Preparing to power down the Advanced Computing Facility

^{Above: external generators are delivered to the ACF.}

On 3 September 2024, the Energy Networks Association (ENA) for the United Kingdom issued a safety notice related to an incident involving the failure of a particular type of High-Voltage (HV) circuit breaker. This initial notification was followed by a further ‘Dangerous incident notification’ in January 2025 indicating a further incident had occurred at another HV facility where the circuit breaker had suffered a catastrophic failure. 

Here at the Advanced Computing Facility (ACF) we identified that we had this type of circuit breaker in two main locations of power distribution of our site. 

Engineering specialist consultants on HV systems recommended that the circuit breakers should be replaced because enhanced maintenance regimes will not mitigate the risk of failure.  

The impact of these failures when they occur are two-fold:  

• Infrastructure housing the breakers can become ‘live’ during the failure and there is a risk of electrical arcing from the equipment to anyone in the vicinity.
• The apparatus cannot be repaired and needs to be replaced.  

ACF power down

For these health and safety reasons, we must have a complete power down of the site while specialist contractors undertake a large programme of work to replace the hardware.  

With an approximate six-month lead time for delivery of the new switchgear, we agreed earlier this year to target two weeks at the end of August to complete the works. 

To minimise the risk of causing issues to any of the services operated by EPCC, they are all being gracefully taken offline and powered down from Wednesday 27 August, with the specific date and time of removal from service dependant on each individual one. 

With the entire site powering down on the evening of Friday 29 August, this will be a critical milestone for this project.  

^{Above: a generator is lowered from the delivery lorry.}

Major generator and switchgear delivery 

In the last few days before the power down there have been significant planning, prerequisite work and deliveries to support the main programme of work on Friday 29 August. 

The external generators, which will run 24/7 and provide temporary power supplies to critical services such as lighting, were delivered on Tuesday 19 August. 

^{Below: switchgear ready to install.}

The switchgear order, which was placed in March 2025, was delivered to the site on Wednesday 20 August.   

This is the critical replacement hardware which will allow the work to proceed. This delivery date, which was explicitly agreed in May 2025 as part of wider planning activities with our main electrical contractors, was chosen as part of a detailed plan to allow them to complete significant non-disruptive work before moving the switchgear into position upon delivery.  

In addition to all the significant pre-planning works to date, the main work for EPCC starts this week, with a clearly defined programme to remove access to services and power down hardware gracefully in accordance with discussions with all service managers and owners. While each service is different, all services will be powered down by 17:00 on Friday 29 August when we hand our site over to our main electrical contractors. 

Return to service

The ACF is due to be handed back to EPCC on Monday 15 September at 09:00, and we will start to return the underpinning infrastructure and services thereafter. 

We will post updates throughout this critical project to give an insight into what it takes to complete large-scale electrical and mechanical infrastructure works. 

^{Below: switchgear in place.}