What do we currently expect and what do we currently get?

The resilience of the power networks in the UK is generally very good unless you are supplied by an overhead line susceptible to extreme weather conditions or live in a remote part of the country or down the end of a lane with no chance of a second back up supply. There are a number of places which are known to be what is termed “worst served”.

Back in the 1990’s the newly privatised regulated Distribution Network Operators were denounced for both general poor network performance both on the duration of breaks in service and the frequency of events. The penalties they faced forced a big push to improve analysis of events, apply critical thinking and how to use technology to restore supplies more quickly, and how to design or modify networks to reduce any impact to the maximum number of affected customers quickest.

We now have a highly automated high voltage network which is close to being able to automatically switch loads to healthy circuits and keep customers with power quickly with very little human intervention or at least have engineers observe and check what the automation proposes.

From a resilience perspective and with the pressure on overhead lines not being the favoured, mostly for aesthetic reasons, most new network is installed underground in public highways where the biggest impact is someone else working in the road or construction damages a cable. There is an inevitability that the +60-year-old cables will start to fail but have not materialised just yet.

Availability is subtly different, as power capacity is naturally constrained by how much capacity is accessible and what load exists at any one time. Load customers have historically enjoyed having a known fixed capacity that they can call upon with very little constraint.

The electricity network circuits and transformers have historically been developed to provide power from a National Grid of very large power stations and distributed across the UK. This is changing due to the growth of renewables which are disparate and smaller in size giving rise to other issues on capacity with generation export competing at times with load to use the circuits. The DNOs are having to evolve into System Operators (SO) where they have to manage a dynamic situation in real time.

How Are DataCentres Affected?

In network history terms most DCs have been connected in very recent times. Owner/Operators have in the main been very diligent in analysing and risk assessing their grid connection. As a matter of course, most DCs will have the standard N+1 grid connection (or better), and will be acutely aware that this means no loss of supply for a single fault. Beyond this there is a level of generation back up. The Distribution Network Operators (DNOs) under their licence have to offer this level of service under the security of supply standards.

It is not the case that resilience receives the same level of scrutiny and many Owner/Operators would not know how to approach a review of how resilient their supply was beyond the point of connection.