Flow-based coordinated auctioning (CA) is crossborder transmission capacity allocation mechanism. The SouthEast European (SEE) Transmission system operators (TSOs) launched the investigation of this method, based on better representation of physical behavior of interconnected electric systems than those widely used on most of the European borders. CA uses flow-factors (PTDF -Power Transfer Distribution Factors) to convert the commercial exchanges into their physical influence on the cross-border flows, and Border Capacities (BC) as physical limitations for those flows. The goal of this paper is to conduct a numerical comparison between different methods used for PTDFs calculation.

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Original scientific paperThe description and analysis of phenomena that occur in case of disconnection of fault currents with generator circuit breakers after asynchronous connection of a generator and difficulties encountered during the process of disconnection are given in the paper. Generally, the biggest problems occur during the interruption of the fault when the direct current component (DC) is very high. DC component value depends on the type and conditions of the fault. For this purpose, a real study case with accidental asynchronous connection of generator via 400 kV circuit breaker is given from the Kosovo Power System which seriously damages the circuit breaker. For the purposes of this analysis, the real case situation has been also modelled with software such as: EMTP/ATP and PSS/E. It is important to emphasize that during using the high speed AC circuit breaker in power system it is not always the advantage to make successful disconnection of failures through High Voltage Circuit Breaker due to the presence of the high value DC component and the delay of passing of AC current through zero. For the generator the most important is detail analysis of behaviour of the generator in network in order to specify proper circuit breaker that can cover all circumstances that can happen in the system so to be able to protect the generator, step up transformer and other equipment. Keywords: AC component; asynchronous connection; DC component of fault current; high voltage generator circuit breaker; short circuit Struja kvara uslijed asinkronog priključka generatora na mrežu i njen utjecaj na visokonaponski prekidač s plinom SF6Izvovorni znanstveni članak U radu su dani opis i analiza fenomena koji se događaju u slučaju isključenja struje kvara generatorskim prekidačima nakon asinhronog priključenja generatora i poteškoćama tokom procesa isključenja. Općenito, najveći problemi se javljaju tokom prekida kvara kada je komponenta istosmjerne struje (DC) vrlo visoka. Vrijednost DC komponente ovisi o vrsti i uvjetima kvara. U cilju analize ovog fenomena, u radu je analizirana situacija slučajnog asinhronog priključenja generatora preko 400 kV prekidača u elektroenergetskom sustavu Kosova koja je dovela do oštećenja prekidača. Za potrebe analize, ovaj slučaj je modeliran u softverskim paketima EMTP/ATP i PSS/E. Važno je napomenuti da uporaba brzih AC prekidača u elektroenergetskom sustavu nije uvijek prednost za omogućavanje uspješnog isključenja kvara pomoću visokonaponskog prekidača, zbog prisustva DC komponente s visokim vrijednostima i zakašnjenja prolaza AC struje kroz nulu. Za generatore je najvažnija detaljna analiza ponašanja u mreži kako bi se odredile optimalne karakteristike prekidača u svim okolnostima koje se mogu dogoditi u sustavu, kako bi se omogućila pravilna zaštita generatora, step up transformatora i druge opreme.Kljućne rijeći: asinkrono priključenje; generatorski prekidač visokog napona; komponenta istosmjerne struje kvara (DC); komponenta izmjenične struje (AC); kratki spoj

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