AC voltages have been classified in various manners. In earlier times, there were just two categories LV and HV. As the level of voltages increases, there was a need for more levels. However, there was ambiguity as to where each band ended and the other began. For instance, 11kV can be MV in some systems and HV in another.
The International Electrotechnical Commission has classified the voltages into the following levels(IEC 60038). This classification system is fast gaining acceptance.
- Low Voltage - upto 1000V
- Medium Voltage - 1000V to 35kV
- High Voltage - 35kV to 230 kV
- Extra High Voltage - above 230 kV
In some situations, the term Ultra High Voltage is used to denote voltages above 800 kV.
In addition, the IEC defines a voltage band known as the Extra Low Voltage with a AC voltage less than 70 V.
Extra Low Voltage
Extra low voltage refers to reduced voltages which are used in houses, parks, gardens, swimming pools to eliminate the risk of electric shock.
AC voltages below 50 volts and DC voltages below 120 volts are considered to be Extra low Voltage.
In many countries, Extra Low Voltage supplies are used to power traffic signals. This has been facilitated with the advent of LED lighting technology.
Extra Low voltage systems can also be easily integrated with solar panels as the generating voltage is lower.
