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Fuses are designed to melt and disconnect the circuit within which they are placed should the current in the circuit increase above a specified thermal rating. Fuses designed to be used in circuits operating above 600 V are classified as fuse cutouts. Oil-filled cutouts are mainly used in underground installations and contain the fusible elements […]

The Institute of Electrical and Electronics Engineers (IEEE) defines grounding as a conducting connection, whether intentional or accidental, by which an electric circuit or equipment is connected to the earth or to some conducting body of relatively large extent that serves in place of the earth. It is used for establishing and maintaining the potential

The process of connecting the grounding system to earth is called earthing and consists of immersing a metal electrode or system of electrodes into the earth. The conductor that connects the grounding system to earth is called the grounding electrode conductor. The function of the grounding electrode conductor is to keep the entire grounding system

Earth electrodes may be made electrodes, natural electrodes, or special-purpose electrodes. Made electrodes include driven rods, buried conductors, ground mats, buried plates, and ground rings. The electrode selected is a function of the type of soil and the available depth. Driven electrodes are used where bedrock is 10 ft or more below the surface. Mats

A bare rock mountaintop location provides special challenges to the facility design engineer. There is no soil, thus there are no ground rods. Radials are the only means to develop a ground system. Install a large number of radials, laid straight, but not too taut. The portions not in contact with the rock are in

A facility that is down for even 5 min can suffer a significant loss of productivity or data that may take hours or days to rebuild. A blackout affecting a transportation or medical center could be life-threatening. Coupled with this threat is the possibility of extended power-service loss due to severe storm conditions. Many broadcast

A more sophisticated power-control system is shown in Figure 1, where a dual feeder supply is coupled with a motor-generator set to provide clean, undisturbed ac power to the load. The m-g set will smooth over the transition from the main utility feed to the standby, often making a commercial power failure unnoticed by on-site

Engine-generator sets are available for power levels ranging from less than 1 kVA to several thousand kVA or more. Machines also can be paralleled to provide greater capacity. Engine-generator sets typically are classified by the type of power plant used: • Diesel: Advantages: rugged and dependable, low fuel costs, low fire or explosion hazard. Disadvantages:

Generators for standby power applications can be induction or synchronous machines. Most engine-generator systems in use today are of the synchronous type because of the versatility, reliability, and capability of operating independently that this approach provides. Most modern synchronous generators are of the revolving field alternator design. Essentially, this means that the armature windings are

An uninterruptible power system is an elegant solution to power outage concerns. The output of the UPS inverter can be a sine wave or pseudo sine wave. When shopping for a UPS system, consider the following: • Power reserve capacity for future growth of the facility. • Inverter current surge capability (if the system will