Chapter 2:

Seeds of change

Electricity North West (ENW) has been acknowledged, even by other distribution networks, as leading the charge on voltage management.

Back in 2012, ENW launched its somewhat controversial CLASS (Customer Load Active System Services) trial. The initial aim of the project was to demonstrate that dynamic voltage control could be used to provide demand-side response, both to deal with network constraints at peak times and to provide balancing services to what was then the Electricity System Operator (ESO), including frequency response.

The project saw the company install autonomous substation controllers (ASCs) at 60 of its primary substations to link its control room systems to the automatic voltage control relays it already used to operate the transformers’ tap changers.

The controversy stemmed from concerns that the provision of balancing services by distribution network operators (DNOs) would create real or perceived conflicts of interest and could undermine the development of competing sources of flexibility.

Despite these concerns, Ofgem decided in December 2022 to continue allowing ENW and other DNOs to provide this type of service to the ESO as a directly remunerated service.

Following the success of the trial, which concluded in 2015, the company publicly announced the rollout of ASCs to another 260 substations. This number has increased further still since the company began incorporating the technology into its business-as-usual installation or replacement of new and existing primary substations.

ENW followed up CLASS with its Smart Street trial in which it installed voltage control technology at six primary and 38 secondary substations to enable it to optimise the voltage levels on its low voltage network. This included the installation of on-load tap changers at five secondary substations.

The tap position of transformers determines the ratio of coils on either side and therefore the step down in voltage. In contrast to primary substations, most secondary substations have off-load tap changers meaning they have to be de-energised to change the tap position. In practice, this very rarely happens. Normally, engineers just ‘set and forget’.

The installation of on-load tap changers with more tap positions – nine rather than the usual five – allowed ENW to exercise more direct and precise control over voltages on the low voltage network, rather than doing so indirectly and imprecisely from higher up the network.

The underlying aim of the project, which concluded in 2018, was to enable ENW to run the low voltage network at lower voltages, thereby reducing energy demand and saving consumers money on their bills.

This is also the stated aim of Northern Powergrid’s ongoing Boston Spa Energy Efficiency Trial (BEET). In contrast to Smart Street, BEET does not involve the rollout of on-load tap changers to secondary substations, instead looking to make smarter use of those already in place at primary substations.

Mark Callum from Northern Powergrid says smart meters are a key enabler for this: “We've got something like 60% rollout now of smart meters in our patch and these things can actually record voltage data and send it back. They weren't originally intended for that. But we know these things do record voltage. We know that they're about ±1% accurate.”

He says they have gone from “this old world of not really knowing what was happening on our low voltage networks” to having “millions of smart meters that can give us voltage data. That's game changing”.

Callum says this data is fed into what the company has dubbed a “BEETbox”, which analyses the information and works out what tap positions should be set at their primary substations. The effects of any actions they take can then be measured through the smart meters and reported back into the BEETbox, creating a constant feedback loop that cycles every half hour.

He says Northern Powergrid was already able to control voltages at its primary substations from its network management system as a result of £83 million of smart grid investments undertaken during the ED1 period: “The cool thing with BEET is we can ramp it up and scale it for thousands of customers really quickly. We're in the middle of the trial now, but we've got really aggressive plans to roll this out, essentially tackling 10% of the network a year once we start.”

Callum says this equates to "hundreds of thousands of customers a year" and that Northern Powergrid put £7 million into its business plan to start the rollout.

“Smart Street's definitely got its place, but unfortunately, it's very asset heavy, very intensive. You can't scale it up quickly”, he says.

He believes their BEET system “can probably get 80% of the benefit of something like Smart Street but only spend less than 20% per customer”.