(1) Phase line (L). Conductors that carry electrical energy are normally not grounded.
(2) Neutral line (N). Connected to the neutral point of the system and can act as a conductor for the transfer of electrical energy.
(3) Protection Neutral (PEN). A conductor that has both a protective wire and a neutral wire.
(4) Power grounding point. Ground the point where the power supply can be grounded (usually the neutral point).