Power system contingencies


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This presentation talks about the power system and its contingencies in real world and how it is dealt.

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Power system contingencies

  1. 1. Seminar On Power System Contingencies
  2. 2. Power System  Power System voltage control has a hierarchy structure with three levels: the primary, secondary, and the tertiary voltage control. Over the past 20 yrs, one of the most successful measures proposed to improve Power System voltage regulation has been the application of secondary voltage control, initiated by the French Electricity Company.
  3. 3. Important Of Features Power System           Flickers Harmonics Interruption Long Lines Long Cables Loop Flow Reactive Power Sags & Swells Unbalanced Load Voltage Instability
  4. 4. Flickers A fluctuation in system voltage that can lead to noticeable changes in light output.  Voltage Flicker can either be a periodic or non-periodic fluctuation in voltage magnitude i.e. the fluctuation may occur continuously at regular intervals or only on occasions.
  5. 5. How To Reduce Flickers  Installation of a MiniCap to reduce flicker during large motor starting .  Minicap is nothing but the Installation of the feeder strengthens the network . a series capacitor in
  6. 6. Benefits •Reduced voltage fluctuations (flicker) •Improved voltage profile along the line •Easier starting of large motors •Self-regulation
  7. 7. Harmonics  Harmonics are associated with steady-state waveform distortion of currents and voltages.  Harmonics are components that make up a waveform where each component has a frequency that is an integral multiple of the fundamental frequency. The term Harmonic is normally applied to waveform components that have frequencies other than the fundamental frequency. For a 50 Hz or 60Hz system the fundamental frequency is 50HZ or 60Hz. A waveform that contains any components other than the fundamental frequency is nonsinusoidal and considered to be distorted.
  8. 8. How To Reduce Harmonics  Installing filters near the harmonic sources can effectively reduce harmonics.
  9. 9. Benefits  Eliminates harmonics.  Improved Power Factor.  Reduced Transmission Losses.  Increased Transmission Capability.  Improved Voltage Control.  Improved Power Quality.
  10. 10. Interruptions • Occur when the supply voltage drops below 10% of the nominal value.  An interruption is usually caused by downstream faults that are cleared by breakers or fuses. A sustained interruption is caused by upstream breaker or fuse operation. Upstream breakers may operate due to short-circuits, overloads, and loss of stability on the bulk power system.
  11. 11. Long Lines  Long lines need special consideration in the planning of a power system.  For long AC lines one must consider i.e. the reactive power compensation, the transient stability and switching over voltages and how many intermediate substations one needs.
  12. 12. Area of application:-Expressway for power  A HVDC transmission line costs less than an AC line for the same transmission capacity.
  13. 13. Benefits  Lower investment cost  Lower losses  Lower right-of-way requirement for DC lines than for AC lines  HVDC does not contribute to the short circuit current
  14. 14. Long cables  Basically Long cables are of two types  Submarine Cables  Under Ground Cables
  15. 15. Submarine Cables Application  Submarine Cables are used for long distance water crossing.
  16. 16. Benefits  Lower investment cost  Lower losses
  17. 17. Loop flow • Unscheduled power flow on a given transmission path in an interconnected electrical system. • Unscheduled power flows on transmission lines or facilities may result in a violation of reliability criteria and decrease available transfer capability between neighbouring control areas or utility systems.
  18. 18. Area of application: Interconnected power systems Benefits  HVDC can be controlled to transmit contracted amounts of power and alleviate unwanted loop flows.  An HVDC link can alternatively be controlled to minimize total network losses  An HVDC link can never be overloaded
  19. 19. Reactive Power Factor • Reactive power is defined as the product of the r.m.s. voltage, current, and the sine of the difference in phase angle between the two. • To maintain efficient transmission and distribution, it is necessary to improve the reactive power factor.
  20. 20. How to Improve power factor • The use of the MiniCap on a distribution feeder provides self-regulated reactive power for improved power factor at the utility source.
  21. 21. Benefits  Increased power factor at the utility source.  Easier starting of large motors .  Improved voltage regulation and reactive power balance.  Self-regulation Improved power factor, Reduced transmission losses, Increased transmission capability.  Improved voltage control, Improved power quality, Eliminates harmonics S.
  22. 22. Sags & Swells  Short duration decrease/increase (sag/swell) in supply voltage.  Voltage sags are one of the most commonly occurring power quality problems. They are usually generated inside a facility but may also be a result of a momentary voltage drop in the distribution supply.  Electronic equipment is usually the main victim of sags, as they do not contain sufficient internal energy to ‘ride through’ the disturbance.
  23. 23. Voltage Instability • Post-disturbance excursions of voltages at some buses in the power system out of the steady operation region. • Voltage instability is basically caused by an unavailability of reactive power support in an area of the network, where the voltage drops uncontrollably.
  24. 24. Unbalanced Load • A load which does not draw balanced current from a balanced three-phases supply.  A single-phase load, since it does not draw a balanced threephase current, will create unequal voltage drops across the series impedances of the delivery system.
  25. 25. Area of application:-Railway Feeder connected to the Public Grid Modern electric rail system is a major source of unbalanced loads.  STATCOM can elegantly be used to restore voltage and current balance in the grid, and to mitigate voltage fluctuations generated by the traction loads. 
  26. 26. Benefits  Voltage Balancing  Harmonic Filtering  Power Factor Correction Other applications:  Power Quality Improvement, Flicker Mitigation  Grid Voltage Support
  27. 27. Summary  The new electricity supply industry presents increasing challenges for stable and secure operation of power systems.  State-of-the-art methods and tools have advanced our capabilities significantly facing the challenges comprehensive stability analysis tools  coordinated design of robust stability controls  on-line dynamic security assessment Industry yet to take full advantage of these developments!  Need to review and improve  The reliability criteria.
  28. 28. Thank You …..!