Which country uses 400v?

Three-phase electric power (industrial applications only) CountryThree-phase voltage (volts)Frequency (hertz)Australia400 V (officially, but in practice often 415 V)50 HzAustria400 V50 HzAzerbaijan380 V50 HzAzores400 V50 HzComplete list: Three-phase electric power (voltages/frequencies) www.worldstandards.eu › electricity › three-phase-electric-power

Voltage is an electrical quantity designating the potential difference between two points, frequency is the quantity designating the number of direction changes of a wavy quantity (like the number of zero crossings of an AC current, or the number bukles of an ocean wave, etc.).

The Nigerian Grid Code Frequency Standard is 49.75Hz and 50.25Hz while the WAPP Frequency standard is 49.80Hz and 50.20Hz . Currently West African Power Pool operates three islands due to poor frequency control.