# Power Engineering definition

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Electrical power Engineering mainly involves generation of high voltage power and transmission of that power over long distance. For this , a power plant or substation is required, where a generator converts other forms of energy into electrical energy. Then the power is transmitted over long distance by using transformers and power cables. Transformers are used in order to step up the voltage further and reduce power losses in the transmission conductors. At the receiving station the high voltages is stepped down and distributed to commercial or domestic area. The reason for using high voltages in transmission line is that the power loss is minimized. As the voltage is high the current is low, which we know from power equation. Power loss is nothing but resistance multiplied by current squared. Electrical machinery such as motor , generator, refrigerator are designed using electrical power engineering concepts.Electrical motor and generator are each other's reciprocal or inverse if we consider their principle of operation . The reverse operation of motor turns it into a generator. An important factor in power system stability is the swing equation. It describes the rotor swing under under any disturbance of the system A stable power system always remain synchronous with its internal component and relative position between rotor and resultant magnetic flux remains fixed. But transient state arises when generator normal operation is thwarted. Swing equation is applied in such situation to analyze the system. The electircal torque equals the mechanical torques under normal condition and net acceleration becomes zero. This is the condition assumming that internal losses are zero.

**Fig: Swing equation**

But when there is relative speed between rotor and stator field, acceleration develops. Net torque is the double derivative of angle of rotor with respect to a stationary axis. Swing equation is a second order non-linear inhomogeneous differential equation. It contains first derivative of omega(w) or second derivative of torque angle (delta). Tesla contributed greatly to the development of ac machinery . He even thought of transferring high voltage electricity over long distance without using wire. But unfortunately he did not succeed in that. Today although power transmission occurs over long area , the amount of power is very small compared to that Tesla envisioned. As an example mobile or cellular communication involve transmission of signal which power is very small (i.e pico watt ). Power engineering is also concerned about protection and safety of equipment during operation of any system like power station or transmission of power. So switch gear and protection is utilized in all the power systems. This guarantees the safety of electrical equipments. Switch gear consists of various magnetic relays, switches, capacitors, sensors and many other components. Power system analysis is a subject which incorporates linear algebra and calculus.

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