The SmartValves by National Grid - flexible power flows for UK grids

SmartValves by National Grid sit inside a humming substation, their cabinets warm to the touch as cooling fans push out a steady stream of air and the smell of metal and transformer oil hangs in the room. These devices quietly reshape how electricity flows through the UK high-voltage network. Engineers like Craig Dyke, Head of National Control, walk past rows of equipment that now include SmartValve units as standard tools for balancing the grid.

How SmartValves work on the grid

SmartValves are modular power flow control devices installed on existing transmission lines to actively redirect electricity and relieve overloaded circuits. Each unit uses power electronics and real-time control algorithms to increase or decrease the effective impedance of a line, steering power towards underused routes. In practice, this lets National Grid push more renewable generation through its existing steel towers and conductors without waiting years for new lines to be built.

The technology originates from Smart Wires Inc., whose SmartValve product has been rolled out in several National Grid projects in England and Wales since the early 2020s. National Grid deploys clusters of these valves at substations, typically in containerised or cabinet formats, with each installation adding tens to hundreds of megawatts of controllable transfer capacity. According to project documentation, SmartValve deployments can unlock up to 1-2 GW of additional capacity across a region by re-routing flows and reducing constraints.

Why National Grid uses SmartValves

National Grid’s transmission planning teams face a simple physical problem: some 400 kV corridors are congested while parallel paths remain underused. SmartValves help solve this by sensing line loading and adjusting their settings within seconds to keep equipment within thermal and stability limits. The devices effectively increase usable capacity on selected paths, making better use of existing assets and deferring costly reinforcement projects.

In several public case studies, National Grid has highlighted SmartValve projects where constraint costs on specific routes fell significantly after installation because power could be redirected away from overloaded circuits. For consumers, this matters because constraint payments to generators and redispatch costs feed into final electricity prices. By reducing these payments, SmartValves can support lower system operation costs while still accommodating more wind or solar generation when weather conditions suddenly change.

Placement in UK substations

SmartValves are usually installed at substations where multiple lines converge, such as key nodes in Scotland-England interconnection corridors or major load centers. Technicians bolt the equipment onto concrete pads and connect it via high-voltage bushings and control wiring to existing busbars and lines. Inside the substation, the cabinets hum next to conventional transformers and breakers, adding a new layer of digital control to hardware that often dates back decades.

National Grid has indicated that SmartValve deployments are selected after power flow studies identify which lines would benefit most from dynamic impedance control. The product’s modular nature means the operator can add or remove units as network needs evolve. In some projects, SmartValves are combined with other technologies like series compensation or phase-shifting transformers, creating a toolkit of options for directing power flows over long distances.

Role in renewable integration

One of the key reasons National Grid invests in SmartValves is the rapid build-out of offshore wind in the North Sea and onshore renewables across the UK. These generation clusters can overload certain transmission corridors during windy periods while other routes remain underutilized. SmartValves help keep that power moving by easing bottlenecks without waiting for new overhead lines or underground cables, which often face lengthy planning processes.

Craig Dyke and his colleagues in the National Control Centre have described how flexible tools like SmartValves support real-time balancing when renewables surge or dip unexpectedly. Instead of relying only on redispatching generators, they can now manipulate the network itself, shifting flows to lines that have spare headroom. This reduces the need to curtail low-carbon generation and supports the UK’s decarbonization targets by letting more green electricity reach consumers.

Technical features and control

SmartValves rely on power electronic modules that can inject controlled voltages or adjust series impedance to change how much current flows through a given line. They are coordinated by control systems that communicate with grid protection and operational software, ensuring any change in flows respects safety margins and stability constraints. The devices operate automatically based on predefined settings, with operators able to override or adjust parameters when needed.

Manufacturer materials indicate that SmartValve units are designed for high reliability, with redundant control electronics and cooling systems housed in robust enclosures suitable for outdoor substation environments. National Grid’s engineering teams test the equipment thoroughly before commissioning, running through scenarios where lines trip or generators disconnect to validate that the SmartValves respond correctly and do not interfere with primary protection schemes.

Costs, benefits and payback

National Grid does not publish line-item prices for SmartValves, but the company has framed the technology as a way to reduce overall system costs by lowering constraint payments and deferring more expensive reinforcements. Industry analyses suggest that flexible power flow control can offer payback periods measured in a few years for heavily constrained corridors, depending on how much congestion is relieved and how high redispatch costs would otherwise be.

For shareholders, this means capex is directed into projects that can quickly cut operating expenses while supporting strategic aims like net-zero targets and reliability. SmartValves form part of a broader category of network innovations that regulators examine when evaluating National Grid’s investment plans and allowed returns. Regulators typically want assurance that such technologies deliver measurable benefits compared to traditional build-only approaches.

Comparison with traditional reinforcements

Historically, when a transmission line reached its thermal or stability limits, the main solution was to build a new parallel line or uprate conductors and towers. This approach remains essential for some corridors, but it is slow and often faces public opposition to new pylons. SmartValves provide an alternative by tapping spare capacity on existing lines elsewhere in the network, effectively increasing cross-section flow limits without visible new infrastructure.

In public reports, National Grid has described flexible power flow control as complementing, not replacing, conventional reinforcements. For example, a region may still require a new 400 kV route, but SmartValve deployments can buy time, reduce congestion in the interim, and help fine-tune flows once the new line is built. This layered approach can smooth investment profiles and reduce the risk that new hardware is underutilized because network flows evolve differently than originally forecast.

Operational experience to date

By mid-2020s, National Grid and Smart Wires had completed multiple SmartValve installations, including projects in the North of England and in interconnection corridors that link Scotland’s wind resources to load centers further south. Operational experience from these sites feeds into planning for further deployments. Engineers collect data on how often the devices adjust impedance, how much congestion is relieved, and how this translates into reduced constraint costs.

National Grid has also used SmartValve performance to refine models of the transmission network. When the product changes flows, planners can compare measured results with simulations, improving the accuracy of power flow studies. This helps in designing future expansions and in assessing other technologies like dynamic line ratings or battery-based grid support, which might be deployed alongside SmartValves.

Interaction with other flexibility tools

SmartValves do not operate in isolation. National Grid increasingly combines them with other flexibility tools such as real-time thermal ratings, automatic generation control and demand-side response. For instance, when a corridor approaches its limit, the control system can simultaneously adjust SmartValves to redirect flows and call on flexible generators or consumers to change output or demand. This layered response reduces stress across the network.

As more interconnectors link the UK to continental Europe and Ireland, power flows will become more complex. SmartValves can help manage these cross-border movements by guiding electricity through internal routes that minimize congestion near interconnection points. The equipment thus plays a role in ensuring that new cross-border capacity is used efficiently and that domestic constraints do not negate the benefits of interconnectors.

Regulatory and policy backdrop

Ofgem, the UK energy regulator, examines technologies like SmartValves in the context of its RIIO price control framework, which encourages innovation and efficient network operation. National Grid submits business cases for such investments, arguing that they reduce total system costs and support decarbonization, reliability and consumer outcomes. Approval depends on demonstrating that the product delivers net benefits compared to alternatives like building additional lines.

Policy documents related to the UK’s net-zero strategy highlight the need for both new infrastructure and smarter use of existing assets. SmartValves fall squarely into the latter category. They are one of several tools that can increase the network’s effective capacity without major visual changes, which can be sensitive in rural areas where new pylons might face public resistance.

Grid resilience and contingencies

SmartValves can also support resilience by dynamically adapting flows when elements of the network fail or are taken out for maintenance. If a major line trips, control systems can adjust valves on remaining routes to keep power flowing within safe limits. This does not eliminate the need for redundancy, but it can reduce the risk of overload-induced cascading failures.

National Grid includes SmartValve behaviour in its contingency planning. Simulation tools model scenarios such as storms damaging multiple lines or unexpected generator outages. These models incorporate how SmartValves would respond, helping dispatchers prepare operating strategies. For example, they might pre-position valve settings ahead of forecast extreme weather to reduce stress on vulnerable corridors.

Environmental and community aspects

Although SmartValves are compact compared to full substation rebuilds, they still require civil works and bring more equipment into communities near substations. National Grid typically engages with local stakeholders when installing new hardware, explaining what the cabinets do and addressing concerns about noise, visual impact or electromagnetic fields. Because SmartValves sit inside existing sites, the incremental impact is usually smaller than building entirely new overhead lines.

From an environmental perspective, the main benefit lies in enabling more renewable energy to move through the grid without curtailment. Curtailing wind or solar when the network is constrained wastes low-carbon electricity and can undermine investor confidence in new projects. By helping relieve those constraints, SmartValves indirectly support further renewable investment and contribute to lower overall emissions from electricity supply.

Future development of SmartValves

Smart Wires continues to develop its SmartValve product line, with improvements in power electronics, control algorithms and integration with grid software. As these enhancements come through, National Grid can upgrade existing installations or deploy newer versions in additional locations. Over time, this could create a broader mesh of controllable flow points across the transmission network.

There is also potential for SmartValves to integrate more tightly with forecasting tools. If algorithms can predict future congestion based on renewable output, demand and interconnector flows, they could adjust valve settings proactively rather than reactively. This would further reduce constraint costs and improve stability by smoothing flows before they hit limits.

What this means for investors

For holders of National Grid PLC stock, SmartValves represent one strand of the company’s strategy to modernize the grid while managing capital intensity. Instead of relying solely on new build projects, the operator invests in flexible technologies that can re-use existing corridors and cut operating costs. These investments sit within regulated asset bases and can influence allowed returns under price control decisions.

On the London Stock Exchange, the National Grid PLC share is part of the utilities segment and its valuation reacts not just to headline revenue and profit figures but also to regulatory outcomes and perceived execution on infrastructure plans. SmartValves will not move the share price on their own, but they contribute to the narrative that National Grid is equipping its network to handle the transition to low-carbon electricity while keeping an eye on efficiency.