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In electrical engineering, ground and neutral (earth and neutral) are circuit conductors used in alternating current (AC) electrical systems. The neutral conductor receives and returns alternating current to the supply during normal operation of the circuit; to limit the effects of leakage current from higher-voltage systems, the neutral ...
United States electrical codes require that the neutral be connected to earth at the "service panel" only and at no other point within the building wiring system. Formally, the neutral is called the "grounded conductor"; as of the 2008 NEC, the terms "neutral conductor" and "neutral point" have been defined in the Code to conform to what had ...
In the United States National Electrical Code and Canadian Electrical Code, the feed from the distribution transformer uses a combined neutral and grounding conductor, but within the structure separate neutral and protective earth conductors are used (TN-C-S). The neutral must be connected to earth only on the supply side of the customer's ...
A somewhat similar system called "concentric wiring" was introduced in the United States around 1905. In this system, an insulated electrical wire was wrapped with copper tape which was then soldered, forming the grounded (return) conductor of the wiring system. The bare metal sheath, at earth potential, was considered safe to touch.
A grounding electrode conductor (GEC) is used to connect the system grounded ("neutral") conductor, or the equipment to a grounding electrode, or a point on the grounding electrode system. This is called "system grounding" and most electrical systems are required to be grounded.
In North American electrical codes, an important bonding jumper is found in main electrical panels, where the system neutral conductor is connected to earth ground. This must be done at only one point in each separately derived system to prevent flow of objectionable current in the earth.
Neutral to earth voltage (NEV) specifically refers to a difference in potential between a locally grounded object and the grounded return conductor, or neutral, of an electrical system. The neutral is theoretically at 0 V potential, as any grounded object, but current flows on the neutral back to the source, somewhat elevating the neutral voltage.
The system is common in North America for residential and light commercial applications. Two 120 V AC lines are supplied to the premises that are out of phase by 180 degrees with each other (when both measured with respect to the neutral), along with a common neutral. The neutral conductor is connected to ground at the transformer center tap.