short transmission line

among 3 types of transmission lines here is one of them-short transmission line with its classification and phasor diagram

1. ELECTRICAL POWER SYSTEM - II SHORT TRANSMISSION LINE PREPARED BY :- (BATCH B – 3) SHAH MOHIL ARUNBHAI 13028010910 2 SHAH NEEL GIRISHKUMAR 130280109103 SUHAGIYA SAUMIL ASHOKBHAI 130280109111

2. Contents Introduction Representation of transmission line Classification Short transmission line Phasor diagrams References

3. Introduction Electrical power is generated in power station. It is necessary to send this power to different areas. A conductive line which is used for the transmission of the electrical power from one place to another is known as “Transmission Line”.

4. Representation of transmission line

5. Classification Transmission lines are generally classified as follows: 1) Short transmission line 2) Medium transmission line 3) Long transmission line

6. Short transmission line Transmission line having length less than 80 km and operating voltage less than 20 kV are generally known as Short transmission line. Due to small distance and low voltage capacitance effect is negligible. Hence performance of these lines depend upon resistance and inductance only.

7. Short transmission line The equivalent circuit of a short transmission line is shown in Fig., where Is and I R are the sending and receiving end currents, respectively, and Vs and V R are the sending and receiving end line-to-neutral voltages. The circuit is solved as a simple series AC circuit. So, where Z is zl, the total series impedance of the line .

8. Short transmission line

9. Short transmission line The effect of the variation of the power factor of the load on the voltage regulation of a line is most easily understood for the short line and therefore will be considered at this time. Voltage regulation of a transmission line is the rise in voltage at the receiving end, expressed in percent of full-load voltage, when full load at a specified power factor is removed while the sending-end voltage is held constant.

10. Short transmission line Corresponding to Eq. we can write, where | Vnl | is the magnitude of receiving-end voltage at no load and | Vfl | is the magnitude of receiving-end voltage at full load with | Vs | constant . After the load on a short transmission line , represented by the circuit of Fig., is removed, the voltage at the receiving end is equal to the voltage at the sending end .

11. Short transmission line In Fig., with the load connected , the receiving-end voltage is designated by VR , and | VR | = | Vfl |. The sending-end voltage is Vs ; and | Vs | = | Vnl |.

12. Phasor diagrams (a) Load p.f.=70% lag (b) Load p.f.=100% (c) Load p.f.=70% lead

13. Phasor diagrams The phasor diagrams of Fig. are drawn for the same magnitudes of the receiving end voltage and current and show that a larger value of the sending-end voltage is required to maintain a given receiving-end voltage when the receiving- end current is lagging the voltage than when the same current and voltage are in phase. A still smaller sending-end voltage is required to maintain the given receiving-end voltage when the receiving-end current leads the voltage.

14. Phasor diagrams The voltage drop is the same in the series impedance of the line in all cases; because of the different power factors, however, the voltage drop is added to the receiving - end voltage at a different angle in each case. The regulation is greatest for lagging power factors and least, or even negative, for leading power factors. The inductive reactance of (transmission line is larger than the resistance, and the principle of regulation illustrated in Fig . is true for any load supplied by a predominantly inductive circuit .

15. Phasor diagrams The magnitudes of the voltage drops IrR and IlXl for a short line have been exaggerated with respect to Vr in drawing the phasor diagrams in order to illustrate the point more clearl y. The relation between power factor and regulation for longer lines is similar to that for short lines but is not visualized so easily.

16. References Elements of power system analysis by W. D. Stevenson Power system analysis by Grainger & Stevenson Modern power system analysis by Nagrath & Kothari Wikipedia

17. Thank You