How it works: overhead lines 2 How it works: overhead lines In our society, electricity is undeniable. At home, we simply need a wall socket and we are free to power or charge our electric appliances. However, to make sure that electricity flows without interruption, it must be transported from the point of generation to the point of consumption. How does the current arrive there? What points of contact does it pass through before eventually arriving at the home? Energy is transported from the generator to the consumer via power lines and switchgear. 50Hertz operates the overhead lines at its highest voltage level. These “electricity highways” are the backbone of the energy supply. They enable a reliably functioning national and European electricity market and ensure that ever more renewable energy is integrated into the power system. By 2030, energy from renewable sources should cover 65 percent of the German consumption of electricity. Germany’s federal government agreed to this in 2018. At the time, over 56 percent of the electricity in the 50Hertz grid area was already generated from renewable sources. Most of these can be found in the north-east of Germany, for the most part wind turbines. Wind farms are also rising in the Baltic Sea. We connect them to the 50Hertz power grid. To safely and reliably transport the generated electricity to the consumption centres, we are modelling our technical installations and systems to successfully deliver these transmission needs. How it works: overhead lines 3 Transmission system operator in service of society For a successful energy transition 50Hertz operates the transmission grid in the north- Our company east of Germany and we efficiently maintain our grid, expand it to meet the demands and ensure that we At 50Hertz, over 1,100 employees at ten sites ensure maintain the electrical balance between feed-in and that electricity flows around the clock in Berlin, electricity consumption in our grid area. We involve the Brandenburg, Hamburg, Mecklenburg-Western public at an early stage if and when the situation arises Pomerania, Saxony, Saxony-Anhalt, and Thuringia. that we need to extend or upgrade our lines. We supply power to around 18 million people. Our grid is one of the most modern in Europe and has an As a transmission system operator, we provide a electrical circuit length of about 10,200 kilometres, reliable infrastructure that flexibly responds to fluctua- or the distance between Berlin and Rio de Janeiro. tions. To this end, we are in constant exchange with our partners, in Germany and abroad. As part of the We are located in the heart of the continent and European interconnected grid, the 50Hertz transmis- are the central hub between northern, eastern and sion system is directly connected to our neighbouring central Europe. Furthermore, we are the largest countries such as Poland, the Czech Republic, Den- export region worldwide for renewably generated mark and (in the future) Sweden. electricity. We are responsible for the construction and operation of lines to connect wind farms at sea to the power grid onshore. Elia ( 80 % ) KfW ( 20 % ) By openly discussing the challenge of grid develop- ment and offering a reliable infrastructure that 50Hertz flexibly responds to the fluctuations, we ensure a successful energy transition in a sustainable world. The shareholders of 50Hertz are the Belgian system operator Elia (80 %) as well as the KfW banking group (20 %), owned by the Federal Republic and the federat- ed states. As a European transmission system operator, 50Hertz is part of the Elia Group and a member of the European association ENTSO-E. 4 How it works: overhead lines Key Switchgear (most with links to distriution system operators) 30 kV 220 kV Transformation 30/220 kV Transformation 30/50 kV Planned/under construction Other companies 0 perating voltage in kV ine 30 kV ine planned/under construction 30 kV ine 220 kV HVC connection 00 kV HVC/C connection 300/320/525 kV planned/under construction Other companies 30/220 kV HVC/Back-toBack-converter 30/50 kV planned/under construction HVC/converter 00 kV HVC/converter planned/ 300/320/525 kV under construction 50Hertz transmission grid ffshore grid connection 50/220 kV ffshore grid connection 50/220 kV Our grid covers an impressive distance of around 10,000 planned/under construction kilometres across the entire eastern part of Germany with Berlin and Hamburg. On land, electricity is mainly transported System users: ur customers are regional distriution system via overhead lines; however, 50Hertz is operating more and operators as well as power plants, pumped storage plants, wind farms and maor industries connected more underground cables as well. Legally imposed principles to the transmission system. apply when selecting the routes for new lines. This includes Conventional power plant the protection of people, wildlife and the environment. This Pumpedstorage plant means that residential areas must be circumvented as much nterconnectors as possible and that nature conservation areas and landscapes nshore/offshore wind farm are occupied only sparingly. 50Hertz bundles lines with existing nshore wind farm planned/under construction routes (for example with railways, motorways and existing lines) ffshore wind farm planned/under construction whenever this is possible and worthwhile and adjusts them to the landscape by means of an appropriate line layout. 1 New construction mostly along existing route STAT AT DECEME 2018 Sweden 150 How it works: overhead lines 5 Denmark Energinet 150 150 220 chleswigHolstein Rostock Mecklenburg Western Pomerania TenneT Güstrow Hamburg Schwerin TenneT 220 Neubrandenburg 1 1 PE randenburg Lower axony Poland 1 220 erlin 220 Frankfurt (Oder) Potsdam TenneT 110 Magdeburg axony-Anhalt Cottbus Halle Leipzig axony 110 1 Dresden PE Weimar Erfurt Jena TenneT Eisenach Gera 1 Chemnitz Thuringia Hesse Zwickau ČEP TenneT avaria Czech epublic 6 How it works: overhead lines What exactly is electricity? Electric current is the name for the flow of small, negatively charged elementary particles (electrons) in a specific direction. This usually happens within a ‘conductor’ of conductive material. Lightning, however, shows us that power can also flow without a conductor. Power flow is most easily explained using the example of a battery. Current Electrochemical processes in the battery separate the Symbol: I charge: the negatively charged electrons congregate Unit: A (ampere) at the negative pole, while on the other side, the Formula: I = U (voltage) / R (resistance) positive pole, only positively charged electrons are found. The charged particles are attracted to each Bright light bulbs – other if the charge is different and repel each other if many electrons are moving the charge is the same. This creates an electron flow from the negative to the positive pole. The principle on which electric current is based, is the property of the electrons to always strive for a neutral state. There is a large electron flow here The current (I) indicates how many free particles move through a conductor, such as the cable, at the Base metal Noble metal Ion bridge same time, and is measured in ampere (A). (e. g. zinc) (e. g. copper) The more electrons per second flow through the conductor, the stronger the electric current and the brighter the light bulb connected to the electrical circuit. However, the voltage remains the same. Flow with Flow with a an excess of shortage of electrons electrons How it works: overhead lines 7 Electricity needs voltage The electric voltage is the driving force What does electricity look like? allowing free electrons to move and Electricity is invisible, despite the fact that it is often portrayed therefore the precondition for the flow in the form of a yellow lightning bolt. Like the wind, which makes trees sway and drives wind turbines, electricity cannot of electricity. It is measured in volt (V). be seen but is only identifiable through its results. This force is the result of the difference in charges between the positive and negative pole. The special state in which electrical voltage creates mechanical forces on the charge carrier is called the electric field. Electricity flows through the 50Hertz transmission system with high power, mainly at an extra high voltage of 220 to 380 kilovolts. As a result, it is possible to transport large quantities of energy across wide distances. Before this elec- tricity can be brought to the consumer, in other words, our wall sockets, it must be transformed to a lower voltage several times over. Voltage Symbol: U Unit: V (volt) Formula: U = I (current) × R (resistance) 8 How it works: overhead lines Direct current and alternating current – a tense relationship U (direction of electricity) The electric current generated for example by batteries is known as direct current, as its direction does not alter over time. Most electronic home appliances, such t (time) as the radio, computer or LED lights require direct Curve shape for direct current current as their power supply. Because the electricity that comes out of the wall socket is alternating current, these appliances have built-in switched-mode power supplies or transformers that convert the electricity. In the case of alternating current, the positive and U (direction of electricity) negative poles periodically exchange their polarity. The charge carriers therefore alternate in direction. In the German and European electrical grids, this t (time) happens 100 times per second or at 50 hertz (see page 10). Technically speaking, alternating current offers the advantage that it can be transformed between Curve shape for single-phase different voltage levels at ease, for example from extra alternating current high voltage in transmission grids to low voltage in households. U (direction of electricity) 120° 120° 120° U1 U2 U3 t (time) Curve shape for three-phase alternating current (three-phase current) How it works: overhead lines 9 A special form of alternating current flows through power grids: three-phase alternating current (or just three-phase current).