In the following article you will find a brief summary of the differences between various HV transmission technologies. In addition, sailint techno-economic characteristics of each of them are presented.

https://www.researchgate.net/publication/320686188_Sizing_and_Operational_Loading_of_Reactive_Power_Compensators_for_Grid_Connected_Wind_Farms_Considering_Various_Transmission_Options?_iepl%5BviewId%5D=hoXEhogIp2TkcttA5z2kehm0&_iepl%5BprofilePublicationItemVariant%5D=default&_iepl%5Bcontexts%5D%5B0%5D=prfpi&_iepl%5BtargetEntityId%5D=PB%3A320686188&_iepl%5BinteractionType%5D=publicationTitle

http://new.abb.com/systems/hvdc/why-hvdc

http://www.electricaleasy.com/2016/02/hvdc-vs-hvac.html

http://electrical-engineering-portal.com/advantages-of-hvdc-over-hvac-transmission

some further comparisons from experts. I am a chemist, I only remember when I worked at the Furukawa Electric Institute of Technology in Hungary, we investiaged both HVAC and HVDC cable insulation materials - so both are useful in their respecive areas.

Adding to the colleagues above, High voltage transmission either AC or DC is necessary for reducing the conducting metallic wire size and thereby render electric power transmission feasible. In addition, for the same power as we decrease the current by increasing the transmission voltage , the ohmic losses will decrease appreciably as it proportional to the magnitude square of the current.

The generated electric power is AC so one needs to raise its voltage for transmission by electric transformers. Transmitting the AC current, in addition to the ohmic voltage drop there will be voltage drop on the reactive parts of the transmission line. This is one of the main problems of AC transmission. So, one has to boost the voltage regularly in long distance transmission lines.

The voltage fading of the AC on the transmission line motivated the use of DC transmission where the there is only ohmic voltage drop and there is no reactive voltage drop and therefore, one can transmit the electrical power for much longer distance without boosting specially if one even uses super high voltage transmission.

However there are some other requirements to realize the DC transmission,

One has to convert the AC to DC at the start of transmission and back convert the DC to AC at the end of transmission since the both the generation and distribution are AC.

These conversion stations became feasible with the the state of the art solid power devices. Precise comparisons can be found in the literature brought by the colleges above.

I only introduced an outline about a conceptual comparison.

Best wishes

Thank you very much for sharing your experience. I hope you will continue your help so that other researcher especially young researcher will get benefit from your knowledge and expertise.

Many thanks for answering this question.

It is OK Obaid. You are welcome