Learnings

Outcomes

2023/2024 

Various scenarios have been agreed for inclusion in the next stage of the system study to investigate the potential benefits and future deployment opportunity of SmartValve in the network. These scenarios include boundary flow under normal intact conditions and critical contingencies without any SmartValve, boundary flow with a single SmartValve participating, and boundary flow with the synergistic operation of multiple SmartValves. Please note that the project is at a very early stage and more outcomes of the project will be shared in the next progress report. 

2024/2025 

Studies show clear benefits of wide-area coordinated control of Static Synchronous Series Compensator (SSSCs) (i.e. SmartValves) in optimising power flow across the network, maximising boundary capability compared to single-location operation. · Traditionally, SSSCs have been used to push power off heavily loaded circuits. However, using a combination of pushing power off overloaded lines and pulling power onto underutilised lines is significantly more effective. The studies also suggest that pre-fault operation could provide additional benefits in terms of optimising power flow and enhancing boundary capability. 

A Python-based wide-area coordinated control planning tool has been developed and validated. It will be integrated with DIgSILENT PowerFactory to automate the studies of transmission network planning and control, with a particular focus on the deployment of SSSCs. Studies indicate that SSSCs installed on the B8 boundary have the potential to also provide significant capacity improvements for the B7 and B9 boundaries. Few locations and corresponding siting points for future deployment of SSSCs have been identified and recommended to consider in network planning. However, it is important to note that the recommendations are based on results from the study, which did not consider any post-fault actions involving QBs. Additional studies incorporating various scenarios with QBs in operation will need to be conducted to make a thorough recommendation. 

Recommendations for further work
None to report at this stage. 

Lessons Learnt

2024/2025 

The network studies were conducted using a reduced network model for B7a, B8, and B9, which limits the accuracy of the study. It is recommended that a larger area network model or a complete GB network model be used to enable a more comprehensive system study.

2025/2026

• Voltage compliance binds before thermal capacity at high boundary flows. Across boundaries B7a, B8 and B9, as the boundary target was incrementally raised, voltage limits were reached well before the worst thermal overload occurred.
• The limiting contingency changes with boundary flow. A contingency that is benign at the operational flow level can become the binding case once the boundary is pushed by 1–2 GW. Single-snapshot studies do not capture that a SmartValve deployment optimal for today's limiting case may be the wrong choice for a future scenario. Incremental boundary-flow stepping (rather than a single design-flow snapshot) is required to capture the true headroom and to identify which contingency truly bounds the boundary in each operating regime.
• QBs and SmartValves are complementary, not redundant. Studies confirm that combining QB tap optimisation with SmartValve voltage injection unlocks boundary capacity that neither device achieves on its own. QBs reshape the real-power split between parallel paths, while SmartValves fine-tune the loading distribution at branch level. Treating either technology in isolation underestimates available capacity or risks a sub-optimal investment recommendation.
• Some N-1 contingencies are infeasible under a finite future-SmartValve budget. When the planner caps the deployment , the optimiser will, on occasion, correctly identify a contingency it cannot clear within that budget. The constraint is the available device count as opposed to a tool failure. With an effectively unlimited SmartValve budget the tool can drive boundary utilisation close to 100% of the thermal envelope on virtually every contingency, provided the network does not hit a voltage-collapse limit first. The infeasibility result is therefore a planning signal to either raise the SmartValve budget if the cost/benefit supports it, or accept that the boundary target requires investment beyond power-flow control,  network reinforcement, demand-side flexibility, or additional reactive plant to keep voltages within limits at high flows.
• Wide-area effects extend the 2024/2025 reduced-network-model lesson. Even within the reduced B7a/B8 footprints, future SmartValve candidates close to the model boundary showed sensitivity-matrix entries that were difficult to validate against the full-system response. Until a larger-area or full-GB model is used, the siting recommendations should be treated as indicative and re-verified before any procurement decision is made.
   

Dissemination 

2025/2026

• The wide-area coordinated control planning tool is now a deployable application with a configurable settings interface, allowing planners to vary boundaries, voltage limits, search strategy, future-SmartValve budget and inclusion of MSC/SVC/QB devices without touching Grid Code.
• The tool produces auditable artefacts for each run including per-contingency results CSVs, combined-optimisation summary JSON, all-PFC setpoint heatmaps, rated-current and operating-current tables, and a self-contained HTML dashboard bundle that NGET planners can share with stakeholders.
• Network studies on boundaries B7a / B8 confirm that wide-area coordinated optimisation of multiple SmartValves achieves materially higher boundary capacity than single-location dispatch, and that combining SmartValve dispatch with QB tap optimisation extracts additional capacity without requiring new physical assets.
• The combined optimisation framework correctly identifies the limiting contingency (and the specific lines responsible for persistent overload) when no feasible joint solution exists at a given boundary-flow target, giving planners a clear signal of where the network is constrained.