| Abstract | Svrha ovog rada je na temelju četiri simulacijska slučaja prikazati ukupne gubitke sustava, kako radne tako i reaktivne te zamjenom dva nadzemna voda podzemnim kabelima prikazati gubitke i isplativost jednog naspram drugog te prikazati prednosti i nedostatke oba slučaja. Zamjenu nadzemnog voda podzemnim kabelom smo vršili upravo kako je opisano iznad zamjenom parametara, za zadanu duljinu voda. Važno je za napomenuti da je vod 1-2 najviše opterećeni vod u sustavu te kako je vod 3-4 najmanje opterećeni vod u sustavu te to možemo i vidjeti iz tablice 5.4. po radnim i reaktivnim gubitcima.
Iz gore navedenog te i iz rezultata simulacije možemo zaključiti da kabeli imaju nešto niži djelatni otpor što nije uvijek slučaj, no u našoj simulaciji je te su stoga ukupni radni gubitci sustava manji korištenjem podzemnog kabela nasuprot nadzemnog voda. Isto tako, zbog velikog kapaciteta podzemnog kabela dolazi do generiranja reaktivne snage u kabelima, a pogotovo dolazi do izražaja kao što možemo vidjeti u drugoj simulaciji kada je kabel nisko opterećen tj. dolazi do neželjene pojave u sustavu, a to je povećanje napona na kraju voda odnosno dolazi do pojave Ferantijevog efekta. Iz navedenog te i iz rezultata simulacije se da zaključiti kako je znatno isplativije koristiti nadzemni vod umjesto podzemnog kabela za mreže koje su nisko opterećene zbog znatno većih gubitaka uslijed kapacitivnih struja te generiranja reaktivne snage u mreži koje dovodi do nepovoljnog povećavanja napona na kraju voda. Korištenjem podzemnog kabela u vodovima koji su opterećeni nazivnom snagom ili približno nazivnom kapacitivne struje dolaze manje do izražaja te se samim time i smanjuju gubitci te smanjuje povećanje napona na kraju voda. Zaključno, oba slučaja, i nadzemni vod i podzemni kabel imaju svoje prednosti i nedostatke. Nadzemni vod generira veće radne gubitke u sustavu no jeftiniji je za održavanje te popravak, dok podzemni kabel zbog znatno većeg kapaciteta generira veće reaktivne gubitke u sustavu te uzrokuje pojavu Ferantijevog efeketa na kraju voda, no ima manje radne gubitke od nadzemnog voda te ima manji utjecaj na okoliš pogotovo u visoko naseljenim mjestima. |
| Abstract (english) | The purpose of this paper is to show the total losses of the system, both working and reactive, based on four simulation cases, and by replacing two overhead lines with underground cables, to show the losses and profitability of one against the other, and to show the advantages and disadvantages of both cases. We replaced the overhead line with an underground cable exactly as described above by replacing the parameters, for the given length of the lines. It is important to note that line 1-2 is the most loaded line in the system, and that line 3-4 is the least loaded line in the system, as we can see from table 5.4. by working and reactive losses.
From the above and from the results of the simulation, we can conclude that the cables have a slightly lower effective resistance, which is not always the case, but in our simulation it is, and therefore the total operating losses of the system are lower when using an underground cable as opposed to an overhead line. Likewise, due to the large capacity of the underground cable, reactive power is generated in the cables, and it is especially pronounced as we can see in the second simulation when the cable is under low load, i.e. an unwanted phenomenon occurs in the system, which is an increase in the voltage at the end of the line that is, the Ferranti effect occurs. From the above and from the results of the simulation, it can be concluded that it is significantly more profitable to use an overhead line instead of an underground cable for networks that are lightly loaded due to significantly higher losses due to capacitive currents and the generation of reactive power in the network, which leads to an unfavorable increase in the voltage at the end of the lines. By using an underground cable in lines that are loaded with rated power or approximately the rated capacity, capacitive currents come to the fore less, thus reducing losses and reducing the increase in voltage at the end of the lines. In conclusion, both cases, the overhead line and the underground cable have their advantages and disadvantages. The overhead line generates higher operational losses in the system, but is cheaper to maintain and repair, while the underground cable, due to its significantly higher capacity, generates higher reactive losses in the system and causes the appearance of the Ferranti effect at the end of the line, but has lower operational losses than the overhead line and has a smaller impact on the environment, especially in highly populated areas. |
