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Power System Technology Navigator (PSTN)                                                                                                                                              Saturday, November 19, 2011
Back to Overview                                                                                                                                                                                                  V. 1.1




                                                  F a c t o r s & P h e n o m e n a
                         - major benefits




                                                                                                 Reactive Power Factor
                           (link to PPT)
                         - major benefits




                                                                                                                                         Unbalanced load
                                                                     Interruptions
                           (link to Web)




                                                                                                                         Sags & Swells
                                                                                                                                                           Power System Technology Navigator
                         - additional




                                                         Harmonics




                                                                                     Loop flow
                           benefits                                                                                                                         Please select the slide show function


                                 DVR                                                                                                                                      for navigation
                            Energy Storage
                   m




                            Harmonic filters

                                HVDC
                   t e




                              HVDC Light
                   y s




                                Minicap

                         MINICOMP(STATCOM)
                   y S




                              PSGuard
                         Wide Area Monitoring
                    /




                          Series compensation                                                                                                                          Related Links:                  (online)
                   g




                            Shunt capacitor
                   l o




                                                                                                                                                                         Power T&D Solutions
                             Shunt reactor
                   o




                         Static Freq. Converter
                                                                                                                                                                         Power Generation Solutions
                   n




                                 SVC
                                                                                                                                                                         Motors, Drives & Power Electronics
                   h




                            SVC for Industry
                   c




                              STATCOM                                                                                                                                    High Voltage Products
                   e




                                 SVR
                                                                                                                                                                         Transformers
                   T




                                 TCSC
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Power System Technology Navigator (PSTN)                                                               Saturday, November 19, 2011
Back to Overview                                                                                                                V. 1.1



    Asynchronous connection
    The interconnected AC networks that tie the power
    generation plants to the consumers are in most cases
    large. The map below shows the European situation.


    There is one grid in Western Europe, one in Eastern
    Europe, one in the Nordic countries. Islands like Great
    Britain, Ireland, Iceland, Sardinia, Corsica, Crete,
    Gotland, etc. also have their own grid with no AC
    connection to the continent. The other continents on
    the globe have a similar situation.
    Even if the networks in Europe have the same nominal
    frequency, 50 cycles per second or Hertz (Hz), there is
    always some variation, normally less than ± 0.1 Hz,
    and in certain cases it may prove difficult or impossible
    to connect them with AC because of stability concerns.
    An AC tie between two asynchronous systems needs
    to be very strong to not get overloaded. If a stable AC
    tie would be too large for the economical power             European interconnected power grids.
    exchange needs or if the networks wish to retain their
    independence, than a HVDC link is the solution.
    And in other parts of the world (South America and
    Japan) 50 and 60 Hz networks are bordering each
    other and it would be impossible to exchange power
    between them with an AC line or cable. HVDC is then
    the only solution.


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Power System Technology Navigator (PSTN)                                 Saturday, November 19, 2011
Back to Overview                                                                                  V. 1.1

  Bottlenecks
  Constrained transmission paths or interfaces in an
  interconnected electrical system
  The term Bottlenecks is often interchangeable to
  congested transmission paths or interfaces. A
  transmission path or interface refers to a specific set of
  transmission elements between two neighboring
  control areas or utility systems in an interconnected
  electrical system. A transmission path or interface
  becomes congested when the allowed power transfer
  capability is reached under normal operating
  conditions or as a result of equipment failures and
  system disturbance conditions. The key impacts of
  Bottlenecks are reduction of system reliability,
  inefficient utilization of transmission capacity and
  generation resources, and restriction of healthy market
  competition.The ability of the transmission systems to
  deliver the energy is dependent on several main
  factors that are constraining the system, including
  thermal constraints, voltage constraints, and stability
  constraints. These transmission limitations are usually
  determined by performing detailed power flow and
  stability studies for a range of anticipated system
  operating conditions. Thermal limitations are the most
  common constraints, as warming and consequently
  sagging of the lines is caused by the current flowing in
  the wires of the lines and other equipment. In some
  situations, the effective transfer capability of
  transmission path or interface may have to be reduced
  from the calculated thermal limit to a level imposed by
                                                                         Back to Overview
  voltage constraints or stability constraints.
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Power System Technology Navigator (PSTN)                                 Saturday, November 19, 2011
Back to Overview                                                                                  V. 1.1



  Flicker
  A fluctuation in system voltage that can lead to
  noticeable changes in light output.
  Voltage Flicker can either be a periodic or aperiodic
  fluctuation in voltage magnitude i.e. the fluctuation may
  occur continuously at regular intervals or only on
  occasions. Voltage Flicker is normally a problem with
  human perception of lamp „strobing‟ effect but can also
  affect power-processing equipment such as UPS
  systems and power electronic devices.               Slowly
  fluctuating periodic flickers, in the 0.5 – 30.0Hz range,
  are considered to be noticeable by humans. A voltage
  magnitude variation of as little as 1.0% may also be
  noticeable.
  The main sources of flicker are industrial loads
  exhibiting continuous and rapid variations in the load
  current magnitude. This type of loads includes electric
  arc furnaces in the steel industry, welding machines,
  large induction motors, and wind power generators.
  High impedance in a power delivery system will
  contribute further to the voltage drop created by the
  line current variation.




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Power System Technology Navigator (PSTN)                               Saturday, November 19, 2011
Back to Overview                                                                                V. 1.1



  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
  non-sinusoidal and considered to be distorted.


  Nonlinear loads draw currents that are non-sinusoidal
  and thus create voltage drops in distribution conductors
  that are non-sinusoidal. Typical nonlinear loads include
  rectifiers, variable speed drives, and any other loads
  based on solid-state conversion. Transformers and
  reactors may also become nonlinear elements in a power
  system during overvoltage conditions. Harmonics create
  many concerns for utilities and customers alike. Typical
  phenomena include neutral circuit overloading in three
  phase circuits, motor and transformer overheating,
  metering inaccuracies and control system malfunctions.




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Power System Technology Navigator (PSTN)                                    Saturday, November 19, 2011
Back to Overview                                                                                     V. 1.1



  Interruptions
  Occur when the supply voltage drops below 10% of the
  nominal value
  An Interruption occurs whenever a supply‟s voltage drops
  below 10% of the rated voltage for a period of time no
  longer than one minute. It is differentiated from a voltage
  sag in that the late is not a severe power quality problem.
  The term sag covers voltage drops down to 10% of nominal
  voltage whereas an interruption occurs at lower than 10%.
  A Sustained Interruption occurs when this voltage decrease
  remains for more than one minute.
  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. Loss of stability
  is usually characterized by out-of-tolerance voltage
  magnitude conditions and frequency variations which
  exceed electrical machine and transformer tolerances. This
  phenomenon is often associated with faults and
  deficiencies in a transmission system but can also be the
  result of lack of generation resources. The concerns
  created by interruptions are evident and include
  inconvenience, loss of production time, loss of product, and
  loss of service to critical facilities such as hospitals.




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Power System Technology Navigator (PSTN)                                  Saturday, November 19, 2011
Back to Overview                                                                                   V. 1.1



  Long lines
  Long lines need special consideration in the planning of a
  power system.
  This transmission carries more than 12,000 MW over 800
  km. There is an HVDC system with two 600 kV bipoles of
  3150 MW each is direct route to São Paulo while the three
  800 kV shunt and series compensated AC lines has two
  intermediate substations that allow connection to the local
  grids.
  For long AC lines one must consider i.e. the reactive power
  compensation, the transient stability and switching
  overvoltages and how many intermediate substations one
                               needs.
  If the line length is longer than approx. 600 km one should
  also consider if an HVDC alternative brings lower
  investment costs and/or lower losses or if the inherent
  controllability of an HVDC system brings with some other
  benefits.
  Another factor to consider is the land use
  The figure at the right compares two 3,000 MW HVDC lines
  for the 1,000 km Three Gorges - Shanghai transmission,
  China, to five 500 kV AC lines that would have been used if
  AC transmission had been selected.
  Go to Long Cables



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Power System Technology Navigator (PSTN)                                                                Saturday, November 19, 2011
Back to Overview                                                                                                                  V. 1.1



  Long cables
  Cables have large capacitances and therefore, if fed with AC,
  large reactive currents. Cables for DC are also less expensive
  than for AC. One must distinguish between submarine cables
  and land (underground) cables.
  Submarine cables
  Since no shunt reactor can be installed at intermediate points
  (in the sea) and DC cables are less expensive, the majority of
  cables > 50 km are for DC.
  Underground cables
  Long underground cables (> 50 km) have been generally
  avoided since the cost for an overhead line was deemed to be
  only 10 – 20 % of the cost for the cable. In many parts of the       Laying of the 200 km Fenno-Skan HVDC cable (500 MW).
  world it is now almost impossible to get permission to build a
  new overhead line. HVDC Light ® has changed the cost relation
  and the cable solution is less expensive than before.




                                                                   Laying of the 180 km Murraylink HVDC Light cable (220 MW).

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Power System Technology Navigator (PSTN)                                                                            Saturday, November 19, 2011
Back to Overview                                                                                                                             V. 1.1



  Loop Flow
  Unscheduled power flow on a given transmission path in an
  interconnected electrical system
  The terms Loop Flow and Parallel Path Flow are sometimes
  used interchangeable to refer to the unscheduled power flows,
  that is, the difference between the scheduled and actual power
  flows, 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 neighboring
  control areas or utility systems.


  The reliability of an interconnected electrical system can be
                                                                              Transmission Loop Flows for 1000 KW scheduled Transfer from
  characterized by its capability to move electric power from one                     Area A to Area C in an Interconnected System
  area to another through all transmission circuits or paths
  between those areas under specified system conditions. The
  transfer capability may be affected by the “contract path”
  designated to wholesale power transactions, which assumes
  that the transacted power would be confined to flow along an
  artificially specified path through the involved transmission
  systems. In reality, the actual path taken by a transaction may
  be quite different from the designated routes, determined by
  physical laws not by commercial agreements, thus involving the
  use of transmission facilities outside the contracted systems.
  These unexpected flow patterns may cause so-called Loop
  Flow and Parallel Path Flow problems, which may limit the
  amount of power these other systems can transfer for their own
  purposes.
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Power System Technology Navigator (PSTN)                                          Saturday, November 19, 2011
Back to Overview                                                                                           V. 1.1



  Power Oscillations
  Periodic variations in generator angle or line angle due to
  transmission system disturbances
  Oscillations of generator angle or line angle are generally
  associated with transmission system disturbances and can
  occur due to step changes in load, sudden change of generator
  output, transmission line switching, and short circuits.
  Depending on the characteristics of the power system, the
  oscillations may last for 3 -20 seconds after a severe fault.
  Drawn out oscillations that last for a few seconds or more are
  usually the result of very light damping in the system and are
  pronounced at power transfers that approach the line‟s stability
  limit. During such angular oscillation period significant cycle
  variations in voltages, currents, transmission line flows will take
  place. It is important to damp these oscillations as quickly as
  possible because they cause mechanical wear in power plants
  and many power quality problems. The system is also more
  vulnerable if further disturbances occur.
  The active power oscillations on a transmission line tend to limit
  the amount of power that may be transferred, thus may result in
  stability concerns or utilization restrictions on the corridors
  between control areas or utility systems. This is due to the fact
  that higher power transfers can lead to less damping and thus
  more severe and possibly unstable oscillations.




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Power System Technology Navigator (PSTN)                                          Saturday, November 19, 2011
Back to Overview                                                                                           V. 1.1



  Reactive Power Factor
  Effects of reactive power on the efficiency of transmission and
  distribution
  Reactive power is defined as the product of the rms voltage,
  current, and the sine of the difference in phase angle between
  the two. It is used to describe the effects of a generator, a load,
  or other network equipment, which on the average neither
  supplies nor consumes power. Synchronous generators,
  overhead lines, underground cables, transformers, loads and
  compensating devices are the main sources and sinks of
  reactive power, which either produce or absorb reactive power
  in the systems. To maintain efficient transmission and
  distribution, it is necessary to improve the reactive power
  balance in a system by controlling the production, absorption,
  and flow of reactive power at all levels in the system. By
  contrast, inefficient reactive power management can result in
  high network losses, equipment overloading, unacceptable
  voltage levels, even voltage instability and outages resulting
  from voltage collapse. Local reactive power devices for voltage
  regulation and power factor correction are also important
  especially for balancing the reactive power demand of large and
  fluctuating industrial loads.




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Power System Technology Navigator (PSTN)                                            Saturday, November 19, 2011
Back to Overview                                                                                             V. 1.1



  Sags and Swells
  Short duration decrease/increase (sag/swell) in supply voltage
  A Voltage Sag or Voltage Dig is a decrease in supply voltage of
  10% to 90% that lasts in duration from half a cycle to one
  minute. A Voltage Swell is an increase in supply voltage of 10%
  to 80% for the same duration.
  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. Sags can be created by sudden but brief
  changes in load such as transformer and motor inrush and short
  circuit-type faults. A sag may also be created by a step change
  in load followed by a slow response of a voltage regulator. A
  voltage swell may occur by the reverse of the above events.
  Electronic equipment is usually the main victim of sags, as they
  do not contain sufficient internal energy to „ride through‟ the
  disturbance. Electric motors tend to suffer less from voltage
  sags, as motor and load inertias will „ride through‟ the sag if it is
  short enough in duration.




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Power System Technology Navigator (PSTN)                                         Saturday, November 19, 2011
Back to Overview                                                                                          V. 1.1



  Unbalanced Load
  A load which does not draw balanced current from a balanced
  three-phases supply
  An unbalanced load is a load which does not draw balanced
  current from a balanced three-phase supply.           Typical
  unbalanced loads are loads which are connected phase-to-
  neutral and also loads which are connected phase-to-phase.
  Such loads are not capable of drawing balanced three-phase
  currents. They are usually termed single-phase loads.
   A single-phase load, since it does not draw a balanced three-
  phase current, will create unequal voltage drops across the
  series impedances of the delivery system. This unequal voltage
  drop leads to unbalanced voltages at delivery points in the
  system. Blown fuses on balanced loads such as three-phase
  motors or capacitor banks will also create unbalanced voltage in
  the same fashion as the single-phase and phase-phase
  connected loads. Unbalanced voltage may also arise from
  impedance imbalances in the circuits that deliver electricity such
  as untransposed overhead transmission lines.                 Such
  imbalances give the appearance of an unbalanced load to
  generation units.
    An unbalanced supply may have a disturbing or even
  damaging effect on motors, generators, poly-phase converters,
  and other equipment. The foremost concern with unbalanced
  voltage is overheating in three-phase induction motors. The
  percent current imbalance drawn by a motor may be 6 to 10
  times the voltage imbalance, creating an increase in losses and
  in turn an increase in motor temperature. This condition may
  lead to motor failure.                                                         Back to Overview
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Power System Technology Navigator (PSTN)                                         Saturday, November 19, 2011
Back to Overview                                                                                          V. 1.1



  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. Lack of reactive power may
  essentially have two origins: firstly, a gradual increase of power
  demand without the reactive part being met in some buses or
  secondly, a sudden change in the network topology redirecting
  the power flows in such a way that the required reactive power
  cannot be delivered to some buses.
  The relation between the active power consumed in the
  considered area and the corresponding voltages is expressed in
  a static way by the P-V curves (also called “nose” curves). The
  increased values of loading are accompanied by a decrease in
  voltage (except in case of a capacitive load). When the loading
  is further increased, the maximum loadability point is reached,
  beyond which no additional power can be transmitted to the
  load under those conditions. In case of constant power loads
  the voltage in the node becomes uncontrollable and decreases
  rapidly. This may lead to the partial or complete collapse of a
  power system.




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Power System Technology Navigator (PSTN)                                                             Saturday, November 19, 2011
Back to Overview                                                                                                              V. 1.1

 Factors / Phenomena: Harmonics
 Technology / System: Harmonic Filters
 Example of application: Reducing harmonics in heavy industry
 Harmonic Filters may be used to mitigate, and in some cases, eliminate
 problems created by power system harmonics. Non-linear loads such as
 rectifiers, converters, home electronic appliances, and electric arc
 furnaces cause harmonics giving rise to extra losses in power equipment
 such as transformers, motors and capacitors. They can also cause other,
 probably more serious problems, when interfering with control systems
 and electronic devices. Installing filters near the harmonic sources can
 effectively reduce harmonics. For large, easily identifiable sources of
 harmonics, conventional filters designed to meet the demands of the
 actual application are the most cost efficient means of eliminating
 harmonics. These filters consist of capacitor banks with suitable tuning
 reactors and damping resistors. For small and medium size loads, active
 filters, based on power electronic converters with high switching
 frequency, may be a more attractive solution.
 Benefits:
 •Eliminates harmonics
 •Improved Power Factor
 •Reduced Transmission Losses
 •Increased Transmission Capability
 •Improved Voltage Control
 •Improved Power Quality
                                                                            more about Harmonic Filters and Harmonics
 Other applications:
 •Shunt Capacitors

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Power System Technology Navigator (PSTN)                                                                                 Saturday, November 19, 2011
Back to Overview                                                                                                                                   V. 1.1

 Factors / Phenomena: Reactive Power Factor
 Technology / System: Harmonic Filters
 Example of application: Regulation of the power factor to increase the
 transmission capability and reduce transmission losses as well as
 reducing harmonics.
 Harmonic Filters produced reactive power as well as mitigate, and in
 some cases, eliminate problems created by power system harmonics.
 Where the main need is power factor compensation the best solution can
 still be a harmonic filter due to the amount of harmonics. Non-linear loads
 such as rectifiers, converters, home electronic appliances, and electric arc
 furnaces cause harmonics giving rise to extra losses in power equipment
 such as transformers, motors and capacitors. They can also cause other,
 probably more serious problems, when interfering with control systems
 and electronic devices. Installing filters near the harmonic sources can
 effectively reduce harmonics. For large, easily identifiable sources of
 harmonics, conventional filters designed to meet the demands of the
 actual application are the most cost efficient means of eliminating
 harmonics as well as producing reactive power. These filters consist of
 capacitor banks with suitable tuning reactors and damping resistors. For
 small and medium size loads, active filters, based on power electronic
 converters with high switching frequency, may be a more attractive
 solution.
 Benefits:
 Improved power factor, Reduced transmission losses, Increased transmission capability
 Improved voltage control, Improved power quality, Eliminates harmonics
                                                                                         more about Harmonic Filters and Reactive Power Factor
 Other applications:
 Shunt capacitors

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Power System Technology Navigator (PSTN)                                                                            Saturday, November 19, 2011
Back to Overview                                                                                                                               V. 1.1

 Factors / Phenomena: Asynchronous connection
 Technology / System: HVDC and HVDC Light®
 Example of application: Interconnection of power systems
 It is sometimes difficult or impossible to connect two AC networks due to
 stability reasons. In such cases HVDC is the only way to make an
 exchange of power between the two networks possible.
 Several HVDC links interconnect AC system that are not running in
 synchronism with each other. For example the Nordel power system in
 Scandinavia is not synchronous with the UCTE grid in western continental
 Europe even though the nominal frequencies are the same. And the
 power system of eastern USA is not synchronous with that of western
 USA. There are also HVDC links between networks with different nominal
 frequencies (50 and 60 Hz) in Japan and South America.
 Direct current transmissions in the form of classical HVDC or HVDC                 The Scandinavia - Northern Europe HVDC interconnections
 Light® are the only efficient means of controlling power flow in a network.
 HVDC can therefore never become overloaded. An AC network connected
 with neighboring grids through HVDC links may as the worst case loose          Links:
 the power transmitted over the link, if the neighboring grid goes down - the
                                                                                •HVDC transmission for controllability of power flow
 HVDC transmission will act as a firewall against cascading disturbances.
                                                                                •HVDC transmission for asynchronous connection
 Benefits:
                                                                                •Applications in Power Systems: Interconnection
 •The networks can retain their independence                                    •ABB HVDC Portal
 •An HVDC link can never be overloaded
 •HVDC transmission will act as a firewall against cascading disturbances.
                                                                                    more about HVDC & Asynchronous Connection




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Power System Technology Navigator (PSTN)                                                                      Saturday, November 19, 2011
Back to Overview                                                                                                                        V. 1.1

 Factors / Phenomena: Bottlenecks
 Technology / System: HVDC and HVDC Light®
 Example of application: Interconnection of power systems
 Bottlenecks may be relieved by the use of an HVDC or HVDC Light link in
 parallel with the limiting section of the grid. By using the inherent
 controllability of the HVDC system the power system operator can decide
 how much power that is transmitted in the AC-link and how much by the
 HVDC system.
 Longer AC lines tend to have stability constrained capacity limitations as
 opposed to the higher thermal constraints of shorter lines. By using the
 inherent controllability of an HVDC system in parallel with the long AC
 lines, the power system can be stabilized and the transmission limitations
 on the AC line can be increased.


 Benefits:
 •Increased Power Transfer Capability                                         Links:
 •Additional flexibility in Grid Operation                                    •HVDC transmission for controllability of power flow

 •Improved Power and Grid Voltage Control                                     •Applications in Power Systems: Interconnection
                                                                              •ABB HVDC Portal
 •An HVDC link can never be overloaded!


 .
                                                                                  more about HVDC & Bottlenecks




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Power System Technology Navigator (PSTN)                                                                    Saturday, November 19, 2011
Back to Overview                                                                                                                     V. 1.1

 Phenomena / Factor: Long lines
 Technology / System: HVDC
 Example of application: Expressway for power
 A HVDC transmission line costs less than an AC line for the same
 transmission capacity. However, the terminal stations are more expensive
 in the HVDC case due to the fact that they must perform the conversion
 from AC to DC and vice versa. But above a certain distance, the so-called
 "break-even distance", the HVDC alternative will always give the lowest
 cost. Therefore many long overhead lines (> 700 km) particularly from
 remote generating stations are built as DC lines.
 Benefits:
 •Lower investment cost
 •Lower losses
 •Lower right-of-way requirement for DC lines than for AC lines              Links:
 •HVDC does not contribute to the short circuit current                      •HVDC transmission for lower investment cost
                                                                             •HVDC transmission has lower losses
                                                                             •Applications in Power Systems: Connection of
 => Go to Long Submarine Cables
                                                                             generation
                                                                             •ABB HVDC Portal




 .                                                                            more about HVDC & Long Lines




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Power System Technology Navigator (PSTN)                                                              Saturday, November 19, 2011
Back to Overview                                                                                                                V. 1.1

 Phenomena / Factor: Long submarine cables
 Technology / System: HVDC
 Example of application: long distance water crossing
 In a long AC cable transmission, the reactive power flow due to the large
 cable capacitance will limit the maximum possible transmission distance.
 With HVDC there is no such limitation, why, for long cable links, HVDC is
 the only viable technical alternative. There are HVDC and HVDC Light
 cables from 40 km up to 580 km in operation or under construction with
 power ratings from 40 to 700 MW.


 Benefits:
 •Lower investment cost
 •Lower losses
                                                                             Links:
                                                                             •HVDC submarine cables
                                                                             •ABB HVDC Portal




 .



                                                                              more about HVDC & Long Submarine Cables




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Power System Technology Navigator (PSTN)                                                                       Saturday, November 19, 2011
Back to Overview                                                                                                                           V. 1.1

 Factors / Phenomena: Loop Flow
 Technology / System: HVDC and HVDC Light
 Example of application: Interconnected power systems
 Loop Flows, or Parallel Path Flows, may be alleviated by the use of HVDC
 or HVDC Light. In interconnected power systems, the actual path taken by
 a transaction from one area to another may be quite different from the
 designated routes as the result of parallel path admittance, thus diverting
 or wheeling power over parallel connections.
 The figure shows how parallel path flow can be avoided by replacing an
 AC line with a HVDC/HVDC Light link between area A and area C
 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       Links:
 losses
                                                                               HVDC transmission for controllability of power flow
 •An HVDC link can never be overloaded!                                        ·    Applications in Power Systems: Interconnection
                                                                               ABB HVDC Portal




                                                                                   more about HVDC & Loop Flow


 .
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Power System Technology Navigator (PSTN)                                                                     Saturday, November 19, 2011
Back to Overview                                                                                                                      V. 1.1

 Factors / Phenomena: Power Oscillations
 Technology / System: HVDC and HVDC Light®
 Example of application: Steady State and Transient Stability
 Improvement
 Long AC lines tend to have stability constrained capacity limitations as
 opposed to the higher thermal constraints of shorter lines. By using the
 inherent controllability of an HVDC system in parallel with the long AC
 lines, the power system can be stabilized and the transmission limitations
 on the AC line can be increased.
 The HVDC damping controller is a standard feature in many HVDC
 projects in operation. It normally takes its input from the phase angle
 difference in the two converter stations.



                                                                              Links:
 Benefits:
                                                                              HVDC transmission for controllability of power flow
 •Increased Power Transfer Capability                                         Applications in Power Systems: Interconnection
 •Improved Power and Grid Voltage Control                                     HVDC Light System Interaction Tutorial.

 •An HVDC link can never be overloaded!                                       ABB HVDC Portal




                                                                                more about HVDC & Power Oscillations




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Power System Technology Navigator (PSTN)                                                   Saturday, November 19, 2011
Back to Overview                                                                                                     V. 1.1

 Factors / Phenomena: Flicker
 Technology / System: MiniCap
 Example of application: Installation of a MiniCap to reduce flicker
 during large motor starting
 Voltage flicker can become a significant problem for power distributors
 when large motor loads are introduced in remote locations. Installation of
 a series capacitor in the feeder strengthens the network and allows such
 load to be connected to existing lines, avoiding more significant
 investment in new substations or new distribution lines.
 The use of the MiniCap on long distribution feeders provides self-
 regulated reactive power compensation that efficiently reduces voltage
 variations during large motor starting.




 Benefits:
 •Reduced voltage fluctuations (flicker)
 •Improved voltage profile along the line
 •Easier starting of large motors
 •Self-regulation
                                                                              more about MiniCap and Flicker




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Power System Technology Navigator (PSTN)                                                                 Saturday, November 19, 2011
Back to Overview                                                                                                                  V. 1.1

 Factors / Phenomena: Long lines & cables
 Technology / System: MiniCap
 Example of application: Improved voltage profile of long distribution
 lines by adding a MiniCap
 The voltage profile on a radial circuit depends on the circuit parameters
 and the load characteristics. The voltage profile can be significantly
 improved by installing a MiniCap along the line. A typical voltage profile
 for a radial circuit with and without a series capacitor is shown below.
 Note that the voltage profile curve has a jump at the location of the series
 capacitor which represents a large voltage rise downstream of the series
 capacitor.
 The use of the MiniCap on long distribution feeders provides improved
 voltage profile for all loads downstream of the installation.




 Benefits:
 •Increased power transmission capability through decreased total line
 reactance
 •Improved voltage profile along the line
 •Reduced line losses

                                                                                more about MiniCap and Long lines & cables




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Power System Technology Navigator (PSTN)                                                                   Saturday, November 19, 2011
Back to Overview                                                                                                                    V. 1.1

 Factors / Phenomena: Reactive Power Factor
 Technology / System: MiniCap
 Example of application: Improved power factor at the utility source
 with a MiniCap
 The reactive power produced by the series capacitor is proportional to the
 capacitor impedance and the line current. With the series capacitor
 supplying a significant portion of the reactive power requirements of the
 distribution line and of inductive motor loads, much less reactive power is
 drawn from the utility source, resulting in a greatly improved power factor
 at the sending end of the line.
 The use of the MiniCap on a distribution feeder provides self-regulated
 reactive power for improved power factor at the utility source.




 Benefits:
 •Increased power factor at the utility source
 •Easier starting of large motors
 •Improved voltage regulation and reactive power balance
 •Self-regulation



                                                                               more about MiniCap and Reactive Power Factor




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Power System Technology Navigator (PSTN)                                                                        Saturday, November 19, 2011
Back to Overview                                                                                                                          V. 1.1

 Factors / Phenomena: Bottlenecks
 Technology / System: PSGuard Wide Area Monitoring System
 Example of application: Phase angle monitoring
 The phase angle monitoring application facilitates the monitoring of
 network stresses caused by heavily loaded lines. It provides operators
 with real-time information about voltage phase angle deviations – a crucial
 issue e.g. for the successful reclosing of transmission lines.
 Its main function is to supply sufficient information to the power system
 operator to evaluate the present angle difference between two locations.
 Upon detection of an extraordinary status, PSGuard alerts the operator by           PSGuard display: Phase angle monitoring with
 giving an early warning or, in critical cases, an emergency alarm.                     early warning and emergency alarm

 The present version provides monitoring functionality, and its outputs are
 intended as mature decision support for operators in taking stabilizing
 measures. Actions that the operator may take to improve grid stability
 range from generation rescheduling or actions on the reactive power
 compensation, blocking of tap changers in the load area and load
 shedding in extreme cases.
 Benefits:
 •Improved system stability, security and reliability
 •Safe operation of power carrying components closer to their limits
 •Optimized utilization of transmission capacities
 •Enhanced operational and planning safety
                                                                               more about: PSGuard Wide Area Monitoring System
 Other applications:
                                                                               and Bottlenecks
 •Line Thermal Monitoring (LTM)
 •Voltage Stability Monitoring (VSM)
 •Power Oscillation Monitoring (POM)                                                                             Back to Overview
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Power System Technology Navigator (PSTN)                                                                                                Saturday, November 19, 2011
Back to Overview                                                                                                                                                    V. 1.1

 Factors / Phenomena: Long lines and cables
 Technology / System: PSGuard Wide Area Monitoring System
 Example of application: Line thermal monitoring
 Loading of power lines or HV cables is in many cases constrained by thermal limits
 rather than by voltage instability concerns. A thermal limit of a line is usually set
 according to conservative and stabile criteria, i.e. high ambient temperature and calm
 air. This yields assumptions of very limited cooling possibilities and thus low loadability.
 However, the ambient conditions are often much better in terms of possible cooling and
 would allow higher loading of a line with a minimal risk. This can be achieved if an on-
 line tool for line temperature assessment is available. One of the algorithms of PSGuard
 serves this purpose. However, its functionality and applicability on the real power
 systems should be tested in the practice.
                                                                                                        PSGuard display: Line thermal monitoring with early
 The algorithm works as follows                                                                                  warning and emergency alarm
 •The voltage and current phasors measured at both ends of a line are collected (the
 phasors have to be measured at the same instant, which is possible through the GPS-
 synchronization of the phasor measurement units, PMUs)
 •Actual impedance and shunt admittance of a line are computed.
 •Resistance of the line/cable is extracted
 •Based on the known properties of the conductor material (reference temperature and
 dependency coefficient are usually supplied by the manufacturer), the actual average
 temperature of the line is determined.
 The obtained temperature is an average, not the spot one. The relation between them
 shall be verified, i.e. through consideration of the impact of the various weather
                                                                                                   PSGuard display: Line temperature pattern computed by PSGuard
 conditions along the line at a given time.
 Benefits:
 •Improved power flow control                                                                   more about: PSGuard Wide Area Monitoring System
 •Safe operation of power carrying components closer to their limits                            and Long Lines & Cables
 Other applications:
 •Power Oscillation Monitoring (POM)
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Power System Technology Navigator (PSTN)                                                                                          Saturday, November 19, 2011
Back to Overview                                                                                                                                                 V. 1.1

 Factors / Phenomena: Oscillations
 Technology / System: PSGuard Wide Area Monitoring System
 Example of application: Power oscillation monitoring
 Power oscillation monitoring is the algorithm used for the detection of
 power swings in a high voltage power system. The algorithm processes the
 selected voltage and current phasor inputs and detects the various power
 swing (power oscillation) modes. It quickly identifies the frequency and the
 damping of swing modes. The algorithm deploys adaptive Kalman filtering
 techniques.
 Displayed results
                                                                                               Measurements by PSGuard WAMS: The loss of a power
 •Damping of the dominant oscillatory mode (time window, i.e. trend display)                   plant in Spain (1000 MW) initiated Wide Area Oscillations
                                                                                                               Measurement by PSGuard
 •Frequency of the dominant oscillatory mode (time window, i.e. trend display)

 •Amplitude of the oscillation (time window, i.e. trend display)

 Optional
 •Damping of other oscillatory modes (all in one time window, distinguished by different
 colors)
 •Frequencies of other oscillatory modes (all in one time window, distinguished by different
 colours
 Alarms
 When the damping of any oscillation mode decreases to below a predefined value (in two
 steps, first is alert, the second emergency alarm)

 Read more




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Power System Technology Navigator (PSTN)                                                                                                 Saturday, November 19, 2011
Back to Overview                                                                                                                                                      V. 1.1

 Factors / Phenomena: Oscillations
 Technology / System: PSGuard Wide Area Monitoring System
 Example of application: Power oscillation monitoring




 Benefits:
 •Increased power transfer
 •Enhanced security

 Short-term operation benefits:                                                                         Example: Estimation of relative frequency and damping
 •Immediate awareness of the power system state in terms of the presence of oscillations,
 thus an operator sees the urgency of the situation
 •Indication of the frequency of an oscillation which may then be associated with the known
 existing mode of the power system, i.e. the operator may distinguish if a local or inter-area
 mode is excited

 Long-term benefits:
 •With the help of the stored data, long-term statistics can be collected and, based on their
 evaluation, the system reinforcements can be performed (such as retuning of Power
 System Stabilizers (PSS) to damp the frequencies appearing most often as dangerous
 ones).




                                                                                                 more about: PSGuard Wide Area Monitoring System
                                                                                                 and Power Oscillations



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Power System Technology Navigator (PSTN)                                                                                    Saturday, November 19, 2011
Back to Overview                                                                                                                                        V. 1.1

 Factors / Phenomena: Voltage instability
 Technology / System: PSGuard Wide Area Monitoring System
 Example of application: Voltage stability monitoring
 The voltage stability monitoring application facilitates the monitoring of the
 grid‟s dynamic behavior and provides stability calculations for steady state
 situations as well as stability predictions in contingency cases. It builds on
 and extends the basic functionality of PSG830 with functions related to the
 monitoring of voltage stability for a transmission line / corridor.
 It‟s main function is to provide the operator of the power system with
 sufficient information to evaluate the present power margin with respect to
 voltage stability, that is, the amount of additional active power that can be          PSGuard display: Voltage stability monitoring P-V Curve

 transported on a transmission corridor without jeopardizing the voltage
 stability. The present version provides monitoring functionality, and its
 outputs are intended as mature decision support for operators in taking
 optimizing resp. stabilizing measures. Actions that the operator may take to
 improve voltage stability range from generation rescheduling or actions on
 the reactive compensation, blocking of tap changers in the load area and to
 load shedding in extreme cases.
 Applied directly, the application is assigned to a single line or cable.
 However, on a case-by-case basis, the method can be applied also to
 transmission corridors with more complex topologies.
 Benefits:
 •Improved system stability, security and reliability
                                                                                  more about: PSGuard Wide Area Monitoring System
 •Reduced cost and greater functionality of Protection & Control systems          and Voltage Instability
 •Safe operation of power carrying components closer to their limits
 •Optimized utilization of transmission capacities
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Power System Technology Navigator (PSTN)                                                                      Saturday, November 19, 2011
Back to Overview                                                                                                                       V. 1.1

 Factors / Phenomena: Bottlenecks
 Technology / System: Series Compensation
 Example of application: Transient Stability Improvement
 Bottlenecks may be relieved by the use of Series Compensation. Longer
 lines tend to have stability-constrained capacity limitations as opposed to
 the higher thermal constraints of shorter lines. Series Compensation has
 the net effect of reducing transmission line series reactance, thus
 effectively reducing the line length. Series Compensation also offers
 additional power transfer capability for some thermal-constrained
 bottlenecks by balancing the loads among the parallel lines. Figure shows
 a two-area interconnected system where the power transfer from area A to
 area B is limited to 1500MW due to stability constraints. Additional
 electricity can be delivered from area A to area B if Series Compensation is
 applied to increase the maximum stability limits.
 Benefits:
 •Increased Power Transfer Capability
 •Additional flexibility in Grid Operation
 •Improved Grid Voltage Control
 Other applications:
 •Power Flow Control



                                                                                more about Series Compensation and Bottlenecks



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Power System Technology Navigator (PSTN)                                                                       Saturday, November 19, 2011
Back to Overview                                                                                                                        V. 1.1

 Factors / Phenomena: Loop Flows
 Technology / System: Series Compensation
 Example of application: Power Flow Control
 Loop Flows, or Parallel Path Flows, may be alleviated by the use of Series
 Compensation. In interconnected power systems, the actual path taken by
 a transaction from one area to another may be quite different from the
 designated routes as the result of parallel path admittance, thus diverting or
 wheeling power over parallel connections.
 Figure shows parallel path flow alleviation by the use of Series
 Compensation. With a reduction in the direct interconnection impedance
 between area A and area C, the Parallel Path Flow which is routed through
 area B is decreased.
 Benefits:
 •Increased Power Transfer Capability
 •Additional flexibility in Grid Operation
 •Lower Transmission Losses
 •Improved Transient Stability
 •Improved Grid Voltage Control
 Other applications:
 •Transient Stability Improvement
                                                                                  more about Series Compensation and Loop Flows




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Power System Technology Navigator (PSTN)                                                                      Saturday, November 19, 2011
Back to Overview                                                                                                                       V. 1.1

 Factors / Phenomena: Reactive Power Factor
 Technology / System: Shunt Capacitor
 Example of application:
 Regulation of the power factor to increase the transmission capability and
 reduce transmission losses
 Shunt capacitors are primarily used to improve the power factor in
 transmission and distribution networks, resulting in improved voltage
 regulation, reduced network losses, and efficient capacity utilization. Figure
 shows a plot of terminal voltage versus line loading for a system that has a
 shunt capacitor installed at the load bus. Improved transmission voltage
 regulation can be obtained during heave power transfer conditions when
 the system consumes a large amount of reactive power that must be
 replaced by compensation. At the line surge impedance loading level, the
 shunt capacitor would decrease the line losses by more than 35%. In
 distribution and industrial systems, it is common to use shunt capacitors to
 compensate for the highly inductive loads, thus achieving reduced delivery
 system losses and network voltage drop.
 Benefits:
 •Improved power factor
 •Reduced transmission losses
 •Increased transmission capability
 •Improved voltage control
                                                                                  more about Shunt Capacitor and Reactive Power
 •Improved power quality                                                          Factor

 Other applications:
 •Harmonic Filters
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Power System Technology Navigator (PSTN)                                                             Saturday, November 19, 2011
Back to Overview                                                                                                              V. 1.1

 Factors / Phenomena: Voltage instability
 Technology / System: Shunt Reactor
 Example of application: Extra/Ultra High Voltage air insulated
 transmission line and cable line voltage stability
 The primary purpose of the shunt reactor is to compensate for capacitive
 charging voltage, a phenomenon getting more prominent for increasing line
 voltage. Long high-voltage transmission lines and relatively short cable
 lines (since a power cable has high capacitance to earth) generate a large
 amount of reactive power during light power transfer conditions which must
 be absorbed by compensation. Otherwise, the receiving terminals of the
 transmission lines will exhibit a “voltage rise” characteristic and many types
 of power equipment cannot withstand such overvoltages. Figure shows at
 top level voltage at the receiving end when transmission line is loaded with
 rated power. Then shunt reactor is not needed. Next figure shows a voltage
 increase when line is lightly loaded and bottom figure shows what happens
 when a shunt reactor is connected. The voltage stability is kept due to the
 inductive compensation from the reactor.
 A better fine tuning of the reactive power can be made by the use of a tap
 changer in the shunt reactor. It can be possible to vary the reactive power
 between 50 to 100 % of the needed power.
 Benefits:
 •Simple and robust customer solution with low installation costs and
 minimum maintenance
 •No losses from an intermediate transformer when feeding reactive more about Shunt Capacitor and Voltage Instability
 compensation from a lower voltage level.
 •No harmonics created which may require filter banks.
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Power System Technology Navigator (PSTN)                                                                    Saturday, November 19, 2011
Back to Overview                                                                                                                      V. 1.1

 Factors / Phenomena: Bottlenecks
 Technology / System: Static Var Compensator (SVC)
 Example of application: Grid Voltage Support
 Static Var Compensators are used in transmission and distribution
 networks mainly providing dynamic voltage support in response to system
 disturbances and balancing the reactive power demand of large and
 fluctuating industrial loads. A Static Var Compensator is capable of both
 generating and absorbing variable reactive power continuously as opposed
 to discrete values of fixed and switched shunt capacitors or reactors.
 Further improved system steady state performance can be obtained from
 SVC applications. With continuously variable reactive power supply, the
 voltage at the SVC bus may be maintained smoothly over a wide range of
 active power transfers or system loading conditions. This entails the
 reduction of network losses and provision of adequate power quality to the
 electric energy end-users.
 Benefits:
 •Increased Power Transfer Capability
 •Additional flexibility in Grid Operation
 •Improved Grid Voltage Stability
 •Improved Grid Voltage Control
 •Improved Power Factor
 Other applications:                                                          more about Static Var Compensator and Bottlenecks

 •Power Oscillation Damping
 •Power Quality (Flicker Mitigation, Voltage Balancing)
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Power System Technology Navigator (PSTN)                                                                      Saturday, November 19, 2011
Back to Overview                                                                                                                        V. 1.1

 Factors / Phenomena: Power Oscillations
 Technology / System: Static Var Compensator (SVC)
 Example of application: Power Oscillation Damping
 Static Var Compensators are mainly used to perform voltage and reactive
 power regulation. However, when properly placed and controlled, SVCs
 can also effectively counteract system oscillations. A SVC, in effect, has
 the ability to increase the damping factor (typically by 1-2 MW per Mvar
 installed) on a bulk power system which is experiencing power oscillations.
 It does so by effectively modulating its reactive power output such that the
 regulated SVC bus voltage would increase the system damping capability.
 Figure shows power oscillation prompted by a disturbance on a
 transmission system. The uncompensated system undergoes substantial
 oscillations following the disturbance while the same system with SVC
 experiences much improved response.
 Benefits:
 •Increased Power Transfer Capability
 •Additional flexibility in Grid Operation
 •Improved Dynamic Stability
 Other applications:
 •Power Quality (Flicker Mitigation, Voltage Balancing)
 •Grid Voltage Support
                                                                                more about Static Var Compensator and
                                                                                Power Oscillations



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Power System Technology Navigator (PSTN)                                                                    Saturday, November 19, 2011
Back to Overview                                                                                                                      V. 1.1

 Factors / Phenomena: Voltage instability
 Technology / System: Static Var Compensator (SVC)
 Example of application: Grid Voltage Support
 Static Var Compensators are used in transmission and distribution
 networks mainly providing dynamic voltage support in response to system
 disturbances and balancing the reactive power demand of large and
 fluctuating industrial loads. A Static Var Compensator is capable of both
 generating and absorbing variable reactive power continuously as opposed
 to discrete values of fixed and switched shunt capacitors or reactors.
 Further improved system steady state performance can be obtained from
 SVC applications. With continuously variable reactive power supply, the
 voltage at the SVC bus may be maintained smoothly over a wide range of
 active power transfers or system loading conditions. This entails the
 reduction of network losses and provision of adequate power quality to the
 electric energy end-users.
 Benefits:
 •Increased Power Transfer Capability
 •Additional flexibility in Grid Operation
 •Improved Grid Voltage Stability
 •Improved Grid Voltage Control
 •Improved Power Factor
 Other applications:                                                          more about Static Var Compensator and

 •Power Oscillation Damping                                                   Voltage Instability

 •Power Quality (Flicker Mitigation, Voltage Balancing)
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Power System Technology Navigator (PSTN)                                                                     Saturday, November 19, 2011
Back to Overview                                                                                                                       V. 1.1

 Factors / Phenomena: Flicker
 Technology / System: SVC (Industry)
 Example of        application:   Power    Quality   Improvement,   Flicker
 Mitigation
 SVC is used most frequently for compensation of disturbances generated
 by the Electrical Arc Furnaces (EAF). With a well-designed SVC,
 disturbances such as flicker from the EAF are mitigated. Figure shows the
 flicker mitigation effect of a SVC installed at a steel making plant.
 Flicker, the random variation in light intensity from incandescent lamps
 caused by the operating of nearby fluctuating loads on the common electric
 supply grid, is highly irritating for those affected. The random voltage
 variations can also be disturbing to other process equipment fed from the
 same grid. The proper mitigation of flicker is therefore a matter of power
 quality improvement as well as an improvement to human environment.
 Benefits:
 •Reduced Flicker
 •Harmonic Filtering
 •Voltage Balancing
 •Power Factor Correction
 •Furnace/mill Process Productivity Improvement
 Other applications:
                                                                              more about SVC (Industry) and Flicker
 •General Reactive Power Compensation at Steelworks
 •Grid Voltage Support

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Power System Technology Navigator (PSTN)                                                                         Saturday, November 19, 2011
Back to Overview                                                                                                                          V. 1.1

 Factors / Phenomena: Reactive Power Factor
 Technology / System: SVC (Industry)
 Example of application: Reactive Power Compensation at Steelworks
 Static Var Compensators provide dynamic voltage support to balance the
 reactive power demand of large and fluctuating industrial loads. A Static
 Var Compensator is capable of both generating and absorbing variable
 reactive power continuously as opposed to discrete values of fixed and
 switched shunt capacitors or reactors. With continuously variable reactive
 power supply, the voltage at the SVC bus may be maintained smoothly
 over a wide range of operating conditions. This entails the improved power
 factor and sufficient power quality, leading to better process and production
 economy.
 Benefits:
 •Power Factor Correction
 •Furnace/mill Process Productivity Improvement
 •Harmonic Filtering
 Other applications:
 •Power Quality Improvement, Flicker mitigation
 •Power Quality Improvement, Voltage Balancing


                                                                                 more about SVC (Industry) and
                                                                                 Reactive Power Factor



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Power System Technology Navigator (PSTN)                                                                        Saturday, November 19, 2011
Back to Overview                                                                                                                         V. 1.1

 Factors / Phenomena: Unbalanced Load
 Technology / System: SVC (Industry)
 Example of application: Railway Feeder connected to the Public Grid
 The traction system is a major source of unbalanced loads. Electrification
 of railways, as an economically attractive and environmentally friendly
 investment in infrastructure, has introduced an unbalanced and heavy
 distorted load on the three-phase transmission grid. Without compensation,
 this would result in significant unbalanced voltage affecting most
 neighboring utility customers.      The SVC can elegantly be used to
 counteract the unbalances and mitigate the harmonics such that the power
 quality within the transmission grid is not impaired. Figure shows a typical
 traction substation arrangement with a load balancer (an asymmetrically
 controlled SVC). The load balancer transfers active power between the
 phases such that the balanced voltage can be created (seen from the grid).
 Benefits:
 •Voltage Balancing
 •Harmonic Filtering
 •Power Factor Correction
 Other applications:
 •Power Quality Improvement, Flicker Mitigation
 •Grid Voltage Support
                                                                                more about SVC (Industry) and
                                                                                Unbalanced Load



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Power System Technology Navigator (PSTN)                                                                    Saturday, November 19, 2011
Back to Overview                                                                                                                     V. 1.1

 Factors / Phenomena: Bottlenecks
 Technology / System: STATCOM®
 Example of application: Grid Voltage Support
 STATCOM, when connected to the grid, can provide dynamic voltage
 support in response to system disturbances and balance the reactive
 power demand of large and fluctuating industrial loads. A STATCOM is
 capable of both generating and absorbing variable reactive power
 continuously as opposed to discrete values of fixed and switched shunt
 capacitors or reactors. With continuously variable reactive power supply,
 the voltage at the STATCOM bus may be maintained smoothly over a wide
 range of system operation conditions. This entails the reduction of network
 losses and provision of sufficient power quality to the electric energy end-
 users.
 Benefits:
 •Increased Power Transfer Capability
 •Additional flexibility in Grid Operation
 •Improved Grid Voltage Stability
 •Improved Grid Voltage Control
 •Improved Power Factor
 Other applications:
 •Power Quality (Flicker Mitigation, Voltage Balancing)
                                                                                more about STATCOM and Bottlenecks




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Power System Technology Navigator (PSTN)                                                                      Saturday, November 19, 2011
Back to Overview                                                                                                                       V. 1.1

 Factors / Phenomena: Flicker
 Technology / System: STATCOM®
 Example of        application:    Power   Quality    Improvement,      flicker
 mitigation
 STATCOM® is an effective method used to attack the problem of flicker.
 The unbalanced, erratic nature of an electric arc furnace (EAF) causes
 significant fluctuating reactive power demand, which ultimately results in
 irritating electric lamp flicker to neighboring utility customers. In order to
 stabilize voltage and reduce disturbing flicker successfully, it is necessary
 to continuously measure and compensate rapid changes by means of
 extremely fast reactive power compensation. STATCOM® uses voltage
 source converters to improve furnace productivity similar to a traditional
 SVC while offering superior voltage flicker mitigation due to fast response
 time. Figure shows the flicker mitigation effect of an STATCOM® installed at
 a steel making plant.
 Benefits:
 •Eliminated Flicker
 •Harmonic Filtering
 •Voltage Balancing
 •Power Factor Correction
 •Furnace/mill Process Productivity Improvement
 Other applications:                                                              more about STATCOM and Flicker

 •Grid Voltage Support
 •Power Quality Improvement
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Power System Technology Navigator (PSTN)                                                                Saturday, November 19, 2011
Back to Overview                                                                                                                 V. 1.1

 Factors / Phenomena: Unbalanced Load
 Technology / System: STATCOM®
 Example of application: Railway Feeder connected to the Public Grid
 Modern electric rail system is a major source of unbalanced loads.
 Electrification of railways, as an economically attractive and
 environmentally friendly investment in infrastructure, has introduced an
 unbalanced and heavy distorted load on the three-phase transmission grid.
 Without compensation, this would result in significant unbalanced voltage
 affecting most neighboring utility customers.       Similar to SVC, the
 STATCOM can elegantly be used to restore voltage and current balance in
 the grid, and to mitigate voltage fluctuations generated by the traction
 loads. Figure shows a conceptual diagram of STATCOM application for
 dynamic load balancing for traction.
 Benefits:
 •Voltage Balancing
 •Harmonic Filtering
 •Power Factor Correction
 Other applications:
 •Power Quality Improvement, Flicker Mitigation
 •Grid Voltage Support

                                                                             more about STATCOM and Unbalanced Load




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Power System Technology Navigator (PSTN)                                                                      Saturday, November 19, 2011
Back to Overview                                                                                                                       V. 1.1

 Factors / Phenomena: Voltage instability
 Technology / System: STATCOM®
 Example of application: Grid Voltage Support
 STATCOM, when connected to the grid, can provide dynamic voltage
 support in response to system disturbances and balance the reactive
 power demand of large and fluctuating industrial loads. A STATCOM is
 capable of both generating and absorbing variable reactive power
 continuously as opposed to discrete values of fixed and switched shunt
 capacitors or reactors. With continuously variable reactive power supply,
 the voltage at the STATCOM bus may be maintained smoothly over a wide
 range of system operation conditions. This entails the reduction of network
 losses and provision of sufficient power quality to the electric energy end-
 users.
 Benefits:
 •Increased Power Transfer Capability
 •Additional flexibility in Grid Operation
 •Improved Grid Voltage Stability
 •Improved Grid Voltage Control
 •Improved Power Factor
 Other applications:
 •Power Quality (Flicker Mitigation, Voltage Balancing)
                                                                                more about STATCOM and Voltage Instability




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Power System Technology Navigator (PSTN)                                                                     Saturday, November 19, 2011
Back to Overview                                                                                                                       V. 1.1

 Factors / Phenomena: Bottlenecks
 Technology / System: TCSC
 Example of application: Transient Stability Improvement
 Bottlenecks may be effectively relieved by the use of entirely or partially
 thyristor controlled series compensation. As with conventional SC
 technology, TCSC can improve stability of power transmission, reactive
 power balance, and load sharing between parallel lines, thus mitigating the
 impact of transmission bottlenecks. Figure shows a two-area
 interconnected system where the power transfer from area A to area B is
 limited to 1500MW due to stability constraints. Additional electricity can be
 delivered from area A to area B if series compensation is applied to
 increase the maximum stability limits. High degree of series compensation
 level is permitted with the controlled series compensation achieving further
 improved transmission capacity utilization.
 Benefits:
 •Increased Power Transfer Capability
 •Additional flexibility in Grid Operation
 •Improve Dynamic Stability
 •Improved Grid Voltage Control
 •Immunity against Subsynchronous Resonance
 Other applications:
                                                                                 more about TCSC and Bottlenecks
 •Power Oscillation Damping
 •Subsynchronous Resonance Mitigation


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Power System Technology Navigator (PSTN)                                                                   Saturday, November 19, 2011
Back to Overview                                                                                                                    V. 1.1

 Factors / Phenomena: Loop Flows
 Technology / System: TCSC
 Example of application: Power Flow Control
 Loop Flows, or Parallel Path Flows, may be effectively alleviated by the use
 of entirely or partially thyristor controlled series compensation.
 In interconnected power systems, the actual path taken by a transaction
 from one area to another may be quite different from the designated routes
 as the result of parallel path admittance, thus diverting or wheeling power
 over parallel connections. Controlled series compensation is a useful
 means for directing power flows along contracted paths under various
 loading and network configurations. Figure shows parallel path flow
 alleviation by the use of controlled series compensation. With a reduction
 in the direct interconnection impedance between area A and area C, the
 Parallel Path Flow which is routed through area B is decreased.
 Benefits:
 •Increased Power Transfer Capability
 •Additional flexibility in Grid Operation
 •Lower Transmission Losses
 •Improved Transient Stability
 •Improved Grid Voltage Control
 Other applications:
                                                                                more about TCSC and Loop Flow
 •Power Oscillation Damping
 •Subsynchronous Resonance Mitigation

                                                                                                           Back to Overview
                                                                                               Power T&D Solutions              www.abb.com

Power System Technology Navigator (PSTN)                                                                     Saturday, November 19, 2011
Back to Overview                                                                                                                      V. 1.1

 Factors / Phenomena: Oscillations
 Technology / System: TCSC
 Example of application: Power Oscillation Damping
 Thyristor Controlled Series Capacitors may be used to damp bulk power
 system oscillations. A TCSC, in effect, has the ability to increase the
 damping torque (or damping power) on a bulk power system which is
 experiencing angular oscillations between the two terminals of the
 compensated transmission line. It does so by effectively modulating the
 amount of power that flows through the line. When an angular increase
 occurs between the two terminals of a line during an oscillation, the TCSC
 will increase power flow in order to oppose the increase in angle; likewise,
 the TCSC will decrease power flow through the line during the angular
 decrease portion of the oscillation cycle. Figure shows angular oscillation
 prompted by a temporary short circuit on a transmission system. The
 uncompensated system undergoes substantial oscillations following the
 short circuit while the same system with TCSC experiences much improved
 response.
 Benefits:
 •Increased Power Transfer Capability
 •Additional flexibility in Grid Operation
 •Improved Transient Stability
 •Improved Grid Voltage Control
 •Immunity against Subsynchronous Resonance
                                                                                more about TCSC and Power Oscillations
 Other applications:
 •Transient Stability Improvement
 •Interconnections between grids

 •Subsynchronous Resonance Mitigation                                                                        Back to Overview

				
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Description: Generally, the electrical community has come to accept the fact that today's office facilities have an abundance of electronic equipment that produce harmonics. Based on the results of hundreds of electrical system surveys we have determined that the predominant harmonics are triplens; however, a high degree of 5th and 7th harmonics are also present and need to be treated for a more comprehensive solution.