Managing transients in isolated Systems with Large Wind Power Penetration Crete experience

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Managing transients in isolated Systems with
Large Wind Power Penetration Crete experience
By John Stefanakis PPC-GREECE
Renewable
Energy Sources Department
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About transients

• Voltage transients (VTs)
• Voltage dips (Short Circuits in the Grid)
• Voltage surges (lightnings, switching operations)
• Frequency transients (FTs)
• Frequency dips (loss of generation)
• Frequency surges (loss of consumption)

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Voltage transients (VTs)

• Induce deferent Voltage changes ?V through out
  the Grid.
• At the point of the Fault Voltage becomes zero.
  Away from the point of the Fault, ?V is inversely
  proportional to the total Thevenins Impedance
  between the point of reference and the point of
  Fault.
• VTs at height Voltage grid influence the whole
  grid but last for a short time (usually less than
  100msec)
• VTs at low Voltage grid influence part of the
  Grid but, because of application of Protections
  Selectivity Principle, they may last for a long
  time (even more than one sec).
• ?V may cause WT trip if the resulting Voltage
  level AND the transients duration exceeds
  certain limits set by the manufacturer of the WT.
• The old generation of WTs is very sensitive
  regarding VTs.
• New Grid-Compatible WTs, promise they can
  overcome the problem.

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Voltage Transients in Isolated Power Systems

• Severe voltage dips because of the weakness of
  the Systems.
• WF outages because of VDs
• Grate number of weather-induced faults
  (lightnings, sea pollution, strong winds).
• Difficulties recovering after a loss of
  generation event because of lack of
  interconnections.

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Typical Voltage dip profile and its propagation
through the System
Voltage profile at 150 kv Linoperamata
Substations Buses during a single-face fault in
face C
Voltage profile during the same fault at 20 kv
Mires Substations Buses (50 Km away of faults
site)
Voltage profile during the same fault at 20Kv
Ierapetra Substations Buses (150 Km away of
faults site)
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WIND-FARMS OUTAGES OWING TO SYSTEM'S VOLTAGE DIPS
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Fault-induced WFs-Outages
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Disturbances 14.02.2004 1042 1052
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Faults in Transmission Lines 1978-2004
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Frequency Transients

• Induce the same Frequency changes ?F all over the
  Grid.
• ?F is proportional to the Load imbalance.
• WTs of Current technology quite resistant to FTs.
• Consequence to the Grid rear but (in case of
  Frequency Dips) fatal to the System because
• Affect all WFs irrespective of their location.
• Load imbalance that causes the FT, is amplified
  by WFs outages leading to unstable performance
  and very probably to Blackout.

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Toward increasing Penetration Small scale
interventions

• Wind Farm level
• Voltage support facilities
• Upgrading Grid connections
• Grid friendly Wind Turbines
• System level
• Strengthening the Grid
• Promoting geo-diversity
• Adopting Supportive infrastructures
• The SCADA System
• Highly qualified personnel in Dispatch Center
• Sophisticated logismic tools

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Typical demand for Voltage deviations
1900
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Typical demand for Frequency deviations
Power
Frequency
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WFs sites
Lasithi Prefecture
Heraklion Prefecture
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Toward increasing PenetrationThinking big

• The Energy Storage Systems
• Pump Storage Systems
• Flying Wheels
• Compressed air
• Batteries (Redox Flow Batteries)
• The interconnection with the Mainland System