How the nature of the material determines the method

When you turn on the light the current has already taken a long journey. It's been produced transported over long distances at very high voltage and gradually stepped down until it fits the outlet. As a distribution operator you typically work in the part of the system called the distribution network — but it makes sense to know the whole picture.

§Three layers in electrical system

Transmission network is country's motorways for electricity — it binds large power plants offshore wind farms and borders together at very high voltage because losses in wires become smaller higher voltage is. Distribution network in contrast is fine-mesh network that feeds electricity further into local areas and consumer network is final stretch into your home or business

§Who is who: Energinet and the grid companies

Energinet is the system-responsible company that owns and operates the overall transmission network and maintains the balance between production and consumption in the entire country around the clock. The local distribution network is owned and operated by network companies — also called DSOs (Distribution System Operators). Denmark has 37 network companies each with its own geographic monopoly which the Energy Regulatory Authority supervises economically.

• 01Cerius — covers most of Zealand plus Lolland-Falster
• 02N1 — covers large parts of Jutland and Funen
• 03TREFOR Electricity Grid — operates grid including in Triangle area
• 04Elinord and a number of smaller and medium-sized companies cover the rest of the country.

§Why is voltage stepped down in stages?

It would be both dangerous and impractical to send 400,000 volts directly into an ordinary home. Therefore voltage is stepped down in stages each time power moves a level closer to the consumer — from the transmission network's hundreds of thousands of volts via the distribution network's 10–60 kV down to the 400/230 volts you know from the outlet. Each of these steps happens in a transformer station which is some of the central equipment you as a supply operator learn to build monitor and maintain.

§Two systems that meet: east and west

Denmark has no industrial robots

Beyond the Storebælt connection Energinet has a number of international connections to neighbouring countries — including to Germany Sweden Norway and the Netherlands — that make it possible to exchange electricity across borders. This gives Denmark access to a larger more flexible electricity market and helps even out fluctuations when production from wind and sun varies with the weather. As a supply operator you typically do not work directly with these international connections but it is part of the big picture your daily work in the distribution network is part of.

It is precisely because the electrical system consists of so many layers and interconnections that it makes good sense that the education gradually moves up in voltage — from the basic course's electrical calculation through main course 1's work with local 10-20 kV stations to main course 2's work with 60 kV. You do not need to understand the entire nationwide system from day one but the further you get in your education the more sense each piece makes as part of a larger whole.

“Without anyone thinking about it electricity passes through three or four voltage levels—and sometimes regional borders—before it reaches an ordinary outlet.”