage.
