Power Up?

By Tjeerd Burger, young professional – Take a look at this simple map, just taken from Wikepedia, and imagine what could explain the difference in color between the different European countries. And yes, it has to do with infrastructure.

electrification railways eu

The map represents the different railway electrification systems used in Europe:

750 V DC

1,5 kV  DC

3 kV DC

15 kV, 16,7 Hz AC

25 kV, 50 Hz AC


An interesting but somewhat underexposed topic which deserves some attention considering the current discussion in the Netherlands whether to upgrade its system to 3kV. To start, we take a quick look at the history of railway electrification. Electrification of railway lines generally took place in the first half of the 20th century and for various reasons a type of system was chosen in each country. For example, in 1908 the first part of the Dutch railway system between Rotterdam and The Hague was electrified, 10kV (AC) at that time. Later, in 1924, the second line was electrified with a 1,5kV DC system, which became the standard system in the Netherlands. Looking at Europe in general, the 15kV and 25kV AC systems are currently the most widely used systems.

However, over a century little has changed apparently in this field of infrastructure. Knowledge about electrical transmission systems has grown significantly and has improved the systems, but it has not led to standardization or the introduction of new systems. Surprisingly, also international cooperation through the European Union has not led to standardization. Several directives aim to stimulate interoperability but they do not steer towards a specific system. On the other hand, these directives do aim to create a standard interlocking system, the European Rail Traffic Management System (ERTMS). Choosing a specific system is probably too cumbersome and only works if all countries adapt the chosen system. Moreover, the costs for such change will by far outweigh the potential benefits, despite the higher costs for special, multi-tolerable locomotives and timely locomotive changes at border stations. Changes in electrification systems initiated by the E.U. are therefore not likely, but this may be different on a national level.

Of the European countries the Netherlands has one of the lowest voltage levels. On the other hand, it also has one of the busiest networks. An illogical combination. For example, a high number of feeding stations are necessary to ensure enough network capacity. As the Dutch Railways are currently trying to increase the frequency of train services a higher voltage level seems to be logical step. Also, more power means quicker acceleration and thus increasing capacity. A higher voltage level also leads to a significant energy reduction. All very obvious reasons for an upgrade, so why has the Dutch Railway operator not changed its network?

Well, to be true, there are also some significant con’s. First of all, although knowledge about electrical systems has grown over the past centuries, there is still not a clear optimum system. The 25kV AC systems are currently to be believed as the most optimum choice, but that is not without doubt. For example, there is the never-ending discussion about AC/DC. It is easier to transform AC but DC has a lower loss of energy over greater distances. Considering the current (consumer) electrical devices, these are mostly based upon DC. It’s not unthinkable we might shift to the DC-side of the story in the coming decades. Nonetheless, the most recent built lines in the Netherlands are equipped with the 25kV AC systems. Especially as these lines are a dedicated high-speed and cargo line it has clear benefits for the international trains. On the other hand, while high-speed trains demand higher voltage levels, cargo trains don’t necessarily do and equipping the Betuwe-line with 25kV AC was a political choice rather than a technical one.

However, transforming an existing system into another is a whole different story. To begin with, the higher voltage level heightens the risk of electrostatic discharge on nearby structures. Numerous fly-overs, tunnels and stations therefore need to be adjusted to ensure a safe transition. Furthermore, all trains need to be adapted to the new systems. The newest carriages on the network are already multi–tolerable, but all the other trains need to be adjusted or replaced. Who’s going to pay these costs? Another interesting questions is how you are going to exert the change. Is the new network built parallel to the existing system, or is the network replaced line-by-line, with significant nuisance for passengers? Looking at the Netherlands, the proposed upgrade to 3kV has the big advantage that the existing infrastructure can largely facilitate a 3kV system. But even then, due to limited availability of specialized engineers a change has to be executed in phases.

Different challenges are faced when dealing with non-electrified lines. Despite the advantages of replacing polluting diesel-powered locomotives, financing, building and maintaining a complete electrification system is a real challenge, especially for undeveloped countries. Lessons can be learned from India, which is using PPP- constructions to electrify it’s lines, financed by the yearly saved fuel costs. There are other, promising alternatives. In 2015 the first battery powered train was introduced in the UK and in France trams are powered by induction. But since laying wires above the ground is still less expensive than putting them underground these techniques will only remain ‘promising’ for now. And although electrification can attractive for financial reasons, it comes with an important remark. The ongoing global electronic shift can only fulfill its potential when renewable energy is used. Building new coal power plants to meet a raised energy demand can wipe away all the potential benefits of the electronic shift.

It will be interesting to see how the discussion ends in the Netherlands, both from a political and technical perspective, and whether they dare to change their system after almost a decade. Hopefully my remarks have given some background to this rather technical issue and has it shed some light on this type of underexposed infrastructure.