TenneT did not comply with statutory requirements in Diemen power outage

Dutch transmission system operator (TSO) TenneT failed to comply with its statutory requirements in the power outage that occurred in the high voltage power station in Diemen (near Amsterdam) in March 2015. This has been determined by the Netherlands Authority for Consumers and Markets (ACM) in a dispute that international steel producer Tata Steel had filed with ACM.

Technical cause of the outage

Following the dispute filed by Tata Steel, ACM launched a new, wider investigation into the power outage in TenneT’s 380kV network. A previous investigation had revealed that the outage was caused by a combination of a technical failure and a human error. That investigation was conducted by an external consultancy commissioned by TenneT, under the watchful eye of ACM.

The aim of the first investigation was primarily to establish the technical cause of the outage, and to draw lessons from it.

Obtaining the information to settle the dispute

In the newer, wider investigation, ACM also looked at the “N-1”- criterion. This statutory criterion means that an outage in one part of the grid, for example in a circuit or in a transformer, cannot lead to an interruption in the transmission of electricity. TenneT has violated this standard through the way in which the Diemen power station was designed.

The aim of the second investigation, which has been conducted by ACM, was to obtain the necessary information to be able to settle the dispute between Tata Steel and TenneT.

A million households were left without power

Due to the power outage of 27 March, 2015, approximately 1 million households in the Dutch province of North-Holland and the adjacent province of Flevoland were left without power for one hour. Rail traffic and air traffic were disrupted, hospitals had to cancel operations, and telephone systems broke down.

Efficient system operation

ACM supports the objective of realizing an affordable, secure, and sustainable supply of energy. It regulates system operators that have a monopoly on the transmission of natural gas and electricity. ACM’s regulatory regime ensures that tariffs are not higher than necessary, and it helps create a healthy investment climate.