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The most commonly used protective device in a distribution circuit is the fuse. Fuse characteristics vary considerably from one manufacturer to another and the specifics must be obtained from their appropriate literature. Figure 3.3 shows the time-current characteristics which consist of the minimum melt and total clearing curves. FIGURE 3.3 Fuse time-current characteristic. Minimum melt […]

The main protection system for a given zone of protection is called the primary protection system. It operates in the fastest time possible and removes the least amount of equipment from service. On Extra High Voltage (EHV) systems, i.e., 345kV and above, it is common to use duplicate primary protection systems in case a component

It is, of course, desirable to remove a fault from the power system as quickly as possible. However, the relay must make its decision based upon voltage and current waveforms, which are severely distorted due to transient phenomena that follow the occurrence of a fault. The relay must separate the meaningful and significant information contained

Any number of conditions has been the reason for an electrical transformer failure. Statistics show that winding failures most frequently cause transformer faults (ANSI/IEEE, 1985). Insulation deterioration, often the result of moisture, overheating, vibration, voltage surges, and mechanical stress created during transformer through faults, is the major reason for winding failure. Voltage regulating load tap

COSTS AND BENEFITS OF SAFETY PROGRAMS Organizational focus on employee safety can provide for higher morale and productivity in the workplace. This is due to the perception that the company truly cares about the health and well-being of its employees, thus creating a sense of pride for the organization. Increased productivity as it correlates to

In any occupation, a level of risk can always be expected while on the job. Some occupations are obviously more dangerous than others, and for many years, the power industry had a reputation of being one of the most hazardous workplace environments. The industry has worked hard to eliminate this reputation, and today it is

When we hear the term solar energy,” we usually think of heat from the sun’s rays which can be put to work. But there are other forms of solar energy. Just as hydropower is a form of solar energy, so too is windpower. In effect, the sun causes the wind to blow by heating air

Demands for power vary greatly during the day and night. These demands vary considerably from season to season, as well. For example, the highest peaks are usually found during summer daylight hours when air conditioners are running. Nuclear and fossil fuel plants are not efficient for producing power for the short periods of increased demand

A serious issue that must be addressed is how and where to use the electric power generated by extracting energy from the tides. Tides are cyclical by their nature, and the corresponding power output of a tidal power plant does not always coincide with the peak of human activity. In countries with a well-developed power

Some General precautions should be observed in electrical measurements, and sources of error should be avoided, as detailed below: 1. The accuracy limits of the instruments, standards, and methods used should be known so that appropriate choice of these measuring elements may be made. It should be noted that instrument accuracy classes state the “initial”