Damage prevention

Disturbances can be caused by weather events or when working on the power grid. By knowing what impact interruptions can have on your equipment, you can take preventive measures.

Common causes of disruption

  • over voltage pulses due to thunder and power grid connection
  • voltage drops due to switching operations, short circuits and starting of electrical equipment
  • interruptions and scheduled maintenance
  • voltage problems
  • Read more

    Observe the CE marking on electrical equipment

    For safety reasons, observe the CE marking on electrical equipment, which is the mandatory safety marking for appliances sold in the European Union. If an electrical appliance does not have the CE mark, the use of this appliance may be dangerous in our electrical system.

    Impact on electronic devices

    Voltage fluctuations and power cuts affect devices in different ways. Sensitive electronic devices as well as other property may be damaged.

    Read more about the impact of disturbances

    How to protect your electrical appliances

    During a lightning storm, you can best protect your electrical equipment by unplugging it. You can also choose between different protection devices for everyday protection. Installation of sophisticated equipment should be ordered by a professional electrician.

    Lightning protection system

    Helps in case of over voltage caused by lightning or switching operation in the power grid.

    Surge arresters

    Protects electrical equipment against surges and impulse currents.


    Provides protection for sensitive devices (such as computers) in the event of interruptions of up to 10 minutes.

    Voltage stabilizer

    Makes sub-standard voltage from the socket stable.

    Engine protection

    Engine circuit breaker to be used for protection of 3-phase electric engines (pumps, saws).

    Voltage control relay

    Protects your point of consumption from both over voltage and under voltage.

    Residual-current device

    Residual-current device shuts off power in the event of a hazard, helping to prevent more serious electrical accidents.


    In the event of a prolonged power failure, the generator will assist.

    Read more

    The impact of disturbances

    Over voltage can present a biggest risk to supplies for electronic devices and sometimes also the devices connected to it (TVs, digital boxes, computers, etc.) Elektrilevi's electrical system, though equipped with surge suppressors, does not always protect against lightning. Therefore, we recommend that you add additional protection to sensitive electronic equipment in your domestic electrical system.

    Possible causes of over voltage:

  • lightning strike
  • switching operations in the electricity grid
  • Voltage drops and voltage fluctuations can damage particularly sensitive electrical and electronic equipment, as well as their power supplies. In addition, the constant flashing of lights reduces the life of electric lamps and interferes with vision.

    Possible causes of voltage drops and fluctuations:

  • switching operations in the electricity grid
  • power line failures, such as fallen trees, icing, etc.
  • starting high power electric motors
  • proximity to major manufacturing plants and workshops
  • Planned interruptions are required for the repair and maintenance of an outdated power grid as well as for the construction of a new grid. When we are planning such interruption in your area, you will be notified well before. Interruptions or sudden power outages can be short and long lasting. Short-term interruptions (up to 3 minutes) are more common in cities where it is possible to quickly restore power through another line in the event of a malfunction. Such short-term power cuts have the greatest impact on electronic equipment.

    Prolonged power cuts (more than 3 minutes) are more common in rural areas where it takes longer to restore power. This is due to overhead lines used in rural areas which performance is affected by extreme weather conditions such as heavy snow, trees breaking in strong winds, icing on cables, low or high air temperatures and other natural influences. Forest and excavation work near the power lines may also cause malfunctions.

    In the case of a three-phase power supply, there are sometimes situations where there is no complete power failure but no voltage in one or two phases. In this situation, most home electrical appliances may work quite normally, but appliances powered by a 3-phase electric motor such as a power saw or pumps cannot be started. At worst, the loss of phase(s) can lead to the destruction of these devices.

    Characteristics of distribution networks

    Under normal operating conditions, except in the case of outages, slow changes in the supply voltage may not exceed ±10% of nominal voltage Un.

    In distribution networks not connected to the transmission networks or for special long distance users of the power network, slow changes in the supply voltage may not exceed +10% / –15% of nominal voltage Un. Users of the power network have to be informed of these circumstances.

    NOTE 1

    The actual power consumption of individual users of the power network is not fully predictable in amount or time. Due to this, power networks are generally planned based on probability. If after a complaint by a operator of the power network, measurements according to section show that the supply voltage value deviates from the limits given in section, causing negative results for the user of the power network, the operator of the power network must in cooperation with the user(s) of the power network take corrective measures according to the risk assessment. Temporarily, during solving the problem, slow changes in the supply voltage must stay between +10% / –15% of nominal voltage Un, unless otherwise agreed with the users of the power network.

    NOTE 2

    In accordance with the relevant product and installation standards and the implementation of standard IEC 60038, the current using equipment of the user of the power network is usually planned to tolerate deviations of supply voltage ±10% of the power network's nominal voltage, which is sufficient for most supply conditions. In general there is no need to plan current using equipment to tolerate larger voltage deviations.

    NOTE 3

    Considering various national characteristics of power systems, e.g. power limit in a connection point and/or power factor limits, the designation "special long distance user of the power network" can differ between countries. Source: EVS-EN 50160:2010 "Voltage characteristics of electricity supplied by public distribution networks" Full text of the standard can be read at the website of the Centre for Standardisation.

    How to protect your electrical appliances

    The lightning protection system consists of an external and an internal lightning protection system and must be used simultaneously. The external system protects the building against a direct lightning strike and consists of:

  • lightning rod (mostly a lightning rod)
  • rainwater gutters
  • earthing
  • If the building has an external lightning protection system, it is important to install an internal system, which usually contains surge arresters.

    For the installation of a lightning protection system, design and installation must be carried out by a professional electrician or electrical contractor.

    Surge arresters protect electrical networks and electrical equipment against surges and impulse currents caused by lightning and switching operations.

    Surge arresters are divided into types 1, 2 and 3. Type 1 and 2 and 1 + 2 surge arresters are used in the electrical supply of buildings (Type 1 or Type 1 + 2) and in the distribution boards of indoor wiring (Type 2).

    Type 1surge arresters are lightning-current proof - they are capable of passing powerful current impulses but do not restrict lightning impulses sufficiently (for example, for electronic devices).

    Type 2surge arresters limit the type 1 lightning impulses and furthermore the impulses generated by short-range and long-range lightning strikes or switches in the electrical system.

    Types 1 and 2surge arresters are usually installed in an electrical enclosure and should only be installed by a qualified electrician. We recommend that you consult an electrician or electric works company for the best solution.

    Type 3surge arresters are installed directly in front of the devices, i.e sockets. They help to eliminate the risk of over voltage pulses on electronic devices.

    Surge arresters that plug into a socket only work if they are connected to a grounded, three-wire, or grounded, electrical system. In electrical systems that do not have a protective earthing (mostly electrical systems built before 1995), this type of fuse will not work. Consult your dealer for specific recommendations and equipment for your home.

    The UPS is a backup power supply and voltage stabilizer that provides a solution to short-term interruptions of up to 10 minutes.

    The UPS can provide up to 400W of electrical power for up to 5 minutes, or up to 33 minutes for lower power. The UPS contains a battery to provide power to equipment connected to the UPS during a power outage. In addition, the UPS protects electrical equipment against surges caused by lightning and line breakage.

    It is not recommended to connect devices that run on an electric motor, such as a refrigerator, pump, heat pump, etc., as the starting current of an electric motor is usually several times bigger than the operating current indicated on the passport of these devices. Ask the electronics and construction stores for more information about UPS.

    The voltage stabilizer converts the socket out-of-standard (160-250V) voltage to a stable 230V voltage. Depending on the manufacturer, the power of domestic voltage stabilizers is between 500 and 2000 W.

    Voltage stabilizers should not be used to stabilize refrigerators, washing machines, heat pumps, power tools, and other devices powered by an electric motor.

    Before connecting the unit to a voltage stabilizer, make sure that your electrical equipment has a voltage stabilizer already built-in by the manufacturer. For many sensitive devices, double voltage stabilization is prohibited. Find out more about voltage stabilizers at electronics and construction stores.

    Use a special engine circuit breaker to protect 3-phase electric motors (such as machine tools, certain types of heat pumps), unless the device itself is protected.

    Voltage control relay (monitoring relay) protects your consumption point from voltage fluctuations including both over voltage and under voltage.

    The use of a voltage control relay is recommended if you use important or expensive electrical equipment (such as a heat pump) that is sensitive to voltage fluctuations, and especially if there is a recurring external power failure at your point of consumption. Non-standard voltages may also occur, for example, due to a line break. In this case the voltage control relay is a great help.

    The voltage control relay checks the voltage for compliance with the norm, the minimum and maximum of which are determined by the device to be protected. When the voltage exceeds the permitted range, the voltage control relay switches off the device (s). When the voltage returns to normal, the relay will turn the unit (s) back on.

    Have a voltage control relay installed by an electrical contractor or a qualified electrician.

    The RCD is as important in a household as a smoke detector. The RCD shuts off the power in the event of a hazard, helping to prevent a serious electric shock, save lives and reduce the risk of fire.

    The RCD is helpful if a human or animal comes into contact with malfunctioning electrical equipment housing which is under voltage.

    According to Estonian standards, in new electrical installations, RCD (actuation current of 30 mA) is mandatory for sockets with a nominal current of up to 32 A, as well as for lighting circuits. Be sure to use extra protection in all wet rooms, such as the shower room, bathroom, sauna and kitchen.

    The RCD-s have different starting currents. We recommend that you consult with an electrician to make the right choice. As with many other protective devices, the design and installation of an RCD to electrical system must be carried out by a qualified electrician or electrical contractor.

    A generator is a stand-alone power generating device that can be powered by either the entire electrical system, a part of it, or a single device that is most critical for power failure. When choosing a generator, make sure that its power is at least 20-25% higher than the rated power of the electrical system or electrical appliance as stated on the appliance or in the passport of the appliance.

    To connect the generator to the building's electrical system, a separate connection point with fuses and a switch must be built on the generator.

    The generator is an electrical appliance for which all safety requirements must be met. Before starting the power generator, carefully read the operating and safety instructions.

    A generator improperly connected to the electrical system is dangerous and can cause a fire, damage all electrical equipment due to overload, and be life-threatening to electricians who deal with malfunctions or carry out electrical work at the same time.

    Always have the generator installed by an electricity company or a qualified electrician.