Overvoltage is an abrupt increase in voltage on a power line. Let's give an example: a single-phase network has a voltage of 220 V - this is the effective voltage. If you translate it into amplitude, you get 310 V. When a surge voltage occurs, the peak value of the indicator reaches several thousand volts. Such a jump does not last long - a few milliseconds, but in such a short period of time, quite unfavorable phenomena can occur. In this article, we will consider the causes of overvoltage in the network, as well as the types of this phenomenon and measures to protect against it.
Content:
- Why is this phenomenon dangerous?
- Varieties of overvoltage
- Atmospheric
- Commutation
- Transitional
- Electrostatic
- Protective measures
Why is this phenomenon dangerous?
The overvoltage in the mains is as follows:
An electrical network with insulation of electrical cables and wires, as well as any electrical appliances, can only withstand a certain voltage level. Below is a table that indicates the dielectric strength of the insulation of electrical equipment.
As you can see from the table, almost all devices and devices are not able to withstand high rates, most devices can only withstand up to 1000 V.
What will overvoltage lead to? This will lead to damage to electrical wiring and electrical appliances. It can also cause a fire, as the insulation is broken and occurs short circuit. After all, the power grid (cable lines of electrical wiring) is constantly energized. If an electrical appliance can be protected from damage by unplugging it from the outlet, then electrical wiring is difficult to protect. The photo shows a surge voltage in the form of a short circuit, which occurred in the network as a result of insulation breakdown in the outlet.
Low-quality manufacturers are not always considered the cause of failure of electrical appliances and equipment. Overvoltage in the network plays an important role in this matter.
Varieties of overvoltage
First of all, it should be noted that overvoltage is divided into four types:
- atmospheric or thunderstorm;
- switching;
- transitional;
- electrostatic.
Let us briefly consider the causes of each type of hazardous situation.
Atmospheric
This species belongs to natural phenomena and is considered to be the most dangerous, as it is caused by lightning discharges. With strong atmospheric precipitation, similar discharges occur, when a strong impulse overvoltage reaches tens of thousands of volts in one millisecond.
Lightning can strike directly into the power grid (overhead line), or into a lightning rod. Overvoltage can also occur as a result of an electric discharge hit at a distance of up to 1500 meters.
Impact impulses come in various shapes and lengths. For example, the figure shows two types of waves - 10/350 and 8/20. And judging by the schedule, the 10/350 wave is the most dangerous for the facility, since it has a much stronger effect on the local network.
It should be noted that in the presence of a lightning receiver that protects the object from a lightning discharge, half the primary impulse is diverted to the ground, and the remaining half is evenly distributed between the conductors electricity in the house.
Commutation
This phenomenon occurs when the local network abruptly changes its standard mode of operation. This can be the result of sudden switching on or off of powerful equipment. This is the so-called transition process. With a similar phenomenon, pulses and waves reach high frequencies (tens - hundreds of kHz), and the value acquires several thousand volts and, as a rule, depend on what characteristics and parameters possesses a network.
The causes of overvoltage can be different. For example, turning off or turning on circuit breakers or other devices and mechanisms relay protection, start-up of powerful electric motors, power transformers, batteries of statistical capacitors.
For example, if a low power (1 kVA) transformer is disconnected from the power supply, a switching overvoltage of up to 2000 V may occur as a result. This means that all the energy that is stored in the transformer windings enters the network and can cause breakdown and malfunction of electrical equipment.
Transitional
A similar phenomenon occurs as a result of power frequency voltages. For example, due to damage to the neutral conductor (with insulated neutral) or phase / housing of the electrical installation and other internal damage.
Electrostatic
This phenomenon occurs, as a rule, in dry environments, when electrostatic charges accumulate and an electrostatic field is formed. Electrostatic overvoltage is considered unpredictable and unusual, so the effects can vary as well.
For example, if you wear dielectric shoes, then when walking on a carpet, a person is charged up to several thousand volts. And if after that you touch any structure that has conductive properties (for example, batteries or computer case), an electrical discharge will occur, which lasts for several nanoseconds. This kind is considered to be very dangerous for electronic parts in electrical equipment and devices.
About, how to protect yourself from static electricity, we told in the corresponding article on the site!
Protective measures
The electrical network plays an important role in human life, without it today's existence is impossible. Therefore, it is necessary to protect your electrical equipment from such a phenomenon as overvoltage. It is impossible to completely remove the impulse manifestation, but you can reduce its value to such an indicator that will not harm the equipment.
To protect the electrical network and appliances at home, you must:
- install lightning protection - lightning rod;
- install SPD - a special protection mechanism that lowers the dangerous impulse voltage of 6-10 kV to a safe one;
- connect the potential equalization system.
Learn more about overvoltage protection devices we talked about in the corresponding article, which we strongly recommend that you familiarize yourself with!
Important! Do not know who compensates for the damage when the electrical appliances did burn out? An energy-saving company is fully responsible for the network. Therefore, first of all, you should go there and write a statement, which indicates the damage caused.
Finally, we recommend watching a useful video on the topic:
Here we examined what an overvoltage in the network is, what are the reasons for its occurrence and how to protect yourself from this phenomenon at home. We hope you found the information provided useful!
You probably don't know:
- How to make a lightning rod with your own hands
- How to deal with power surges
- Why does it shock in the bathroom?
