The challenges facing low voltage grids are rising as an increasing number of domestic houses transition from fossil fueled heating to electricity based heating. Several environmental goals and visions have the same transition from fossil based power to electricity based power in mind for the transportation sector. One of the most important tools for this transformation is widely regarded to be the electric vehicle. With the demands of the electric vehicle pressuring the power grid, several questions arise regarding the growth of the electric vehicle market and what repercussions it may have on the grid. This paper focuses on a typical low voltage grid in southern Sweden and what effects a growing electric vehicle market may have on it. Through computer-assisted simulations based on several future scenarios regarding the EV market, this paper finds that few modifications and reinforcements are needed on this particular grid within the next 10 to 15 years. After this timeframe the voltage drop becomes a serious concern and should be addressed. / Utmaningarna som lågspänningsnät står inför växer i takt med att fler bostäder övergår från fossilbaserad till elbaserad värme. Flera miljösatsningar och visioner ämnar pådriva samma förändring inom transportsektorn och eldrivna fordon anses som ett av de viktigaste verktygen för att genomföra detta. Med ytterligare potentiella påfrestningar på lågspänningsnäten från de elektriska fordonens behov ställs frågan hur utbredd den elektriska fordonsmarknaden kommer att bli och vilken påverkan den kommer ha på elnäten. I detta arbete belyses ett typiskt lågspänningsnät i södra Sverige och vilka effekter elfordonens utbredning kan tänkas ha på den. Genom datorstödda simuleringar enligt flera olika prognosscenarion finner arbetet att relativt få förändringar och förstärkningar behöver göras på det analyserade nätområdet inom ett tidsspann på ca 10 till 15 år. Efter detta tidsspann orsaker lasterna ett högt spänningsfall i det aktuella nätet som bör åtgärdas.

Samhället står inför stora utmaningar för att globalt, regionalt och lokalt minska de klimat- och miljömässiga avtrycken till följd av antropogena aktiviteter. Transportsektorn står globalt för drygt en fjärdedel av utsläppta växthusgaser vilket varit en bidragande drivkraft till miljöavtal som kräver alternativa bränslen, reducerad användning och energieffektiviseringstekniker för att uppnås. Sverige har globalt den högsta andelen förnyelsebara bränslen (23 % år 2019) men tros, enligt trender, skifta till en mer elektrifierad fordonsflotta, som del i att uppnå miljömålen för transportsektorn. Ackumulerat effektuttag för laddbara fordon har visat sig orsaka försörjnings- och distributionsutmaningar i elnätet vilket detta arbete djupdykt kring. Syftet med detta arbete är att på en tidigare minimalt utforskad stads-skala utvärdera en stads utsatt- och robusthet gentemot olika prognostiserade elektrifieringstrender för 2030 - vilket gjorts på Tekniska verken i Linköping AB:s nät. Två scenarier, ett förutsägande och ett explorativt, har utifrån litteratur och omvärldsgranskning skapats i kombination med simulering på Linköping stads befintliga elnät för att uppskatta nya belastningsgrader och spänningsfall. Med det explorativa scenariot som referens har även framtida "smarta-nät"-lösningar (ellagring, Vehicle-to-grid/house, flexibilitetsmarknader m.fl.) demonstrativt visat potentialen hos laststyrning som alternativ till traditionell elnätsförstärkning. Förutom rent eltekniska aspekter och statistiska trender har även externa utvecklingsfaktorer, till följd av omställningen av transportsektorns multidimensionella och komplexa påverkanssamband, utvärderats. Utblickar mot den globalt ledande norska elbilssituationen, institutionella styrmedel, alternativa bränslen samt socio-tekniska och kulturella värderingar har likaså vägts in under diskussion och analys. Resultaten och inverkande omvärldsanalyser indikerar, utifrån fallstudiens omständigheter, en mild utvecklingstrend till 2030. Omkring 12 % av personbilsflottan, samtliga bussar i tätortstrafik och få tunga fordon förväntas elektrifieras och tros belastningsmässigt vara högkoncentrerat i villaområden med pendlingsavstånd och hög medelinkomst. Effekten av detta kan leda till lokalt överbelastade lågspänningsnät som primärt bör lösas med laststyrning genom ellagrings- eller V2H-tekniker innan omfattande nätförstärkning. Tekniska verken som nätägare rekommenderas framöver aktivt följa elbilstrenden i Linköping och omvärlden för att tidigt förebygga konsekvenser likt de resultaten påvisade hos det stresstestande scenariot.

With an ever growing demand for electricity, it is tough to know which challenges will be the most pressing and which solutions will be appropriate to implement in different cases. This thesis utilizes simulations of three low voltage grids to see which part of the grid is most vulnerable, to which extent grid reinforcement is needed to solve voltage and load problems, and what amount of demand flexibility services would be an adequate substitute to grid reinforcement. The three grids consists of a meshed grid in a suburban area, a radial grid in the city and a radial grid in the countryside. The grids are subjected to full penetration of electric vehicle chargers in a winter setting and full solar power penetration in a summer setting. The results indicate that the transformer is overloaded in both residential grids, although even more so in the meshed grid as opposed to radial grid wherein the cables are most overloaded. The countryside grid had some voltage problems in the summer, but were overall not affected notably. The conclusions were that the increase in electric vehicle chargers will be the most impending challenge and that grid reinforcement will be necessary in the long run but that demand flexibility services are a viable option in the meantime. The transformer would also need an upgrade in both residential grids.

In 2018 the Swedish government introduced a new legislation for the electricity meters installed in the low voltage networks. The legislation includes, among other things, that the electricity meters should be able to measure the current and voltage per phase with a time resolution of one hour or 15 minutes. To meet the new requirements Falu Energi & Vatten have started a rollout of new electricity meters in their low voltage networks. In addition to this, electricity meters have also been installed in a few secondary substations in Falun. The overall purpose of this project was to investigate what the data from the new electricity meters can be used for and what the benefits are with having metering equipment in secondary substations. Data from secondary substations can be useful when dimensioning the grid or when analysing power losses. During the project, data was collected from one secondary substation and the underlying low voltage network. The parameters current and voltage were measured per phase with a time interval of 15 minutes. The data was used in three different investigations. The results from two of them indicated that the network information system that Falu Energi & Vatten uses for dimensioning tends to overestimate the power consumption and the voltage drop between the secondary substation and the low voltage customers. In the last investigation a method for localising non-technical power losses was evaluated. The result indicated that the method was not suitable for the purpose.

The number of solar panel systems and electric vehicle charging in the low voltage grid is increasing rapidly, due to climate- and environmental targets. These nonlinear loads inject harmonics into the grid, which could impact power quality as well as the wear and life of power grid components, such as transformers and cables. The Swedish network operator Ellevio wants to investigate the possible effects that can arise from a largescale introduction of this equipment in the grid, in terms of harmonics. The aim of this master thesis has been to evaluate the compatibility of equipment emission standards and requirements for power quality, and through different calculation methods assess the potential impact from high penetration of devices in the same network. The results show that converters of both EV and PV are able to keep emission levels well below the equipment standard limits. Even by full penetration of a network the aggregated effect of these loads will not alone have a significant impact on neither power quality nor components in terms of wear, losses or capacity. However, in networks experiencing unusually high background levels in combination with high emissions from other loads, the PV and EV emissions could be a contributing factor to a state where individual transformers would be affected or single harmonic voltage limits would be violated. This is considered a very rare case, and thus not something that would serve as a basis for the dimensioning of the low voltage grid. Instead, increased knowledge will help assessing such a scenario and give better support for solving the individual cases that do arise.

The number of electrical vehicles in Sweden are increasing faster for every year and the demand of charging them at home is growing as well. This requires high delivery reliability and a stable low-voltage distribution grid. In this master thesis three different low-voltage networks are modelled and simulated together with load which corresponds home charging of electrical vehicles (EV) to analyse if the grid is able to handle these kinds of stresses. Information of the different grids were gathered from Falu Energi & Vatten and modelled in Matlab together with EV charging loads generated in a separate program. The electricity consumption data used in the simulations were measured at the transformer in each grid. A regression analysis of the consumption data were preformed to calculate values which corresponds to a worst case scenario. The results show that the low-voltage distribution grid in Falun is well dimensioned and can handle these possible future loads even in the worst constructed scenario.

In some electrical facilities for underground mining, IT-system grounding is used for processes of high priority. This report explains why such systems are used in these kinds of environments, what happens when single-line-ground faults occur and how does the fault protection and monitoring devices handle those faults in accordance to current regulations and standards.An IT-system imply that the neutral point of a transformer is completely or partially connected to earth and exposed conductive parts are bolted directly to ground.IT-coupled networks have been implemented in some mining industries to prevent long and unnecessary down time of production. This is achieved by allowing a single-line-ground fault without interfering with the operation. According to current regulations and standards a single-line-ground fault is allowed on the term that continuously monitoring the insulation of the system, alarm in presence of a fault and remedy as soon as possible.During a single-line-ground fault the artificial neutral point of the system will be displaced relative earth and different amounts depending on the resistance in the fault location. When a bolted single-line-ground fault occur, the faulty line will adopt earth-potential. Between a healthy line and earth, the potential difference reaches line-line voltage and even more than that, depending on the fault-resistance. This entails a higher requirement of the insulation level of the equipment installed in an IT-system. The fault current that emerges in an IT-system depends especially of the capacitive connection between the line conductors and earth, but it is reduced by the resistance in the fault location.In the existing electrical system of the underground mine, insulation-monitoring-devices where installed. These where setup with two alarm limits, one for alarming and the second for release of the circuit breaker feeding the main busbar, if the fault remains for longer than two hours.The insulation monitoring in the existing electrical system, where supplemented with residual-current-monitoring, setup to alarm for residual currents exceeding 60 mA. One presumption the residual-current-monitoring devices requires to be able to detect a fault, is that the upstream installed cable network is widespread enough, that the capacitive connection causes a big enough current to flow.In this report the characteristics of an IT-network were verified with calculations. Simple calculations of the minimum cable length were also made, when using residual-current-monitoring.The conclusion for the existing electrical system in the underground mine, is that the IT-system network of it, is installed in accordance with current regulations and standards in Sweden.

When the low voltage electric grid is dimensioned electric loads are predicted by analyzing the area by certain factors such as geographical data, customer type, heating method etc. So far, the charging of Plugin Electric Vehicles (PEVs) is not considered as one of these factors. Approximately 30% of the distribution grid in Sweden is projected to need reinforcements due to the increased loads from PEVs during winters if the charging isn’t controlled. In addition to this Stockholm face the problem of capacity shortage from the transmission grid, limiting the flow of electricity into the city. This research is therefore conducted to analyze the impact that the increase of PEVs will have on the distribution grid in the future. This thesis simulates the electric grid for three substations located in Hammarby Sjöstad by using power flow analysis and electric grid data from 2016. To approach this problem a method to disaggregate the total power consumption per substation into power consumption responding to each building was developed. In addition to this the number of PEVs in the future was projected. Nine different scenarios were used to compare different outcomes for the future, namely the years of 2025 and 2040. In order to simulate the worst possible case for the electric grid all the PEVs were assumed to be charged at the same time, directly when arriving home on the Sunday when the power demand peaks in 2016. The results indicate that PEVs can have a considerable impact on the components of the low voltage distribution network and controlled charging should be implemented. By examining the impact on the simulated electric grid from the different scenarios the limit of PEV penetration is found. In the area of Hammarby this limit seems to be around 30 % of the total cars if there is no controlled charging. Without any controlled charging the peak power demand increases by 30% with a 30% share of PEVs, which is projected to happen in 2025. In 2040 when share of PEVs is projected to be about 95% the peak power is instead increased by more than 100% which shows the impact that PEVs can exert on the electric grid. Utilizing a simple method of controlled charging where the PEVs are instead charged during the night when the power demand is low, the peak power is not increased at all. This also results in the small cost benefit for PEV owners since the electricity is cheaper during the night and controlled charging can therefore save about 15% of the electricity charging cost. However, the main savings are for the grid owners since the need to reinforce the grid is heavily reduced. In addition to this the power losses are reduced heavily from about 14% down to 5% in the electric grid that is simulated. / När dimensioneringen av distributionsnätet utförs analyseras området genom att räkna med elektriska laster som till exempel kan bero på geografiska data, typ av konsument, uppvärmningsmetod etcetera. Än så länge har laddningen av elbilar (PEVs) inte varit en av dessa faktorer trots den förväntade tillväxten av elbilar. Ungefär 30% av Sveriges distributionsnät förväntas behöva förstärkningar på grund av den ökade elkonsumtionen från elbilar under vintrarna om laddningen inte kontrolleras. Utöver detta står Stockholm inför problemet med effektbrist från elöverföringsnätet. Denna uppsats genomförs således för att analysera påverkan från elbilar på fördelningsnätet i framtiden. Denna masteruppsats simulerar det elektriska nätet för tre nätstationer i Hammarby Sjöstad genom en analys av effektflödet. En metod för att disaggregera elkonsumtionen per nätstation ned till elkonsumtionen per byggnad utvecklades och antalet elbilar i framtiden uppskattades. För att utvärdera elbilars påverkan skapades nio olika scenarion för framtiden genom att undersöka hur det kommer att se ut år 2025 och år 2040. Genom att anta att laddningen av alla elbilar i området sker samtidigt, samma tid som den maximala förbrukningen av el sker under en söndag 2016, analyseras det värsta möjliga scenario för det elektriska nätet. Resultaten visar att elbilar kan ha enorm påverkan på de maximala lasterna för ett lågspänningsnät och därför kommer kontroll av laddningen behövas. Genom att undersöka elnätets påverkan i de olika scenariona uppskattades gränsen för hur många elbilar det modellerade elnätet klarar av. I Hammarby Sjöstad ligger denna gräns på ungefär 30% elbilar. Utan kontrollerad laddning ökar maxlasten med 30% år 2025 då antalet elbilar förväntas vara 30% av alla bilar i Hammarby Sjöstad. År 2040 då antalet elbilar uppnår ungefär 95 % av alla bilar ökar maxlasterna med mer än 100% vilket visar den enorma påverkan elbilar kan ha på elnätet. Genom att använda en simpel modell av kontrollerad laddning som består av att flytta laddningen från eftermiddagen till natten, då förbrukningen av elektricitet är låg, ökar inte maxlasten för dygnet alls jämfört med scenariot utan elbilar. Detta resulterar också i besparingen av elektricitetskostnad för elbilsägaren med cirka 15% eftersom elektriciteten ofta är billigare under natten jämfört med kvällens elpriser. Detta är dock små summor jämfört med besparingar elnätsägarna kan göra då elnätet inte behöver förstärkas lika mycket som skulle behövas utan kontroll av laddningen. Utöver detta så sänks även förlusterna av elektricitet i det simulerade nätet från 14% ned till 5% genom att utnyttja denna modell av kontrollerad laddning.

The thesis work was carried out within the Swedish Transport Agency's ERTMSproject to assist in deciding on the power supply of the facilities along the railways related to the project. This work applies to areas such as the implementation of the new rectifier, the Rectiverter, and power supply design with focus on redundancy and the overall electricity quality. The work was carried out by processing data from one week's power quality measurement at one of the signal plants where there was an installed Rectiverter. The results were set against current standards and causes of events discussed. The work indicates that the tested facility where power quality was measured meets the applicable standards. However, measures can be made to increase the efficiency of the facility, concerning both redundancy and direct power losses. This refers to the choice of power supply at facilities around the country and the conversion of AC to DC before the UPS and DC to AC-voltage after UPS to the Rectiverter. In chapter one terminology and abbreviations are listed. Chapter two contains an introduction to the report where background, purpose and objectives are formulated. Theory of power quality concepts, data processing, prevailing standards and information about the facilities of the Swedish Transport Administration can be found under chapter three. In chapter four, the methodology used for the power quality measurement and how it was carried out is presented. This includes the collection of sources, used equipment, practical set-up and used method for analysis. In chapter five, the results from the measurement are presented, which are then discussed further in the discussion (chapter six). The report is then summarized with conclusions and suggestions for further work in chapters seven and eight.