The manager of the high-voltage grid, Tennet, did not expect the failure of two connections last night in Amsterdam-Zuidoost to lead to a disruption of the check-in system at Schiphol. But Tennet does not rule out the possibility that the failure in Southeast also caused a voltage dip at Schiphol.

Schiphol suspects that it did. That would mean that the airport temporarily had less power. As a result, it immediately switched to emergency power. "But it takes time before everything is fully operational again," writes a spokesperson.

Dips inevitable

Professor Han Slootweg of Eindhoven University of Technology does not think a voltage dip is an obvious explanation. "Dips in the mains voltage are inevitable. They also occur very regularly. It is therefore important to design critical systems in such a way that a voltage dip has as little impact as possible." Schiphol has so-called UPS to cope with the temporary interruption of the power supply and prevent the failure of business-critical systems/processes. Tennet was therefore surprised after the outage at Schiphol.

Unfortunately, it is now starting to look woefully familiar: Amsterdam and power cuts. The city's image is therefore not helped by the fact that last night another failure had to be lamented. This time, 38,000 connections in Amsterdam Zuidoost were affected, but the systems at part of Schiphol Airport also went black after a brief dip in voltage.

According to Tennet, at 00:42 last night something went wrong in one of the two 150 kV circuits connecting Bijlmer Zuid to Venserweg and Amstelveen. The circuits in question are constructed entirely as ground cables, and given the time of day when the failure occurred, it seems unlikely that digging damage in one of the circuits was the cause. At least not in the immediate sense, although of course something may have been damaged longer ago. "We need to check whether the problems at Schiphol are really the result of that voltage dip. And whether this is something they need to guard against themselves or whether it is down to TenneT," explained the Tennet spokeswoman.

It is also possible that something went wrong at Bijlmer Zuid transformer substation itself. Information about this is lacking at HoogspanningsNet.nl. However, the disruption at Bijlmer Noord or Amstelveen did cause such a pendulum (voltage wave) through Liander's underlying 50 kV grid that the 50 kV station Schiphol Oost also fell off the electricity grid, or at least caused such a voltage dip that the systems briefly failed. As a result, the effect affected the electrical power supplies of critical systems at Schiphol and consequently delayed check-in for the rest of the day.

According to Liander, only 18,000 connections in Amsterdam were left without power. But Liander reported on its website that all problems were over only after 10.30am. In any case, the cause was not at Liander. How the disruption in Tennet's transmission grid could have caused the 50 kV sub-grid in Amstelveen to experience such a dip that stations went down is currently still under investigation.

Schiphol is investigating what went wrong in the check-in systems as a result of the major power failure in Amsterdam. As a result, many dozens of flights were delayed or cancelled. As soon as the power went out, the emergency generator was immediately activated. Only, after that, it takes some time for all systems to restart. These are quite complex it-systems," a Schiphol spokesman explained the breakdown in the check-in systems. There will be an independent investigation into the cause. An internal investigation into the incident will also be launched. Who will do the external investigation is not yet known. ''We are looking for a good, reputable party,'' a spokesperson informed. Schiphol regrets that so many travellers were seriously inconvenienced. ''We therefore want to know exactly how this situation could have happened.''

Air traffic control did switch to UPS / emergency power immediately after the major power failure As a result, no radar screens failed anywhere and safety was not compromised, he stressed. "The consequences were only major for departing and arriving flights."

UPS = Uninterruptible Power System On 27 September 2018cis planned a Power Quality Masterclass organised by the KIVI Department of Electrical Engineering in collaboration with HyTeps Specialist in Power Quality and Energy Efficency

On 10 June 2018, Herman Stil wrote the following article in the Parool

Spot on spot at fault

Schiphol: Evaluation power hiccup May holiday

Schiphol is not well prepared for a disaster or other crisis. The major power cut at the end of April involved waiting too long before taking action. 'The question is whether the crisis response plan is adequate.'