This project is developing a modern two-phase link box for use in a specific, unusually-configured section of our network in Croydon, south London. It will lead to short-term benefits of cost and time savings, and in the long-term will help us run this section of the network efficiently for years to come.
The Croydon area of our London network ran on a DC electricity distribution network until the 1930s. Later, when the section transition to AC to align with network operations in the rest of the UK, we kept the area running as a two-phase system for technical reasons. This means we need to use specialist equipment, including link boxes, to help keep the network running. It is known as the Scott Network, named after the engineer who designed it. It’s a completely unique situation in the whole of the UK.
All the legacy Scott link boxes that we use in the area have come to the end of their service lives and need to be replaced. However, to our knowledge, there’s no suitable two-phase LV link box available on the market today, so we need to create one.
As an aside, due to the increase in DC electronic equipment being connected to the distribution network, such as EVs, batteries and solar PV, there has been an increase in research around whether or not it may be suitable to transition some low voltage networks to DC. Research is ongoing.
We’re developing a new piece of equipment that can be used as a modern like-for-like replacement link box for the Scott network. The project scope is to design, develop, test and trial a modern two-phase link box.
Initially, equipment design will be carried out. Once this is approved, two prototypes will be manufactured and tested. Once the devices pass the testing phase, they will be installed in the Scott Network.
We are developing a double busbar link box that is appropriate for use on a two-phase AC network, as well as a DC network. Learnings around double busbar link box configuration could lead to network reliability improvements for all DNOs.
The use of DC networks is an area of ongoing research and we believe as the Scott Network in the Croydon area started off as one, it is appropriate to develop an enduring solution to replace the legacy Scott link boxes. This will provide us with the ability to run the Croydon LV network at DC at some point in the future or even operate AC and DC systems on the same piece of network, which would be a significant technical achievement.
Traditional three-phase link boxes only have a single busbar. A design with an increased number of busbars will result in greater asset resilience, which will improve network quality of supply.
DC LV networks are being investigated more broadly through a number of other DNO projects such as WPD’s DC Share and SPEN’s LV Engine. The Futurelink project is looking at one specific piece of equipment which will be needed to roll out LV DC networks at scale in future.