Introduction

Electricity is one of the many forms of energy governed by exact laws of physics.

Electrical energy is produced in power plants to prescribed quality standards and is transported by means of transmission and distribution networks to the end user. A range of external factors affect electricity during this long journey, and they may influence its quality.

Such factors include for example:

• atmospheric factors (for example a lightning strike),
• effects caused by using certain electrical appliances (for example electronic speed and energy regulators, power adapters of electronic devices etc.),
• effects caused by necessary interventions in the network,
• functioning of protection and automating devices designed to decrease the occurrence of network breakdowns,
• frequent switching on and off of big appliances.

The above-mentioned factors can cause:

• variations in supply voltage (power surges, supply voltage drops and outages)

Note:

In compliance with the ČSN 33 0420 standard, electrical appliances installed in low tension systems must withstand peak values of pulse voltage of up to 6000 volts.

To avoid damage to electrical appliances by lightning strikes (power surges), we recommend that you equip both new and current interior power distributions with surge protection. We also recommend disconnecting electrical appliances from the power grid before the approach of thunderstorms.

• deviations from sine wave voltage (harmonic voltage)
• asymmetric supply voltage

Restriction and minimization of the impact of distribution network breakdowns on the customer

During distribution network breakdowns our primary task is to limit the impact of these unforeseeable conditions on the end user as much as possible. There are many automation systems (for example re-shutting systems) and protection devices that serve to locate the breakdown and disconnect the faulty spot from the distribution network as fast as possible.

During this time, the properties of electricity, which are governed by the laws of physics, the type of automation systems used and the character of the network, may change. Most often, short-term supply voltage drops and outages occur. After this period of time, only the affected part of the network remains cut off from supplies.

The supplier is entitled to interrupt or restrict electricity supplies according to a closed contract in circumstances including the following:

• upon the occurrence of direct hazard to life, health or property,
• upon the occurrence and the fixing of breakdowns
• upon performing necessary operational maintenance for a maximum of 30 minutes,
• upon performing scheduled tasks.

E.ON Energie, a.s., supplies electricity that conforms to EU quality standards.

The qualitative properties of electricity are defined in standards ČSN EN 50 160 and ČSN IEC 38.

Network voltages

Rated phase voltage in low voltage networks is 230 V.
Rated delta voltage in low voltage networks is 400 V.

Under normal conditions, the voltage in the network must be within ± 10 percent of the rated value, i.e. the voltage may vary between 207 to 253 V. Ninety-five percent of average values of supply voltage in 10-minute measurement intervals must fall within this range each week.

The rated frequency is 50 Hz. Under normal conditions, the network frequency has to fall within a ± 1 percent range for 99.5 percent of the year.

Our company doesn't guarantee the accuracy of clock time, which is derived from the frequency of the network (synchronous clock).

Deviations from the ideal voltage characteristics and symmetry occur mainly as a result of the properties of the connected electrical appliances. To limit these effects, our company performs network monitoring and subsequent technical adjustments.

The transfer of information and data among customers over E.ON Distribuce distribution networks is not permitted.

Three-phase appliances or appliances with higher demands on the quality of electricity can only be connected on condition that they are protected by appropriate technical equipment designed to limit the negative impact of the following effects:

• individual phase voltage loss in the case of three-phase appliances,
• voltage oscillations in the case of appliances sensitive to short-term voltage drops or outages,
• changes of frequency in the case of appliances sensitive to these changes.

Our company routinely supplies you with electricity of the prescribed quality, which, as already mentioned, conforms to European standards. This quality is generally high enough for you to be able to operate and use a vast majority of electrical appliances without any trouble. For appliances that are especially sensitive to deviations from the rated values of supply voltage or for appliances used in areas where increased reliability is required, improper functioning or damage can be avoided only on condition that appropriate technical measures are taken.

The following appliances are especially sensitive to power surges:
computers, chip controls, audio-visual devices, light regulators, video devices, satellite receivers, telephone switchboards, fax machines etc.

The following appliances are especially sensitive to low voltages:
refrigerators, freezers, washing machines etc.

If you want to use devices and appliances for which the supplied quality of electricity is insufficient (especially regarding power surges), we recommend that you find out from the supplier of the particular appliance about the sensitivity and resilience of the appliance and potential protective measures prior to purchase.

Conditions for safe electricity usage

1. When using safe, standard-compliant wiring and safe appliances, electricity is a reliable source of light and heat, and it enables the further functioning of various appliances in the home, while posing no risk to health or property.
2. Repairs and maintenance of wiring and appliances, including mobile and extension cords, should only be entrusted to a specialist company.
3. Protect the appliances and wiring from people who have a reduced ability to identify danger (children, mentally handicapped people etc) for example by blinding sockets or locking switches. Also protect domestic animals from potential electric shock (biting a supply cord etc.)
4. Only buy and plug in safe appliances.
5. Use appliances only for the purposes they were designed for and according to instruction manuals.
6. Appliances and wiring must be protected in the appropriate way. The method and implementation of protection must conform to the appropriate technical standards. Common wiring protection elements may not suit appliances with higher electrical quality demands.
7. You must not replace screw fuses with stronger ones, nor try to repair them. You would put your own life and the lives of others at risk.
8. We recommend unplugging appliances during thunderstorms.
9. CAUTION!
   Passing through the human body, electricity can cause injury or death. Observe the basic guidelines mentioned above.

Characteristics of safe products

1. The product must be complete. Covers and controls must not be missing, damaged or loose.
2. Mobile and extension cords must conform to the appropriate standards. Don't use homemade extension cords!
3. No parts of the product may be damaged by heat (warped, burned, charred etc).
4. Electrical parts of the product must not come into contact with water unless they were specified to do so in the instruction manual.
5. Make sure that your wiring does not get overloaded and that it is inspected at regular intervals.

Electrical appliance purchase recommendations

1. Make sure that:
   • the appliance's label bears the designation 230 V or 230/400 V and 50 Hz,
   • the appliance's label includes the designation of manufacturer (name or trademark),
   • the appliance is labeled CE or CCz (CE labeled appliances conform to EU standards, CCz labeled appliances have been tested by a Czech test laboratory and conform to Czech standards),
   • the manufacturer equipped the appliance with a connector plug. If not, the connection has to be implemented by a specialist company,
   • the appliance is equipped with a Czech language instruction manual.
2. Safe appliances should be resistant to damage from electricity outages.
3. If you have any doubts regarding the quality and safety of electrical appliances, ask to be presented with a declaration of conformity with the requirements of current technical standards (Act 22/1997 Coll., on technical requirements of products).
4. Keep all purchasing, connection and maintenance records for appliances and wiring.

What to do if you suspect flaws in electricity

1. If your appliance doesn't work as you expected it to, the malfunction may not be caused by an electrical defect. Check the connection and usage, consulting the appliance's instruction manual.
2. If your appliance still doesn't work, find out whether this is also the case with other appliances. If you suspect the appliance to be defective, contact a specialized repair shop. Don't intervene in the appliance or in the wiring by yourself.
3. If the appliance and wiring have no defects, contact us - see the Contacts section.