Resistance & Reactance Grounding

Resistance grounding In this type of  neutral grounding, the neutral of the system is connected to ground through one or more resistance. Resistance grounding limits the fault currents. It protects the system from transient overvoltages. Resistance grounding decreases the arcing grounding risk and permits ground-fault protection. The value of resistance used in the neutral grounding …

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Types of Electrical Insulator

Overhead line insulators are used to separate line conductors from each other and the supporting structures electrically. Permittivity and dielectric strength of the insulating material are very high so that it can withstand high electrical stress. Insulators protect the transmission line from overvoltages which occur due to lightning,  switching, or other causes under the severe …

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Tap-changing Transformers

The change of voltage is affected by changing the numbers of turns of the transformer provided with taps. For sufficiently close control of voltage, taps are usually provided on the high voltage windings of the transformer. There are two types of tap-changing transformers Off-load tap changing transformer On-load tap changing transformer Off-load tap-changing transformer In …

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Overvoltage Protection

When the voltage in a system, raised beyond its rated voltage, then it is known as overvoltage. This overvoltage may be of transient or persistent nature. The main cause due to which overvoltage is produced in the power system may be conveniently grouped into two categories, namely, internal and external. Internal overvoltage has got their …

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Power Factor

The power factor is defined as the ratio of the active power (P) and volt-amperes. The active power is the real power which is assumed in an AC circuit, whereas volt-amperes is the apparent power which is produced in the circuit when the waves of voltage or current are not in phase. For sinusoidal waveforms, …

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Power Factor Improvement

If the power factor is low or poor, it is necessary to improve or correct it. It may be improved by injecting a leading current into the circuit so as to neutralize the effect of lagging current. The power factor may be improved by using static capacitors or synchronous motors. Power factor correction by static …

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Solid Grounding

A power system is said to be effectively grounded or solidly grounded when the neutral of a generator, power transformer or grounding transformer are directly connected to the ground through a conductor of negligible resistance and reactance. A part of a system or system is said to be solidly grounded when the positive-sequence impedance of …

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Calculation of Sag & Tension

Calculation of sag and tension in transmission line depend on the span of the conductor. Span having equal level supports is called level span, whereas when the level of the supports is not at an equal level is known as unequal level span. The calculation of conductor at an equal level shown below. Consider a …

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Sag and Tension

For safety purpose, the ground clearance of the conductors at maximum temperature and minimum loading condition should be maintained. Analysis of the sag and tension is important in the transmission line for the continuity and quality of electrical services. If the tension of the conductor is increased beyond the limit, it may get broken, and …

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Swing Equation

The transient stability of the system can be determined by the help of the swing equation. Let θ be the angular position of the rotor at any instant t. θ  is continuously changing with time, and it is convenient to measure it with respect to the reference axis shown in the figure below. The angular position …

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