project for 400 kv interconnection between power systems of ...

More documents

Recommendations

Info

Study for Optimization of Connection Point of new 400 kV Interconnection to SerbiaTransmission capacitiesIn calculation of transmission capacities, the exchange of energy can be simulated betweenfollowing areas:– TBC for northern Macedonian interface[BUL + SER + MN] ↔ [MKD + GRE +ALB]– TBC for southern Macedonian interface[MKD + BUL + SER + MN] ↔ [GRE +ALB]ROBIHSRMNBGMKALGRFigure 8. Definition of import/export areas for TBC calculationIn most of the cases, during calculation of transmission capacities, critical event is outage of onecircuit of double circuit 400 kV line Sofia West – C. Mogila, which leads to overloading of the secondcircuit. Only in calculation of transmission capacities of the southern interface in variants 3a and 3b, outageof the new 400 kV interconnection Filippi (Greece) – Maritza East (Bulgaria) can cause overloading of theplanned 400 kV interconnection Kexru (near to Filippi, Greece) – Babaeski (Turkey).Analyses show that bottlenecks of the cross border transmission are located in the eastern parts ofthe regional transmission network. Building new interconnections will strengthen the network and the majorpart of the transits will be drawn in the middle part, through Macedonian network. Consequently, flows onoverloaded critical lines are reduced and transmission capacities of the network are increased.Variant 3b has the smallest influence on increasing TBC, in reference to basic network topology.Variant 3a has the biggest growth of TBC on the northern interface of 259 MW. This variant causes thebiggest increase of the capacity for the whole region also, for over 500 MW. Variant 2 causes the biggestincrease of the capacity on the southern interface for over 187 MW.10
Study for Optimization of Connection Point of new 400 kV Interconnection to Serbia700TBC [MW]North interconnection1000TBC [MW]South interconnection650950600900550850500800450750400var 0 var 1 var 2 var 3a var 3b var 3c700var 0 var 1 var 2 var 3a var 3b var 3cFigure 9. Graphical representation of transmission capacitiesShort-circuit currentsFor normal operation of the power system it is necessary to fulfill following condition: maximumvalue of short-circuit current in each bus of the system must be smaller in reference to breaking current of thedevices installed in that bus. During the planning, the maximum level of the short-circuit faults is checked inorder to confirm compatibility of existing equipment and dimensioning the new equipment, using mediumterm forecast model. The calculations are made according to an optimistic scenario for the expansion of thesystem, supposing that all major projects for the expansion of the network are already released.The biggest short-circuit current are expected at 110 kV busbars in SS Skopje 1 and SS Skopje 4.Variant 1 has the maximal growth of 3-phase and 1-phase fault in Skopje 1 and Skopje 4, their values are2.4 kA/ 2.3 kA and 1.9 kA/1.8 kA, respectively. 1-phase fault on 110 kV busbars in SS Skopje 1 is 38.3 kA.This value can be considered critical because it almost reaches rated breaking power of high voltageequipment in the substation. Primary reason for high value of short circuit fault is high density of 400 kVlines and production units at/near this bus (in variant 1 there are three interconnections at Skopje 5 * ). Thisvalue is unacceptably high and is recommended to avoid variant 1 as a potential solution.3.4. ECONOMICAL CRITERIA FOR EVALUATION OF VARIANTSEconomical comparison of the variants is done with the profitability index method bydetermination of cost/benefit ratio. Costs/benefits of the variants are converted to equivalent annual valueand profitability index r is calculating.r =B( A+O).B (benefit) is equivalent benefit per year from:– Reduced losses of active power and energy;– Revenue from the increased transmission capability due to revenue of renting transmissioncapacity in cases of congestion;* In fact, Skopje 5 and Skopje 1 is the same substation, where Skopje 1 refers to 110 kV busbars andswitchyards and Skopje 5 refers to 400 kV busbars and switchyards. Skopje 5 and Skopje 1 are connected with two400/110 kV autotransformers, with 300 MVA each unit.11
Page 1 and 2: MACEDONIAN TRANSMISSION SYSTEM OPER
Page 3 and 4: Study for Optimization of Connectio
Page 9: Study for Optimization of Connectio
Page 15: Study for Optimization of Connectio

project for 400 kv interconnection between power systems of ...

Create successful ePaper yourself

Delete template?

Save as template?