Where a neutral conductor is used also to methods of neutral grounding pdf equipment enclosures to earth, care must be taken that the neutral conductor never rises to a high voltage with respect to local ground. The terms “ground” and “earth” are used synonymously here.
Ground” is more common in North American English, and “earth” is more common in British English. Under normal conditions, a grounding conductor does not carry current. Adding new grounds requires a qualified electrician with information particular to a power company distribution region. That is for simple single panel installations, for multiple panels the situation is more complex.
In the electrical trade, the conductor of a 2-wire circuit connected to the supply neutral point and earth ground is referred to as the “neutral”. Canadian electrical code only define neutral as the grounded, not the polyphase common connection. Neutral conductors are usually insulated for the same voltage as the line conductors, with interesting exceptions. Other arrangements of polyphase transformers may result in no neutral point, and no neutral conductors. The letter symbols are common in countries using IEC standards, but North American practices rarely refer to the IEC symbols. The differences are that the conductors may be separate over their entire run from equipment to earth ground, or may be combined over all or part of their length.
Different systems are used to minimize the voltage difference between neutral and local earth ground. Current flowing in a grounding conductor will produce a voltage drop along the conductor, and grounding systems seek to ensure this voltage does not reach unsafe levels. Normal circuit currents flow only in the neutral, and the protective earth conductor bonds all equipment cases to earth to intercept any leakage current due to insulation failure. The neutral conductor is connected to earth at the building point of supply, but no common path to ground exists for circuit current and the protective conductor. In the TN-C system, a common conductor provides both the neutral and protective grounding. The neutral conductor is connected to earth ground at the point of supply, and equipment cases are connected to the neutral. The danger exists that a broken neutral connection will allow all the equipment cases to rise to a dangerous voltage if any leakage or insulation fault exists in any equipment.
This can be mitigated with special cables but the cost is then higher. In the TN-C-S system, each piece of electrical equipment has both a protective ground connection to its case, and a neutral connection. These are all brought back to some common point in the building system, and a common connection is then made from that point back to the source of supply and to the earth. Neutral conductor of a 3-phase, 4-wire system and the middle conductor of a 2- phase, 3-wire system to have minimum two separate and distinct earth connections with a minimum of two different earth electrodes to have the earth resistance to a satisfactory value. The earth electrodes to be inter-connected to reduce earth resistance. Neutral conductor shall also be earthed at one or more points along the distribution system or service line in addition to any connection at user end. For example, special measures may be required in barns used for milking dairy cattle.