to the earth. In a TT system, no lengthy common protective ground conductor is used, instead each article of electrical equipment (or building distribution system) has its own connection to earth ground. Indian CEAR, Rule 41, makes the following provisions: The neutral conductor of a 3-phase, 4-wire system and the middle conductor of a 2- phase, 3-wire system must have at least 2 separate and distinct earth connections with a minimum of 2 different earth electrodes to have a satisfactory earth resistance The earth electrodes must be interconnected to reduce earth resistance The neutral conductor shall also be earthed at one or more points along the distribution system or service line in addition to any connection at the user end Combining neutral with ground Stray voltages created in grounding (earthing) conductors by currents flowing in the supply utility neutral conductors can be troublesome. For example, special measures may be required in barns used for milking dairy cattle. Very small voltages, not usually perceptible to humans, may cause low milk yield, or even mastitis (inflammation of the udder). So-called "tingle voltage filters" may be required in the electrical distribution system for a milking parlour. Connecting the neutral to the equipment case provides some protection against faults, but may produce a dangerous voltage on the case if the neutral connection is broken. Combined neutral and ground conductors are commonly used in electricity supply companies' wiring and occasionally for fixed wiring in buildings and for some specialist applications where there is little alternative, such as railways and trams. Since normal circuit currents in the neutral conductor can lead to objectionable or dangerous differences between local earth potential and the neutral, and to protect against neutral breakages, special precautions such as frequent rodding down to earth (multiple ground rod connections), use of cables where the combined neutral and earth completely surrounds the phase conductor(s), and thicker than normal equipotential bonding must be considered to ensure the system is safe. Fixed appliances on three-wire circuits In the United States, the cases of some kitchen stoves (ranges, ovens), cook tops, clothes dryers and other specifically listed appliances were grounded through their neutral wires as a measure to conserve copper from copper cables during World War II. This practice was removed from the NEC in the 1996 edition, but existing installations (called "old work") may still allow the cases of such listed appliances to be connected to