New power lines for the transformation of the energy system
Klaus-Dieter Maubach explains the fundamental difference between integrated grids and transmission grids
Prof. Dr. Klaus Dieter Maubach
Former Member of the Board of Management of E.ON SE (03/31/2013)
The term "integrated grid" occurs repeatedly in the ongoing debate about the expansion of the German extra-high-voltage grids. In general, the term is used in its correct sense by representatives of the power industry but, by contrast, many others like to call these transmission grids. Is the difference only minimal? No - there is a fundamental difference as regards the capacity of the grids.
A brief look at the history of German power supply clearly shows what we still have to keep in mind today. Public power supply more than 100 years ago was a fairly local matter all over the world. Power supply islands were formed, generally in cities. Only much later, with the construction of overhead power lines which were rated for higher voltage levels, these islands were connected to one another across regions. Such an "(inter)connection" initially served to create a solidarity community. The islands thus connected to one another were able to help each other in the event of a power station failure in one of the two islands. Everyone benefited from this. This was the start of integrated grids.
This philosophy continued. It was extended across national borders. "Deutsche Verbundgesellschaft" (DVG), established in 1948, was an alliance of all German integrated grid operators. This integrated grid was also expanded throughout Europe. The principle worked exceptionally well. The efficiency of this cross-border cooperation proved its worth time and again especially for providing reserve capacity and in the event of a failure – so it is no wonder that the community of integrated grids has continued to grow steadily and today interconnects almost all of continental Europe.
Nowadays, the requirements placed on our grids are much higher. They are perhaps best compared with the situation in Sweden, where there were and still are actual power transmission grids. While hydroelectric power is generated in the north of Sweden, the consumption centres are in the south of the country. Power transmission lines running from north to south bring the electricity generated by hydroelectric power to the south. It is logical that such power transmission grids have to have completely different transmission capacities than the integrated grids which exist in continental Europe. To use a metaphor: the grids in Sweden are more like six-lane motorways whereas we in Germany only have main roads.
With the huge expansion of wind power in Germany, the development of actual transmission grids is now on the agenda for us - with the same consequences for capacity expansion as in Sweden. In this respect, the grid development plan recently submitted by the four transmission grid operators to the Federal Network Agency signifies an historic turning point. For the first time, extremely high-capacity power transmission lines running from north to south are being proposed in Germany. And that will just be the beginning.
Incidentally, the power transmission lines in Sweden, and also in all other countries in the world, are being developed almost without exception as overhead lines. To remain with our metaphor: no country in the world has so far had the idea of running its six-lane motorways underground over large distances. It remains to be seen whether we come to realize this, too. We could learn from others in this respect …