Mini-series: “The war of currents” – the beginnings of the alternating voltage

We are writing the year 1905. It is night and we wander in our minds through the illuminated streets of any western city. Passing industrial plants with steaming chimneys, where the machines rattle and the workers toil even at late hours. The industrial revolution is just over but the economy is still running at full speed. Labour protection laws and a ban on child labour were not to be introduced until much later.

Once at home, the first step is to go to the light switch and the whole house is lit up. This has now become standard in many urban households.

The invention of the transformer in 1881 made it possible to transport large amounts of energy over long distances at low cost. This is because transformers can transmit a required effective electrical power by means of a higher voltage with a lower current and thus with lower line losses and transform it back into lower voltages at the consumer. This development in electrification was supplemented in 1887 with the invention of two-phase alternating current and three-phase alternating current only one year later, and forms the two- or three-phase systems that are common today in electrical power engineering and in power grids.

But the road to this was long and steep. Around 1890, the so-called war of currents broke out between the representatives of direct current, led by Thomas Alva Edison (1847-1931), and the representatives of alternating current, with George Westinghouse (1846-1914) at the helm. Edison had already secured various patents and signed binding contracts with hotels, industrial plants and other large companies some time ago, which made it extremely difficult for Westinghouse to gain a foothold in the limited market.

However, Westinghouse’s alternating voltage allowed much higher voltages and thus more energy and better performance and had several advantages over direct current voltage but it also came into disrepute for being particularly dangerous and even deadly. This reputation was publicly fueled by Edison and the representatives of direct voltage, who saw their chance and wanted to stop the spread of alternating voltage in order not to lose their market leadership. The public debate ended one year later in favour of alternating current voltage because of its technological advantages. Even today, in the 21st century, alternating voltage is still used almost exclusively. However, even today, direct and alternating current networks still exist side by side. The most famous German example of a direct voltage network is the NordLink. This is also known as the “green cable” between Germany and Norway and is the first direct electricity connection between the two countries. The high-voltage direct-current link will enable the exchange of 1,400 megawatts of renewable energy – wind power from Germany and hydroelectric power from Norway – and will thus make a noticeable contribution to the German CO2 balance. Edison would have been delighted!