Macedonia: Electricity flow directions and interconnections critical elements

19. January 2016. / SEE Energy News

Macedonia power flow directions with its neighbors Serbia, Bulgaria, Greece, Albania and Kosovo show certain limitations and critical network elements. Being a net electricity importer Macedonia realized several projects and analysis for improving its capacities.

Macedonia is part of SMM block together with Serbia and Montenegro. Macedonia is an importer of electricity.

Critical network elements in Macedonian transmission system with respect to cross-border exchanges are:

OHL 110 kV Skopje 3 – Skopje 4 OHL 110 kV TETO – Skopje 4 TR 400/110 kV Štip

MEPSO doesn’t consider the 110 kV network as a limiting elements for the NTC values, but evaluates limitations in the 400 kV network only.

OHL 110 kV Skopje 3 – Skopje 4 may be overloaded during TPP Oslomej low production or out of operation situation. This line may be relieved by disconnection of the OHL 110 kV Skopje 3 – Saraj.

OHL 110 kV TETO – Skopje 4 may be relieved by bus-bars 110 kV connection in the SS Skopje 1 or by connection of the OHL 110 kV Centralna – Jug Nova.

Overloading of the TR 400/110 kV Štip may be solved by local network 110 kV uncoupling. This problem occurs when high transits flow to Macedonia from Bulgaria and 110 kV generators in Macedonia are engaged poorly. In reality, transits go to Greece over Macedonian network and transformer 400/110 kV in the Štip substation will not be overloaded.

For the direction of power flows from Macedonia to Serbia and Kosovo, the NTC values are limited by maximum generation shifts in the Macedonia, Serbia and Kosovo area to 681 MW, evaluating the Macedonian side, and 441 MW, evaluating the Serbian and Kosovan side. Network limitations in Macedonia, Serbia and Kosovo for these ranges of power exchanges are not visible at the model, except for one network limitation in the 110 kV network of Macedonia, related to the OHL 110 kV TETO – Skopje 4, which gets overloaded as a consequence of an OHL 400 kV Skopje 5 – Kosovo B outage.

For the direction of power flows from Kosovo and Serbia to Macedonia, evaluating all 400 kV, 220 kV and 110 kV network elements on the Macedonian side, the NTC value is set to 600 MW. It is limited by the OHL 110 kV Skopje 3 – Skopje 4, which gets overloaded as a consequence of an OHL 110 kV G. Petrov – Skopje 1 outage. Evaluating the Kosovan and Serbian side and network 400 kV, 220 kV and 110 kV, a limitation appears concerning the 110 kV line Valjevo – Kosjerić. The NTC values for this direction of power exchanges may be increased up to 870 MW if we ignore 110 kV network elements in Macedonia, Serbia and Kosovo. A new limitation will appear on the OHL 220 kV Pljevlja – Bajina Bašta as a consequence of an OHL 220 kV Bajina Bašta – Požega outage.

For the direction of power flows from Macedonia to Greece and monitoring 400 kV, 220 kV and 110 kV networks on the Macedonian side, the NTC value is set to 755 MW. It is limited by the OHL 110 kV TETO – Skopje 4, which is jeopardized by an outage of the OHL 110 kV Skopje 1 – Kumanovo 1. Ignoring the 110 kV network in Macedonia, the NTC values are limited by maximum generation shift in Macedonia to 879 MW.

For the direction of power flows from Greece to Macedonia, evaluating all 400 kV, 220 kV and 110 kV network elements on the Macedonian side, the NTC value is set to 212 MW. It is limited by the OHL 110 kV Skopje 3

– Skopje 4, which gets overloaded as a consequence of an OHL 110 kV G. Petrov – Skopje 1 outage. The NTC value for this direction of power exchanges may be increased up to 636 MW if we ignore 110 kV network elements in Macedonia. No new critical network elements have been noticed for the maximum level of power exchange due to maximum generation shift in Macedonia.

For the direction of power flows from Bulgaria to Macedonia and evaluating the internal transmission network of Bulgaria, the NTC value would be limited to 267 MW due to weaknesses in the 110 kV network in the Dobrudzha area. Ignoring limitations in the 110 kV network of Bulgaria, bottleneck appears concerning the OHL 220 kV Plovdiv – Aleko due to an OHL 400 kV Maritza East 1 – Plovdiv outage. It limits the NTC value up to 523 MW. Monitoring interconnection lines only and ignoring the problems in the Bulgarian internal network, the NTC value could be increased significantly, up to 1185 MW, without any limitations but due to maximum generation shift in Macedonia.

For the same direction of power flows but evaluating network elements on the Macedonian side, the NTC values could be increased up to 855 MW. It would be limited by possible overloading of the OHL 110 kV Skopje 3 – Skopje 4 as a consequence of an OHL 110 kV G.Petrov – Skopje 1 outage. Further increase is possible up to 1074 MW if we ignore the Macedonian 110 kV network, the new critical element becomes 400/110 kV transformer Štip that is jeopardized by the interconnection line 400 kV Dubrovo – Štip outage. Monitoring tie-lines only, the NTC value of 1186 MW could be reached, limited by maximum generation shift in Macedonia.

Based on the lower NTC value between both sides, the final NTC value for the Bulgaria to Macedonia direction of power exchange is set to 267 MW if we evaluate internal networks. It is limited by the 110 kV network in the Dobrudzha area. The NTC value is 523 MW if we ignore 110 kV networks and is limited by the OHL 220 kV Plovdiv – Aleko. The NTC value is 1185 MW if we evaluate tie-lines only, without any network limitations.

For the direction of power flows from Macedonia to Bulgaria, and evaluating all 400 kV, 220 kV and 110 kV network elements on the Bulgarian side, the NTC value is set to 282 MW. It is limited by the 400/110 kV transformer in the SS Plovdiv, which is jeopardized due to an outage of the parallel transformer. For the same direction of power flow and evaluating tie-lines on the Bulgarian side only, the NTC value is increased up to 413 MW due to maximum generation shift in Macedonia.

 

For the direction of power flows from Macedonia to Bulgaria, monitoring the 400 kV, 220 kV and 110 kV networks of Macedonia, limitations appear due to OHL 110 kV TETO – Skopje 4 overloading when the NTC value is 288 MW as a consequence of an OHL 110 kV Skopje 1 – Kumanovo 1 outage. The thermal rating of this 110 kV line is set to 157 MVA. The NTC value would be increased up to 412 MW if limitations in the 110 kV network of Macedonia are ignored, due to maximum generation shift in Macedonia, transmits Serbia-energy.eu

There is no direct transmission line between Macedonia and Albania and EBRD is currently assessing the credit line for this project. By providing the Macedonian side of the first interconnection between FYR Macedonia and Albania, the Project provides the missing link in the initiative to establish an East – West electricity transmission corridor between Bulgaria, FYR Macedonia, Albania, Montenegro and Italy.  The section between Bulgaria and FYR Macedonia has been completed. Albania and Montenegro are connected through a new 400kV line and the construction of the submarine cable between Italy and Montenegro is underway, supported in Montenegro through the Lastva – Plejvlja Transmission Line Project.

The indicative annual NTC value for the Macedonian/Kosovan border was set to 250 MW for both directions in 2012, 200 MW (MK to RS direction) and 300 MW (RS to Macedonia direction) in 2013, and 100 MW (MK to RS direction) and 150 MW (RS to Macedonia direction) in 2014.

The indicative annual NTC value for the Macedonian/Greek border was set to 150 MW for the MK to GR direction and 300 MW for the GR to MK direction in 2012, 200 MW (MK to GR direction) and 300 MW (Greece to Macedonia direction) in 2013, 250 MW (MK to GR direction) and 350 MW (GR to Macedonia direction) in 2014.

The indicative annual NTC values for the Macedonian/Bulgarian border, as well as month-ahead values for all Macedonian borders, were not published by ENTSO-E.

Day-ahead NTC values in January 2014 were set to:

Macedonia/Bulgaria border50 MW (for MK to BG direction) and 150 MW (for BG to MK direction) Macedonia/Greece border170 MW (for MK to GR direction) and 350 MW (for GR to MK direction) Macedonia/Kosovo border250 MW (for MK to RS direction) and 700 MW (for RS to MK direction), transmits Serbia-energy.eu

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