Learnings

Outcomes

All project deliverables are available on the SILVERSMITH website:

https://www.nationalgrid.co.uk/innovation/projects/solving-intelligent-lv-evaluating-responsive-smart-management-to-increase-total-headroom-silversmith 

The outcomes of the project are as follows:

•  A detailed literature review which documents the state-of-the-art technologies which are being developed by suppliers.
•   A breadth-based Network Study which uses the economic model Transform to estimate the demographic of future network constraints witnessed on the LV network from now up until 2050. Different DFES scenarios consider the impact of the LCT uptake rate on network constraints.
•   A depth-based Network Study using PowerFactory’s PowerFactory software to evaluate three case study networks. After connecting LCTs according to the three DFES scenarios, analysis was performed in study years: 2028, 2033, 2040, and 2050. 
• A report detailing the Functional Requirements expected to be needed by each archetype was produced. This details the range of BAU technologies which would be used today, and also where novel technologies are used in place of BAU approaches, detailing the financial savings which could be possible.
•   A power-flow-based study evaluated each of the novel technologies considered in our project. This study evaluated the relative strengths and weaknesses of the technologies.
•   A comprehensive LV Voltage Control Selection Methodology was produced, which clearly explained the types of technologies that should be considered for addressing network compliance issues in different case studies. It also highlighted the scale of customer flexibility which would be required to defer and avoid BAU reinforcement. 
•  A summary report, that gives an overview of how each technology is applied to our network in the study, and reasons why some of the novel technologies were not selected.   

Lessons Learnt

The demographic of network issues

•  Feeder types dominated by commercial customers are forecast to witness primarily voltage rise constraints. This is due to an uptake of PV.
•   Transformer load-related constraints are consistently the most significant issue across all licence areas. 
•  By 2040, thermal constraints will affect 40% of feeders. 27% Transformer, 13% thermal. This increases to 60% by 2050.
•   The network results showed that the Dense Urban network is more likely to experience breaches in thermal capacity significantly before statutory voltage limits are breached. This may mean that solutions which may become necessary for the Dense Urban network will favour those which can reduce circuit loading, particularly during the winter evening peak periods.
•   In the Urban Network, higher levels of PV generation and longer feeders than the Dense Urban network show that statutory upper voltage limits (+10%) could begin to be breached from 2033. It was also found that thermal loading begins to become overloaded during winter peak from 2033 (Leading the Way) and 2040 (Best View) at which point some intervention would be necessary. For the Urban Network, interventions which reduce the thermal loading during the winter whilst also improving voltage management in the summer will be necessary.
•   For the Rural Network, some customers will experience high voltages breaching the upper statutory voltage limits during peak PV export from 2040 onwards. Although circuit loadings remain well below their 100% rating the total loading on the supply transformer will begin to be exceeded for the highest LCT uptake scenarios (Leading the Way). In some situations, circuit loading remains within thermal limits but in rural networks, voltage issues may begin to occur at different points along the feeder.

State-of-the-art LV Voltage Control devices    

• As part of the literature review, a range of solutions have been considered that have the potential to provide either additional voltage or thermal capacity to the network. These solutions range from retrofit devices, physical network interventions, market solutions (encouraging consumer engagement) and policy solutions.
•   The Literature Review documents the operating parameters of different LV voltage control devices. 
•  Modelling LCT uptake using Distribution Future Energy Scenarios (DFES).   
•  Currently, no commercial heat pump profile exists. Within this project, this limited the insights and results obtained for LV feeders, which had more commercial customers connected.
•   It was recommended that an understanding of commercial heat pump profile(s) should be developed such that the effect of commercial heat pumps can be included in future network modelling

Power flow models      

• During the PowerFactory network modelling, several delays were caused by a lack of model convergence. LV network studies are not currently performed as a business-as-usual activity, as such the electrical diagrams are often incomplete or missing detail. Where information was missing, approximations and assumptions were made, which often caused a lack of convergence until improvements were made incrementally.
•  In future work, it is recommended to err on the side of caution when planning detailed network modelling using LV records. It is also recommended that to improve this process, systematic improvements to the LV records should be made.
•   The networks modelled in the PowerFactory work at the project's outset were limited in their ability to evaluate novel solutions. D1.1 showed that very few issues were expected to arise looking out to 2050. When it came to assessing the functional requirements of the novel options, solutions were limited to improving areas of the network that didn’t experience significant issues. In particular, remote switching/meshing was only possible to be modelled on one area of the urban model. 
• One of the main objectives was to understand how often LCT loads would require certain proactive measures to be taken on the LV network. For instance, we wanted to understand how increased LCT loading and export at different times throughout the day may require multiple interventions throughout the day to manage the voltage. By only investigating three scenarios, we were not able to accurately model the impact of this across the network and understand where this may be needed at scale.  

Performance of Novel LV Voltage Control Devices

• To use a STATCOM successfully, remote monitoring of the network is needed. This is to feed into an algorithm which triggers when the STATCOM needs to be operated. Failing to do so would increase losses and consume capacity. 
•  Ideally, a STATCOM would only resolve voltage issues during the middle of the day when the voltage rise is highest due to PV. At other times of the day, it was found to consume too much of the network's capacity due to the additional reactive power flow. 
•  Harmonic filtering and phase balancing offer benefits which primarily apply to the transformer and the HV network upstream of the connection point.  On the LV network, harmonic currents will still exist as the active injection to cancel the harmonics will only benefit the network upstream of the filter.

Most commonly used technologies     

• The novel solutions most commonly deployed across National Grid’s LV network and therefore offering value over business-as-usual solutions are:

o   Network data monitoring.

o   Active network management (dynamic control of the network by controlling, for example, normally open points).

o   Active transformer cooling.

o   Real-Time Thermal Ratings for HV/LV Transformers.

o   If the ENA140 Consultation which is considering whether to widen voltage tolerances is passed, manual tapping to increase headroom could be accommodated on networks where previously it would not be deployable due to voltages dropping below the statutory voltage minimum limit. 

Sensitivity studies       

• Similar solutions are selected to be deployed across all four of National Grid’s electricity distribution licence areas. The proportion of solution deployment is sensitive to the LCT uptake rates on each licence’s area feeder set. Any solutions deployed should be based on the network constraint type and extent of constraint witnessed on the specific feeder. 
•  The number and types of distinct solutions required across National’s Grid network are independent of the scenario. Regardless of the actual LCT uptake rate, the distinct solutions will be utilised for particular feeders due to the variability in the clustering of LCT deployments. Network Operators do not need to be concerned about the uptake rate of LCT across the system, instead, they should focus on the constraint type and extent caused by LCTs on each feeder. 

Consideration of flexibility

•   The use of domestic flexibility (technology agnostic) was considered as part of the Selection Methodology. The average amount of flexibility per feeder and per customer on that feeder was calculated to i) defer the initial reinforcement by 5 years, and ii) remove the need for the second wave of reinforcement. Based on these studies, to defer network reinforcement for 5 years from the time of the first network constraint, between 0.7kW and 2.1kW per customer are required depending upon the network archetype. 
•  As further trials investigating domestic flexibility are conducted, more accurate information will be available to estimate the amount of demand side response available to shift demand away from peak times, and the expected cost which DSOs would be willing to pay.

Opportunity for future innovation       

•  It was estimated that solutions offering cable headroom increase between 15% and 100%, for less than £50,000, would have significant value. Where a network experiences a cable headroom requirement of between 15% and 50% headroom uplift, Transform would pick network meshing. However, for practical reasons, it is unlikely that retrofitting Network Meshing would be achievable at scale which leaves a significant opportunity. In cases where network meshing is not possible, the next logical solution is splitting the feeder at a totex cost of £53,880. Therefore solutions that can release greater than 15% thermal cable capacity with less cost and technical challenge than that of permanent network meshing would offer significant value. 
•  Innovative technologies that could offer between 20% and 80% thermal transformer capacity at less than approximately £16,000 per feeder (for feeders supplied by Ground Mounted Transformers (GMTs)) or £7,500 per feeder (for feeders supplied by Pole Mounted Transformers (PMTs)) would provide significant value to the network operator. Innovation activity could investigate solutions able to fill this gap.
•   The available solution set has a gap between cheaper minor improvements and costly major improvements. Where solutions offering minor improvements don’t address the network issues, we are forced to deploy far more costly solutions. Intermediate solutions would offer significant savings.

Recommended technology trials

•  Of the available technologies, active transformer cooling was widely selected and recommended for a trial by the late 2020s.
•   By the early 2030s, trial Real-Time Thermal Ratings (RTTR) for HV/LV Transformers across a sample of National Grid’s pole-mounted transformers are forecast to become thermally constrained. Trials should focus on how to install equipment necessary for RTTR on PMTs and on quantifying the benefit of RTTR on thermal PMT capacity.
•   By the mid-2030s trial active network management across a section of National Grid’s LV network and quantify the thermal and voltage headroom release achieved.
•   Continue to innovate applications and algorithms deployable to LV monitoring equipment to expand the benefits from the monitoring equipment and to maximise utilisation of existing assets.