WIRING SCHEMES AND GROUNDING Electrical Distribution SystemsTerminologyTo understand wiring schemes used in power distribution systems, you must be familiar with thefollowing terms.Ampacity - the current in amperes that a conductor can carry continuously underthe conditions of use without exceeding its temperature rating.Bond - the permanent joining of metallic parts or circuits assuring electricalcontinuity and capacity to safely conduct any current likely to be imposed.Conductor - any wire, cable, or substance capable of carrying an electrical current.Ground - a conducting connection, whether intentional or accidental, between acircuit or piece of equipment and the earth, or some body serving as earth; a placeof zero electrical potential.Ground voltage - the voltage between any given conductor and any point atground potential.Leg - a current-carrying conductor intended to deliver power to or from a loadnormally at an electrical potential other than ground.Neutral - a current-carrying conductor normally tied to ground so that theelectrical potential is zero.Phase voltage - the greatest root mean square (effective) difference of potentialbetween any two legs of the circuit.Single-PhasePowerThe source of single-phase (1f) power in all facilities is by generation from a single-phasegenerator or by utilization of one phase of a three-phase (3f) power source. Basically, eachphase of the 3f distribution system is a single-phase generator electrically spaced 120 degreesfrom the other two; therefore, a 3f power source is convenient and practical to use as a sourceof single-phase power.Single-phase loads can be connected to three-phase systems utilizing two methods. The diagramshown in Figure 15 illustrates these connections.ES-15 Page 22 Rev. 0
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