The line voltage is the supply voltage for devices and systems that is transmitted via the low-voltage network. It is a sinusoidal alternating voltage that is specified with its effective value. In Germany and many other countries, the effective value of the mains voltage is 230 V. It is an alternating voltage with a frequency of 50 Hz. In the USA or Canada it is 120 V and 60 Hz.
The low-voltage grid is a three- phase power grid, each phase of which is offset from the other by 120°. The power grid can be operated as a single-phase power grid or, for higher loads, as a three-phase power grid with three-phase current. In single-phase operation, the current is conducted to the consumer on two conductors: one conductor is the phase-conducting conductor, the current conductor (L) or outer conductor, and the second is the neutral conductor (N) or neutral conductor. The neutral conductor is connected to the neutral point of the supply voltage. The third conductor is the protective conductor( PE), which is connected to ground potential and provides protection against contact.
Conductors in the low-voltage network: neutral conductor (blue), protective conductor (green-yellow) and current conductor (black).
The three conductors of a single-phase low-voltage network are color-coded. The current-carrying outer conductor is black, the neutral conductor is blue and the protective conductor is green/ yellow. The mains voltage is standardized by the International Electrotechnical Commission( IEC) under IEC 60038 and was increased from 220 V (effective) to 230 V in Germany in the 1980s. The tolerance in the voltage deviation is +/-10 %.
The mains voltage is a sinusoidal alternating voltage with a frequency of 50 Hz. This means that it changes polarity 100 times per second between a positive and a negative peak voltage. As for the peak voltage of the AC voltage, the peak value of a sinusoidal AC voltage is calculated as 1.414 times the effective value. This means that the AC voltage has a positive and negative peak voltage of 325 Vs each. The peak-to-peak voltage is therefore 650 Vpp.