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HVDC & FACTS

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Mainly this presentation focuses on the comparison between HVDC and FACTS...

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HVDC & FACTS

  1. 1. Presented by: Pooja Bisi Pravudatta Patel Pritesh Priyadarshi Priti Sucharita Tripathy
  2. 2. CONTENTS Introduction of HVDC Advantages and disadvantages of HVDC Introduction of FACTS Technology Advantages of FACTS technology Comparison of HVDC and FACTS
  3. 3. HVDC 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 The longest HVDC link in the world is currently the Xiangjiaba– Shanghai 2,071 km HVDC allows power transmission between unsynchronized AC transmission systems For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses. An HVDC link can be controlled independently of the phase angle between source and load, it can stabilize a network against disturbances due to rapid changes in power. Various HVDC links in INDIA are: ± 500 kV , 1500 MWRihand – Delhi HVDC,814km ± 500 kV ,2000MW, HVDC Talchar – Kolar Transmission Link, 1450km
  4. 4. CONVERTERS •Perform AC to DC and DC to AC conversion •HVDC converters are usually built as 12-pulse circuits. •Consist of valve bridges and transformer SMOOTHING REACTORS •High reactors with inductance as high as 1H in series with each pole. •Decrease harmonics in voltage and current in dc lines. •Prevent commutation failure in inverter. HARMONIC FILTERS •Converter generates harmonics in voltages and currents .These harmonics may cause overheating of capacitors and nearby generators and interference with Telecommunication systems, harmonic filters is used to mitigate these harmonics. REACTIVE POWER SUPPLIER •Under steady state condition, the reactive power consumed by the converter is about 50% of the active power transferred. •Under transient conditions it could be much higher. •For a strong AC power system, this reactive power is provided by a shunt capacitor. ELECTRODES •Electrodes are conductors that provide connection to the earth for neutral and they have large surface to minimse current and surface voltage gradients.
  5. 5. DC LINES: •They may be overhead lines or cables. •DC lines are very similar to AC lines. AC CIRCUIT BREAKER: •They used to clear the faults in transformer and for taking DC link out of service.
  6. 6. MONOPOLAR LINK BIPOLAR LINK HOMOPOLAR LINK MONOPOLAR LINK: •One pole, one set of conductor for transmission and current return path is through earth. •Mainly used for submarine cable transmission
  7. 7. BIPOLAR LINK: •Two poles, two set of conductors in transmission line, one positive with respect to earth & other negative. •The mid point of Bi-poles in each terminal is earthed via an electrode line and earth electrode. •In normal condition power flows through lines & negligible current through earth electrode. (in order of less than 10 Amps.)
  8. 8. BACK TO BACK HVDC LINK: •Usually bipolar without earth return. •Converter & inverters are located at the same place. •No HVDC Transmission line. •Provides Asynchronous tie between two different AC network •Power transfer can be in either direction •Chandrapur, connection between western to eastern region
  9. 9. MULTI-TERMINAL SYSTEM •Three or more terminals connected in parallel, some feed power and some receive power from HVDC Bus. •Provides Inter connection among three or more AC network.
  10. 10. Advantages Of HVDC Technical advantages: No requirement of reactive power Practical absence of transmission line length limitations No system stability problems Interconnection of asynchronously operated power systems No production of charging current No increase of short circuit power at the connection point
  11. 11. Independent control of AC systems Fast change of energy flow i.e. Ability of quick and bidirectional control of energy flow Lesser corona loss and radio interference Greater reliability Increase of transmission capacity Can be used for submarine and underground transmission
  12. 12. Economic Advantages: Low cost of DC lines and cables Simple in construction Low cost for insulators and towers Less Line losses Transmission line can be built in stages
  13. 13. Disadvantages Of HVDC Use of converters ,filters etc increases the overall cost DC circuit breakers are more expensive HVDC converters have low overloading capacity More maintenance is required for insulators Voltage transformation is possible only on AC side
  14. 14. Definition of “Facts” & “Facts Controller”:  FACTS:(IEEE Definition) Alternating current transmission systems incorporating power electronic-based and other static controllers to enhance controllability and increase power transfer capability.  FACTS Controller: A power electronic-based system and other static equipment that provide control of one or more AC transmission system parameters.
  15. 15. Basic Types of FACTS Controllers FACTS controllers are classified as Series Controllers Shunt Controllers Combined Series-Series Controllers Combined Series-Shunt Controllers General Symbol of FACTS controller
  16. 16. Advantages of FACTS technology:  Control of power flow to ensure optimum power flow.  Increase the loading capability of of lines to their thermal capabilities, including short term and seasonal. This can be achieved by overcoming other limitations, and sharing power among lines according to their capability.  Increase the system security by raising the transient stability limit.  Provides greater flexibility in siting new generation.  Reduce reactive power flows, thus allowing the lines to carry more active power.
  17. 17. ADVANTAGES OF HVDC OVER HVAC USING FACTS TRANSMISSION CONTROLLED POWER ASYNCHRONOUS OPERATION POSSIBLE BETWEEN REGIONS HAVING DIFFERENT ELECTRICAL PARAMETERS(I.E FREQUENCY) NO RESTRICTION ON LINE LENGTH AS NO REACTANCE IN DC LINES
  18. 18. LONG DISTANCE OVERHEAD TRANSMISSION: • If the overhead transmission is long enough, say 1500 Km, the saving in capital costs and losses with a dc transmission line may be enough to pay for two converters. This distance is known as break-even distance. • This break-even distance is very subject to many factors including the cost of the line, right-of-way, and often most important the politics of obtaining permission to build the line. • But it is important to recognize that while FACTS can play an important role in an effective use of ac transmission, it probably does not have too much influence on the break-even distance.
  19. 19. COST: AC vs DC Transmission Line Cost AC Line Cost DC Terminal Cost DC Terminal Cost AC Break Even Distance
  20. 20. HVDC IN INDIA Back-to-Back HVDC LINK CONNECTING REGION CAPACITY (MW) Vindyachal North –West 2 x 250 Chandrapur West – South 2 x 500 Vizag – I East – South 500 Sasaram East – North 500 Vizag – II East – South 500
  21. 21. 1)Both are complementary technologies 2)The role of HVDC is to interconnect ac systems where a reliable ac interconnectionwould be too expensive  Independent frequency and control  Lower line cost  Power control, voltage control and stability control possible 3) The large market potential for FACTS is within AC system on a value added basis where  The existing steady-state phase angle between bus node is reasonable  The cost of FACTS solution is lower than the HVDC cost  The required FACTS controller capacity is lesser than the transmission rating
  22. 22. FACTS IN INDIA In india,FACTS has received much attention in the last 2 decades The 1st FACTS device installed in india is Thyrister Controlled Series Capacitor(TCSC) with Fixed Series Compensation(FSC) at 400 KV transmission line between Kanpur(UP) and Ballabgarh(Haryana) in the Northern grid. Some more existing FACTS devices projects which work succesfully in india are :  Ranchi-Sipat 400 KV D/C  376 Km transmission line with 40% FSC at Ranchi end  364 Km transmission line in Andra pradesh  FSC-TCSC installed in Kalpakam-Khammam 400 KV D/C
  23. 23. HVDC PROJECTS: APPLICATIONS SUBMARINE CABLES: Cables have a large capacitance and hence ac cables require a large charging current (reactive power) an order of magnitude larger than that of overhead lines. As a result, for over a 30 Km or so stretch of ac submarine cable, the charging current supplied from the shore will fully load the cable and leave no room for transmitting real power. The charging current flowing in the cables can only be reduced by connecting shunt inductors to the cable at an intervals of 15-20 Km. But with HVDC cable, distance is not a technical barrier and also the cost of dc cable transmission is much lower than that of ac. FACTS technology can provide an improvement by controlling the magnitude of one end of the voltages so as to keep it identical to that of the other one. In this way, the effective length of the cable from the standpoint of the charging current can be halved.
  24. 24. UNDERGROUND TRANSMISSION: •Because of the high cost of underground cables, the break-even distance for HVDC is more like 100 Km as against 1500 Km for overhead lines. •Again FACTS technology probably does not have much influence in the break-even distance.
  25. 25. CONNECTING AC SYSTEMS OF DIFFERENT OR INCOMPATIBLE FREQUENCIES: •For historical reasons, the oceans in effect separate the globe’s electric systems into 50 Hz and 60 Hz groups. •The 60 Hz normal frequency pervades all the countries of the Americas, excepting Argentina and Paraguay. Those two countries and all the rest of the world have a 50 Hz frequency except Japan, which is partly 50 Hz and 60 Hz. •In general, the oceans are too huge and deep to justify interconnections of 50 Hz and 60 Hz systems. Thus, there is a limited market for HVDC for connecting 50 and 60 Hz systems.

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