New power supply tested at Zuid station

The GRGVI is a key component of the system that powers the metro. Every second, grid operator Liander supplies the rectifier station with electricity at a voltage of 10,000 Volt (V). (By way of comparison: a battery has a voltage of 1.2 V, a high-voltage cable as much as 380,000 V.) This voltage is distributed across five groups, each with a fail-safe mechanism that deactivates the group in emergencies – just like a domestic circuit breaker. A transformer then converts two of the groups into 610 V, to enable the rectifier to convert the 610 V alternating current into the 750 V direct current that powers the metros (see box) – in a process referred to as rectification.

The direct current distribution system then sends the 750 V direct current via switchgear to a cable next to the rails. Known as the ‘third rail’, this supplies the metro with the energy it needs. So, while the name ‘rectifier direct current distribution system’ may be quite a mouthful, it is an apt choice of words.

The GRGVI is a large blue cabinet with 11 doors and is not visible from outside the windowless building in Parnassusweg. It was extensively tested in the factory in Hungary. Why not here in Zuidas? Karel: ‘Of course, we’re also doing that. But testing on location means that all of the experts are on hand if something needs adjusting. Besides that, the direct contact also prevents any misunderstandings – all of which amount to failure costs in the form of (travelling) time that can be saved by going to the actual factory.’

‘We’re testing four things’, explains Karel. ‘It needs to work, it needs to match our design (of the construction consortium, Ed.), it has to meet the requirements of the commissioning authority Zuidasdok, and, finally, it obviously has to be safe.’ Beforehand, the manufacturer shared its own test results and we then checked these in Hungary with experts from the GVB (the Amsterdam local transport company). ‘There were more than a hundred findings, which is quite normal for this kind of project’, explains Karel. ‘Usually, around 80% are cosmetic, such as a display that’s set in English – hardly ideal for Dutch maintenance workers.’

After the on-location test, the whole system was moved to Parnassusweg. ‘Then we test whether everything has been properly assembled and whether all of the settings are correct’, says Karel. ‘This includes such aspects as the threshold values that the GVB applies to the monitoring system: if certain figures are higher or lower than these values, a safety protocol kicks in. It’s a bespoke solution.’ Each component of the system is then tested by means of simulations. Finally, according to Karel, there is an overall test in Parnassusweg once all of the systems have been connected up to each other. This kind of extensive testing process can sometimes result in fatal findings, when the product fails to work for some reason or does not work safely. Karel laughs: ‘Fortunately, there were none of those this time.’