Development Plan of the Slovenian Transmission Grid Inside the UCTE Interconnection

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Development Plan of the Slovenian Transmission
Grid Inside the UCTE Interconnection
Smart Grids Workshop, September 25th, Slovenia
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Current operation state of the Slovenian power
system

• Relatively strong transmission network, 2000 MW
  of peak load and sufficient production capacities
  inside system for domestic demand covering
• In-expensive use of the Slovenian transmission
  network by EU energy market players leads to
  un-secure operation conditions of the Slovenian
  power system and the whole UCTE network.
• Extensive energy power flow from north-east to
  west is concentrated on the Slovenia-Italy border
  and secure power system operation is endangered

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UCTE Energy Balance is Concentrated on the
Slovenia-Italy Border
-7000 MW
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Total Power Flow on Slovenia-Italy Border During
2001
MW 1200 900 600 300 0 -300
TTC
NTC
Power flow
January February March April May
June July August Sept. October
Novem. Decem.
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Total Power Flow on Slovenia-Italy Border During
2005
NTC
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Dynamic simulation results, case 1 SLO-I
tie-lines outage at 1000 MW
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Dynamic simulation results, case 2 SLO-I
tie-lines outage at 1700 MW
NTC
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Possible UCTE splitting due to the large distance
power transfer
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Actual and Administrative Slovenia-Italy
Tie-lines Capacity Contrast

• Thermal capacity of the existing two high-voltage
  lines between Slovenia and Italy, installed on
  the corridor from Divaca substation, is more than
  2000 MW.
• Secure capacity of the existing corridor is due
  to the whole UCTE network limitation (mostly
  because of the un-complete Austrian network)
  about 1200 MW to max.1500 MW, depending on power
  flow control possibilities.
• The actual power flow on Slovenia-Italy border is
  moving around the maximal technical capacity of
  the tie-lines.
• The existing administrative level for network
  trading is just cca. 400 MW and is not in
  accordance with the actual power flows and
  technical limits.

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The reason for discrepancy between actual power
flow and administrative NTC level money game

• Average auction price for the Slovenian-Italy
  cross-border capacity use is pretty high (12
  Euro/MWh) due to existence of the non-expensive
  power sources in the north-east area.
• Slovenia is loosing about 25 million Euro/year
  for its network use due to the too low
  administrative NTC level on Slovenia-Italy border
  this money is collected on other EU borders.
• Merely a cost of the Slovenian transmission
  network active power losses are climbed to 20
  millions Euro/year and almost a half of that
  losses are caused by the transit power flows.
• ELES should cover the costs (losses, maintenance,
  re-dispatching) and risks of energy trading power
  flows by income from domestic energy users.

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Possible Technical Solutions

• Strengthening the transmission network by
  constructing new high-voltage lines, and
• installing devices for active power flow control
  on the certain transmission lines (phase-shifting
  transformers, PST)

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PST Inside Divaca Substation

• ELES already started investment process for 400
  kV and 1200 MVA PST construction inside Divaca
  substation in order to
• control power flows across its network under
  secure technical level assuring thus reliable
  operation of a huge part of the UCTE network,
• control power flow on Slovenia-Italy border close
  to the existed maximal technical limit (1500 MW)
  if the NTC height will follow this technical
  possibilities,
• enable a safe and non-cost re-closure of the
  Slovenia-Italy tie-lines by help of the wide
  range voltage-angle control of the installed PST.
  

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Steps of ELES investment plan on the Slovenian
transmission network
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Conclusion

• ELES steps of its transmission network
  investments will assure
• reliable supply of domestic electric energy
  consumers,
• secure operation of the whole UCTE
  interconnection, not dependent of unpredictable
  EU market processes,
• more fair distribution of market affected costs
  and incomes inside EU TSO partners