Utredning av hållbar elnätstruktur för tät blandstad
Examensarbete på grundnivå
Elektroteknik 180 hp (högskoleingenjör)
When building a new area in a modern dense city with a mix of residential and commercial buildings, it can be difficult to use the traditional type of distribution grid with a large part of low voltage level for various reasons. The main purpose is therefore to investigate under what circumstances it is more beneficial to build the power grid with mainly medium voltage level and built-in substations instead of external substations. The investigation is being done considering the distribution grid of Göteborg Energi and investigates the possibilities of building medium voltage level regarding some given variables such as cable length, transformer size and load density, i.e. power per area. The characteristics which are being investigated are reliability, space efficiency, environmental impact, cost of investment, operation and maintenance and also losses. Calculations are made based on three different distribution alternatives, low voltage, medium voltage loop distribution and medium voltage radial distribution. To perform the calculations and comparisons a model has been created which calculates the combinations of the given variables. Distribution with mainly medium voltage level gives less losses, takes up less space and causes less CO2 emissions. It also has better reliability than low voltage, especially the case with loop distribution. The built-in substations have a downside of having a big cost to reduce the electromagnetic field exposure, this extra cost can make this alternative more expensive. There may also be an additional cost for obtaining the rights to place lines. What determines the best distribution alternative, besides the cost, is how difficult it is to find places for external substations and extensive placement of low voltage cables. Therefore, it is hard to give an exact answer to at what load density the built-in substations are better, because a certain figure on load density may refer to higher buildings, but still with enough space in between them for external substations, or it can refer to lower buildings with tighter placement where there is no room for external substations.
Elkraftteknik , Electric power engineering