Mains electricity

When mains voltage is referred to the information provided by the energy suppliers in power systems electrical voltage which is used for the transmission of electric power. In addition to the voltage of the high and medium voltage networks is connected to mains often the magnitude of the AC voltage understood in the low-voltage networks.

Low voltage

Characteristics

The supplied by the power supply at the grid connection point mains voltage is in accordance with IEC 60038 ( in Germany: DIN EN 60038 VDE 0175-1 ) characterized by their:

• Rated voltage: for single-phase systems: effective value of the sinusoidal AC voltage between phase conductor and neutral conductor
• In three-phase systems: effective value of the sinusoidal AC voltage between two phase conductors

In Europe, other features of the voltage ( frequency, height, curvature and symmetry of the phase voltages ) in the standard EN 50160 are fixed.

Distribution

Europe

To the buyers in the low-voltage grid, the grid voltage is usually distributed with the following configurations in TN systems:

• The three external conductors (phases) (L1, L2, and L3),
• A neutral conductor (N) and
• A protective conductor (PE = protective earth or ground potential )

Or

• The three external conductors (phases) (L1, L2, and L3 ), and
• A PEN conductor. In this neutral and protective conductors are combined in a single conductor.

In Europe, the line voltage is 230 V ± 10%.

In three-phase systems, the rms value of the sinusoidal AC line voltage is 230 V between one phase and neutral and 400 volts between two phase conductors with a mains frequency of 50 Hz

North and South America

In Canada, the U.S., Mexico and some of the northern countries of South America, the nominal value of the AC voltage is 120 V. For larger appliances such as air conditioners is also twice the mains voltage of 240 V common. The mains frequency is 60 Hz low-voltage networks are implemented in these countries as single-phase three-wire system, a three -phase alternating current is smaller buyers often not available, if it exists, then the voltage is 208 or 415 V.

In Brazil, according to the region 110 V, 127 V or 220 V offered, each with 60 Hz southern countries Chile, Argentina, Bolivia, Paraguay and Uruguay have 220 ​​V at 50 Hz

Asia

In the Japanese power supply, the mains voltage is 100 V ( 50 Hz or 60 Hz region ) has the lowest value. Taiwan is the mains voltage 110 V, in China, Hong Kong and Thailand 220 V (50 Hz). India has as Europe a 230 V power (at 50 Hz).

History

By 1987, the network voltage was in many parts of Europe, including Germany, Austria and Switzerland, 220 V 240 V. Since that time, valid in Europe voltage of 230 V was with a tolerance of ± 10%, in the United Kingdom in the international standard IEC 60038:1983 set as the default voltage.

From 1987, first we have moved in several gradations to 230 V 6 % and -10 %. Since 2009 the mains voltage of 230 V may differ by ± 10%, so 207 volts to 253 volts allowed.

For 220 volt specified electrical consumers could in the consideration of the valid 1987-2009 tolerances with 230 V ( 6 %, -10% ) can be operated without the tolerance conditions to serious injury: The maximum voltage was 220 V, 242 V, at 230 volts 243.8 volts. Since 2009, this is no longer true, as the maximum voltage is 253 V now.

When was the minimum voltage and the tolerance band is not violated: While earlier were 198 volts allowed, there are now at least 207 volts.

Increasing the voltage by about 5% leads to an increase in number of devices of the service. For devices whose function is based on the ohmic resistance, such as a fan heater or kettle, consumption increases quadratically with respect to the voltage increase, ie by about 10%. In many cases, the payable amount of energy remains approximately the same, as for example a kettle because of the higher power, the given amount of water warms up faster and shuts correspondingly earlier.

Incandescent light bulbs, this increase is due to the usual PTC characteristic of the filament slightly lower. However, higher voltage means lower energy losses on the lines when the same power is transferred. Incandescent light bulbs it comes with a higher filament temperature but a shortening of the ( statistically probable) of operation.

Disturbance of the system voltage

The sinusoidal shape of the mains voltage is increasingly disturbed by non-linear loads. These include gas discharge lamps, rectifiers, dimmer ( thyristor and triac controller ), frequency converters, compact fluorescent lamps and switching power supplies without reactive power compensation ( Power Factor Correction PFC).

On 1 January 2001 an EMC standard went into effect, lays down rules on the permissible low- noise spectrum ( harmonics ) for electronic consumer from 75 watts.

Even asynchronous network cause impurities, the so-called Nutenpfeifen. It is formed by the subdivision of the cage rotor and caused thereby, fed back into the grid AC voltage with a higher speed- dependent frequency.

The line frequency is now maintained very precisely according to the requirements of the European interconnected system, so you can use it as a reference value, for example for control of electric clocks.

Protection against contact

The contact of the mains voltage conductors can be fatal. The mains voltage is above the protective low voltage or low voltages. For this reason, hot connections must be made both for the supply lines as well as the operated with mains voltage equipment protection measures against electric shock when touched.

These include protective insulation, protective earthing and protective separation that prevent exposed conductive parts carry hazardous voltages (eg housing) with a defect.

Sockets must be protected against contact with live parts. For the protection of children, there are also parental controls that will prevent insertion of objects into the openings of outlets.

Medium voltage

Larger consumers such as industrial plants and hospitals are usually connected directly to the medium-voltage grid at voltages of 10 kV or 20 kV via one or more in-house transformer stations.

High voltage

Even in high-voltage networks almost always standard voltages are used. Thus, the voltages 220 kV ( kilovolts ) and 380 kV are used in the high voltage network in Europe mainly. The high-voltage network is operated normally with 110 kV, however, is found especially in large cities with older cable systems, a 60 - kV network before.

In other regions are partly different voltage levels common: To exist in Russia high voltage networks with 1150 kV, 750 kV, 500 kV and 330 kV, while the stresses in the high voltage grids in the U.S. 765 kV, Canada 735 kV, 500 kV and 345 kV amount. For high voltage networks in the U.S., the value 132 kV common.

In the medium-voltage network, in addition to 20 kV, especially in urban areas because of there older cable systems and 10 kV usual. In the high-voltage DC transmission there are no normalized voltages.

In railway power supply networks, the standard voltage in Germany and Austria is 110 kV, 66 kV in Switzerland and 132 kV.

Traction power

In railway operation itself ( overhead lines ), numerous tensions have prevailed. In full tracks the following five systems dominate (see list of Traction Power Systems):

• Single-phase AC 50 Hz, 25 kV
• Single-phase AC 60 Hz, 25 kV
• Single-phase AC 16.7 Hz, 15 kV ( only Germany, Austria ( new high-speed lines 50 Hz, 25 kV), Switzerland, Norway, Sweden, and 1995 16 ⅔ Hz)
• DC voltage, 3 kV
• DC voltage, 1.5 kV

In underground and trams, the voltage is not standardized. In Germany and Austria dc voltage of 500 V up to 750 V is used here mostly.