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**Jawaharlal Nehru Technological University Anantapur (JNTU) College of Engineering (CEP), Pulivendula, Pulivendula, Andhra Pradesh, India - JNTUACEP**- Electrical Engineering
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Conclusion: By the end of this unit one can understand the basic parameters to form electrical network, formation of electrical network, simplifying the network using different reduction techniques to determine voltage, current and power in the network.

UNIT 2 INTRODUCTION: In general transmission of Dc power is difficult and not economical and even Dc generation is also less , hence more units are required to meet demand to overcome above drawbacks the AC generation came into existence , therefore before going to study in depth about Ac generation, transmission and distribution it is necessary to have the knowledge of alternating quantities and their importance in power systems. Alternating Quantity: In the definition alternating quantity is one whose value changes from time to time , if this change periodically happens then it is called as periodic alternating quantity otherwise nonperiodic alternating quantity. There are many periodic functions but best one sinusoidal function. Hence generally sine function is used to represent periodic waveform because of following reasons, It can be easily generated. Integration and differentiation of sine function is again sine function only. Hence we shall study what is sine function?, representation of sine function, definitions related sine functions and its applicability in power system networks. Some of the definitions related to sine wave are peak value, peak to peak value, average value, RMS value, peak factor and form factor. AC Circuit: An AC circuit consists of an source, RLC elements and connecting wire, here AC source could be an alternating voltage source or alternating current source. Before formation of AC circuit one should have the knowledge of reactance, impedance, susceptance and admittance offered by R-L-C parameters. In the definitions :

Impedance is the ratio of source voltage to source current for the circuit and for the element ratio of voltage across element to current flowing through element. Impedance is analogues to resistance in DC circuits. Admittance is reciprocal of impedance in definition and is analogues to conductance in Dc circuit. Power In AC Circuit: In the Dc circuits the power is given as product of voltage and current but the case is different in AC circuit. The behavior of AC circuit studied in terms of reactance, resistance and impedance offered by the circuit. Depending on this behavior the Ac circuit is associated with three powers , they are—active , reactive and apparent power. Active power – because of resistive nature of circuit. Reactive power -- because of reactance nature of circuit. Apparent power – represented by impedance of circuit. But the only usefull power by the load always active power, that is why it is also called as true power, average power , ohmic power and active power. The power concept can be easily understood by power triangle Where, A – active power B C B -- reactive power C – apparent power A In the similar fashion impedance triangle can also be represented Where, A – resistance B C B -- reactance C – impedance A

CONCLUSION: By the end of this unit student will be able to understand what is AC quantity?, representation elements in AC circuit, what are the AC sources?, how to represent Ac circuit?, what is the behavior of AC circuit? And how it is applicable to real power systems?

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