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High Voltage Direct Current(Hvdc) transmission

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this presentation is prepared my friend about high voltage direct current that is very important in electrical engineering.

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High Voltage Direct Current(Hvdc) transmission

  1. 1. AAMIR SOHAIL 12063122-025 SECTION(B) SEMESTER 5TH University of Gujrat (Pakistan)
  2. 2.  HVDC Definition.  Introduction to HVDC.  HVDC working.  HVDC transmission principle.  HVAC transmission principle.  Comparison of HVAC & HVDC.  Advantages & Disadvantages of HVDC.
  3. 3.  HVDC stands for high voltage direct current transmission.  A high-voltage, direct current (HVDC) electric power transmission system uses direct current for the bulk transmission of electrical power, in contrast with the more common alternating current (AC) systems
  4. 4.  First commercial application of HVDC between Swedish mainland and the island of Gotland in 1954.  Underwater link of 90 km and 20 MW.  After the advent of thyristor convertor, New Brunswick and Quebec 320 MW back-to-back DC interconnection commissioned in 1972.
  5. 5.  With reduced size, cost and improved reliability of power electronic converters, has made HVDC transmission more widespread.  In North America, total HVDC transmission capacity in 1987 was 14,000 MW
  6. 6.  AC Transmission Principle
  7. 7.  HVDC Transmission Principle
  8. 8. CONVENTIONALLY POWER TRANSMISSION IS EFFECTED THROUGH HVAC SYSTEMS ALL OVER THE WORLD.  HVAC TRANSMISSION IS HAVING SEVER LIMITATIONS LIKE LINE LENGTH , UNCONTROLLED POWER FLOW, OVER/LOW VOLTAGES DURING LIGHTLY / OVER LOADED CONDITIONS,STABILITY PROBLEMS,FAULT ISOLATION ETC
  9. 9.  HVDC Use less current  DC roll along the line , opposing force friction.  AC current will struggle against inertia in the line (100times/sec)- current inertia –inductance- reactive power
  10. 10.  Better Voltage utilization rating
  11. 11.  DC has Greater Reach.  Distance as well as amount of POWER determine the choice of DC over AC.
  12. 12.  DC conserves Forest and saves land.  Fewer support TOWER, less losses.
  13. 13. Line controlled power flow is possible very precisely. ASYNCHRONUS OPERATION possible between regions having different ELECTRICAL parameters.  No restriction on line length as no reactance in DC.
  14. 14. Stabilizing HVAC SYSTEMS –Dampening of power swings and sub synchronous frequencies of GENERATOR. Faults in one AC system will not effect the other AC system . Cable transmission.
  15. 15.  Cheaper than HVAC SYSTEM due to less TRANSMISSION LINES & LESS RIGHT OF WAY for the same amount of power transmission.
  16. 16.  If DC is required to be used for transmission since our primary source of power is A.C, the following are the basic steps: 1. CONVERT AC into DC (rectifier) 2. TRANSMIT DC 3. CONVERT DC into AC ( inverter)
  17. 17.  Due to ease of transformation of voltage levels (simple transformer action) and rugged squirrel cage motors, ALTERNATING CURRENT is universally utilized.— Both for GENERATION and LOADS and hence for TRANSMISSION.  Generators are at remote places, away from the populated areas i.e. the load centers  They are either PIT HEAD THERMAL or HYDEL
  18. 18.  Turbines drive synchronous generators giving an output at 15- 25 kV.  Voltage is boosted up to 220 or 400 KV by step-up transformers for transmission to LOADS.  To reach the loads at homes/industry at required safe levels, transformers step down voltage
  19. 19.  In a number of applications HVDC is more effective than AC transmission.  Undersea cables, where high capacitance causes additional AC losses. (e.g. 250 km Baltic Cable between Sweden and Germany)  Long power transmission without intermediate taps, for example, in remote areas  Power transmission and stabilization between unsynchronized AC distribution systems
  20. 20.  Connecting a remote generating plant to the distribution grid  Reducing line cost: 1) fewer conductors 2) thinner conductors since HVDC does not suffer from the skin effect  Facilitate power transmission between different countries that use AC at differing voltages and/or frequencies  Synchronize AC produced by renewable energy sources
  21. 21.  The disadvantages of HVDC are in conversion, switching and control.  Expensive inverters with limited overload capacity.  Higher losses in static inverters at smaller transmission distances.
  22. 22.  The cost of the inverters may not be offset by reductions in line construction cost and lower line loss.  High voltage DC circuit breakers are difficult to build because some mechanism must be included in the circuit breaker to force current to zero, otherwise arcing and contact wear would be too great to allow reliable switching.
  23. 23.  Costs vary widely depending on power rating, circuit length, overhead vs. underwater route, land costs, and AC network improvements required at either terminal.

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