Using a multimeter
You can see in the following video that the multimeter probe is inserted into the socket, the middle slot is the ground wire, and the two slots below are the live wire. If it is South America or some parts of the Philippines, their voltage is L1 + G = 110V, L2 + G = 110V, L1 + L 2= 220V
The King of the Democratic Republic of the Congo has provided a solar energy storage power station system for the village of Bunkeya to meet the electricity needs of 2500 small households in the village. As the village currently lacks access to the grid, the King requested the design of a 1MW solar panel system paired with a 1.8MWh lithium battery storage system to power the entire village.