Limitation and application of High Voltage DC (HVDC)
Limitation and application of High Voltage DC (HVDC) :
Limitation:- 1) It is difficult to step up and step down DC voltage like AC voltage. 2) Special cooling arrangements are necessary for converter, so it increases cost of substation. 3) Cost of DC substation is more than AC substation, due to additional equipment required like rectifier, inverter etc. 4) Maintenance cost of DC substation is more due to additional equipment. 5) Space required for DC substation is more due to additional equipment 6) Losses in DC substation are more due to additional equipment. 7) Over load capacity Converter is very less. 8) Reliable DC circuit breakers are not available like AC circuit breakers. 9) Cost of DC circuit breaker is more than AC circuit breaker. 10) Converters consumes reactive power 11) Generation of harmonics. 12)If ground is used as the return path, then it leads Corrosion of underground metallic structure of buildings, pipes, etc. due to chemical action. Causes disturbance in underground communication cable. 13) HVDC is not economical for short distance transmission because termination cost equipment is more.
Application of High Voltage DC (HVDC):
1) HVDC is economical to transmit bulk amount of power 1000 MW & above. Over a long distance 800 Km & above 2) Interconnection of two transmission lines having different frequencies is possible through HVDC link. 3) HVDC is preferred for underground cable when power transmission through underground cable is greater than 40-50 KM than only HVDC uniquely suited. 4) HVDC is preferred for underground cable transmission as incoming line in megacities. ./ City centre in- feed. 5) HVDC is preferred for underground cable transmission for crossing long lake, ocean etc. 6) HVDC is preferred for underground cable transmission where atmospheric conditions are too bad for overhead transmission line, e.g. High wind pressure, rainfall, icefall etc. 7) HVDC is preferred for underground cable for long distance underwater power links. 8) HVDC is preferred for underground cable for powering island from onshore. 9) HVDC is preferred for underground cable for taking power from offshore wind farm. 10) HVDC is preferred for underground cable for powering oil and gas offshore floating platform. 11) Integration of generation( conventional/non-conventional) 12) Increasing existing grid utilization. 13) Interconnection of different grids or networks