The LV network is likely to experience voltage rise, transformer and cable thermal constraints, exacerbated by the increased uptake of LCTs. This project will determine the extent to which a new concept smart transformer can address LV constraints through active power control and feeder meshing. The project will also consider voltage constraints only and to what extent an existing smart transformer technology can address these. This will involve consideration of two key technologies; an existing Hybrid Intelligent Transformer (HIT) and a novel Active Power Control Transformer (ACT). During phase 1 the extent of each solution’s applicability in relation to the NGED LV network will be assessed. Phase 2 will proceed depending on successful stage gate reviews and will involve detailed power systems analysis on typical LV networks. During phase 2, either the ACT prototype will be developed and tested or the HIT will be tested in relation to active power and/or voltage control capabilities.

Benefits

The solution explored as part of this project, seeks to avoid conventional reinforcement on LV feeders, through load sharing between two or more pairs of LV feeders (one constrained and one unconstrained, or both experiencing constraints at different times of day). There are a number of potential use cases for the active power control transformer integrated into the LV network. These are:

• Existing LV feeder loops from the same substation
• Additional LV feeder loops from the same substation
• Meshed feeders from two adjacent substations
• Combination of a meshed feeder pair and looped feeder pair.

Base Cost

The base cost consists of a new distribution transformer and the reinforcement of an LV feeder, assumed to be 300m length.

• Cost of Conventional transformer (1MVA) - £18,000
• Cost of 300m LV cable reinforcement – 300 * £100 =£30,000

Total base cost would therefore be £48,000. For reinforcement of two LV feeders the base cost increases to £78,000.

Method Cost

The method cost is based on the new active power control HIT and the installation/modification of an automated link box switch.

At this stage it is assumed that the HIT cost will be in the region of £35,000 and the automated link box switching will cost £5,000. WP2 of this project will produce more exact costings for the solution.

Therefore, the method cost is estimated to be £40,000. This would increase to £45,000 for the looping/meshing of two feeder pairs.

Financial Benefit

The net benefit that could be achieved for one secondary substation where the solution would be applicable, is between £8,000 and £38,000 depending on what LV reinforcement would have been required without the solution in place.

As it is estimated that the solution would be applicable on around 24,000 LV feeders the total benefit from utilising the solution would be approximately £193 million out to 2050.

It should be noted that this is a research project to prove the efficacy of the solution and extent of applicability on the network. The detailed CBA will be completed during the project, once initial costs are available.

Through developing a smart transformer that will facilitate load sharing between existing LV feeders, the need for conventional cable reinforcement will be reduced and therefore reduce impact on customers due to fewer street works.

It is also envisaged that due to reducing cable reinforcement with the need to only replace the distribution transformer, the outage for network reinforcement will require less time.