The TN-C earthing system is a power supply system that combines the neutral wire (N wire) and the protective ground wire (PE wire) into one wire. Abstract - The most common medium voltage electric dis-tribution system in the United States is multigrounded wye using a common neutral for both primary and secondary systems. It offers high levels of safety and quick fault response. Grounding electrode conductors must be connected at accessible points from the load end of service conductors, with specific rules for outdoor transformers and. • Good system grounding provides the path for normal load and fault currents while maintaining load and controls temporary overvoltage. Good equipment grounding ensures personnel safety. Which circuit conductor must be grounded.