HVDC Transmission Advantage and Disadvantage
Advantage of HVDC Transmission
1. Reactive power RequiredA HVDC line neither generate more preserver reactive power . the converter at the two end draw some reactive power from A.C system for their operation . This reactive power varies with the transmitted power but is that for independent of line length. It is found that for lines greater than 400KM length. A DC line requires less reactive
power than lines.
2. System stabilityTwo separate AC system interconnected by the AC line must operate with two separate AC system interconnected by a DC link may operate asynchronously may even operate at different frequency.
3. Independent control of AC systemThe AC system interconnected by a DC line can be controlled independently . they can be complexly independent as regard system frequency, system control, short circuit rating, future expansion etc.
4. Grater ReliabilityA two conductor by polar DC line is more relible than a thrre conductor three phase line because in the event of a fault on one conductor , the other conductor of the DC line continue to operate with ground return where as three phase AC line can not operate on two phase.
5. Tower size and costThe phase to phase clearness and phase to ground clearance are smaller for DC transmission as compared to equivalent AC transmission line for
same power and distance .
6. Power factorLine power factor always unity .
7. Less costA basic DC line less costly compared with three phase AC line because only two conductor are needed in DC line com paired with in AC line.
8. Ground returnGround can be used as a return conductor in case of DC system.
9. No skin effectThe skin effect is absent in DC line resulting in uniform current density in conductor and hence efficient utilization of conductor cross sectional area.
10. Lesser corona loss and radio interferenceThe corona loss and radio interference is less in DC line as compaired to AC line of same conductor diameter and voltage in bad weather .
11. No comparison requiredNo service or shunt compensation is required for long distance DC line.
12. Fast change of energy flowThe quick control of converter values permit fast changes in megnitude and direction of energy flow when required this result in increased in limits of transient stability cordination of system control at two ends.
13. No change in currentContinuous line charging current are absent in HVDC over head line and cables.
14. Longer life of cablesDielectric fatigue is absent i DC so that insulation has longer life
Disadvantage of HVDC line
A part from many advantages of HVDC transmission there are some disadvanteges also which are is follows