POWER TRANSMISSION Archives

Europe’s renewables milestone reveals a hidden challenge

Europe has reached a defining moment in its clean energy transition. Wind and solar are now generating more electricity than fossil fuels, marking a major shift in the continent’s energy system. However, alongside this progress comes a growing challenge: how to integrate large volumes of variable renewable power into grids that were not originally designed for it.

A milestone with a catch

In 2025, wind and solar provided around 30 per cent of EU electricity, overtaking fossil fuels for the first time. Yet despite this achievement, Germany, France and the Netherlands still curtailed a record 3.9 terawatt-hours of renewable electricity because their networks could not absorb all available generation.

As the International Energy Agency highlights, maximising the benefits of high shares of wind and solar requires greater flexibility across generation, grids, storage and demand. Without this flexibility, renewable output is increasingly at risk of being wasted, slowing the pace of emissions reductions.

For operators, this is not just a technical issue but an economic one. Curtailment means lost revenue and underutilised assets, while periods of oversupply can lead to negative wholesale prices when generation exceeds demand. The result is a system where abundant clean energy does not always translate into usable energy.

Why curtailment persists despite record generation

The underlying challenge is the variable nature of wind and solar. Unlike conventional thermal generation, output is driven by weather conditions and can change rapidly, creating mismatches between supply, demand and available grid capacity.

At the same time, Europe’s electricity networks were largely designed around centralised, predictable power sources. As inverter-based generation becomes more dominant, the assumptions that underpin traditional grid operation, particularly around voltage stability, frequency control and fault response, are being tested. When system flexibility is limited, congestion builds and curtailment becomes unavoidable.

Engineering solutions to capture more value

Solving this challenge requires more than expanding transmission infrastructure. It also depends on a broader set of engineering solutions that help maintain stability across increasingly complex and inverter-dominated networks.

At equipment and system level, resistive technologies play a key role in supporting reliable operation. Dynamic braking resistors (DBRs) help protect wind turbines and power converters by safely dissipating excess energy during transient events such as sudden load changes or grid disturbances. Neutral earthing resistors (NERs) support safety and stability by controlling fault currents during earth faults. High-voltage filter resistors help maintain power quality by managing harmonics in networks with high levels of inverter penetration.

Load banks are also widely used to test, commission and validate the performance of generation and grid infrastructure under controlled conditions
As renewable penetration increases, fault behaviour and system response become more complex and less predictable. Ensuring that equipment performs reliably under both normal and fault conditions is becoming essential to maintaining grid stability and operational confidence.

Towards a more flexible, efficient power system

Europe’s transition past fossil fuels is a significant milestone, but it also highlights a critical truth: generation growth must be matched by integration capability. Without this, increasing volumes of renewable energy risk being curtailed or underutilised, reducing both economic value and system efficiency.

Expanding grid capacity, scaling energy storage and improving overall system flexibility will be essential. Alongside these developments, engineered solutions that support fault management, power quality and real-time system control will play a crucial role in unlocking the full value of renewable energy.

To learn how Cressall’s resistive technologies support grid stability, protection and renewable integration, speak to the Cressall team.

Renewables are winning but is the grid ready?

The UK has secured record levels of solar and wind capacity as part of its 2030 renewable energy strategy. Generation is accelerating rapidly, but grid infrastructure is not expanding at the same pace. Without the right engineering solutions, renewable ambition risks outstripping operational stability.

RECORD GROWTH, GROWING CONSTRAINTS

The latest Contracts for Difference auction awarded 4.9 GW of solar and 1.3 GW of onshore wind and tidal capacity, enough to power around 16 million homes.

It’s major progress. Yet as Giles Dickson, CEO of WindEurope, has warned, you cannot have more renewable electricity without more grids.

In the UK and Ireland, limited infrastructure led to an estimated 10 TWh of renewable electricity being curtailed in 2025, enough to supply one million homes for a year. Clean power was generated but could not be transmitted, resulting in financial losses and avoidable emissions.

THE VARIABILITY CHALLENGE

Wind and solar output shifts with the weather, sometimes minute by minute. These rapid changes can cause voltage fluctuations, equipment stress and curtailment if not carefully controlled.

While renewables are now cheaper than building new gas-fired stations, cost competitiveness does not guarantee system stability. Without appropriate protection and flexibility, networks face rising strain and increasing operational costs.

A GRID WITH LESS NATURAL INERTIA

As thermal power stations retire, the system is losing the inertia once provided by large rotating machines. Inverter-based renewable generation responds faster but provides less natural damping during disturbances.

This makes networks more sensitive to voltage fluctuations and fault conditions. The transition is not just about replacing generation; it requires reengineering how the grid behaves under stress.

CONTROLLED FAULT MANAGEMENT

In inverter-dominated systems, fault currents are less predictable and influenced by control settings and asset distribution. Traditional protection schemes may not respond reliably under these new conditions.

When ground faults occur, uncontrolled current can damage transformers, cables and switchgear, potentially causing cascading failures. Protection strategies must evolve alongside renewable integration.

THE ROLE OF NEUTRAL EARTHING RESISTORS

Neutral earthing resistors (NERs) limit fault current to a safe and predetermined level. This reduces thermal and mechanical stress on equipment and allows protection systems to isolate faults quickly and effectively.

The result is fewer unexpected outages, lower repair costs and improved resilience across renewable and grid-side infrastructure.

FROM INSTALLED CAPACITY TO DEPENDABLE SUPPLY

The latest auction results are encouraging. However, long-term success depends not only on how much renewable capacity is installed, but on how reliably it operates within a changing network.

As renewable integration accelerates, collaboration between developers, network operators and specialist engineering partners will be essential to ensure clean energy growth delivers secure and stable electricity.

To find out more about strengthening renewable networks with effective resistor solutions, speak to the Cressall team.

The silent guardian

How resistors protect data centres from electrical stress

The data centre market is booming thanks to AI. According to Goldman Sachs, the explosion in generative AI means demand for data could increase 50 per cent by 2027 and by as much as 165 per cent by the end of the decade compared to 2023’s figures. It’s clear data centres are fast becoming another lifeblood utility in modern society, but what would happen if one suddenly switched off? Here, Mike Torbitt, Cressall‘s managing director, theorises just how much our world will rely on data centres in the future — and how to ensure their reliability.

Just as water, electricity and internet access have become utilities essential to modern life, information itself — stored, processed and delivered via data centres — is emerging as another utility of the digital age.

Goldman Sachs estimates that current power usage by the global data centre market sits at around 55 gigawatts (GW) and is comprised of cloud computing workloads and traditional workloads for typical business functions such as email or storage and AI.

Currently, the analyst estimates AI makes up roughly 14 per cent of this 55 GW capacity. However, when modelling future demand for these workload types, its analysts predict data centre power demand could reach 84 GW by 2027 with AI growing to 27 per cent of the overall market.

Of course, this is just one of many predictions and the crystal ball is present during any discourse on AI’s future. What appears definite though, is that the technology is transforming the way we consume information and thus the capacity of data centres.

Lights off

So, what would happen if a data centre suddenly lost power? The effects could ripple far beyond disrupted websites. Online banking, medical diagnostics, AI-powered logistics and smart energy infrastructure are just some of the many applications that rely on a continuous flow of information being processed and stored in these facilities.

For AI-specific workloads, the risks are particularly acute. Training large-scale models involves thousands of simultaneous graphics processing and tensor processing unit operations that can run for days or weeks. If power is lost mid-process and checkpointing isn’t frequent or robust, entire training runs may be corrupted or lost. Inference systems that run in real-time such as recommendation engines, chatbots or fraud detection tools can stall instantly, causing service degradation or outright failure.

Data integrity is another issue. Many applications run on distributed databases that rely on synchronous replication and consensus mechanisms. If nodes in different racks or zones go down at slightly different times, it can cause data inconsistency or split-brain scenarios, where systems disagree on the current state of data.

While most modern data centres are equipped with uninterruptible power supplies (UPS) and backup generators, a delay in switching over to backup power, a failed UPS battery bank or insufficient fuel reserves in a prolonged grid failure can all lead to downtime.

Powering resilience

As data centre workloads become more complex and the stakes of downtime more severe, electrical reliability becomes a critical point of failure and therefore, a primary design consideration. This is where passive components like resistors play a role in ensuring stable, resilient operations.

Resistor technologies such as neutral earthing resistors (NERs) are essential to protecting infrastructure and maintaining uptime. NERs are deployed to limit fault current during earth faults, preventing damage to expensive components like transformers and switchgear. In the event of a ground fault, an NER ensures the fault current is safely controlled and isolated, allowing the rest of the data centre to remain operational while the fault is addressed.

Load banks, on the other hand, are used to test and validate backup power systems by simulating real electrical loads under controlled conditions. They allow operators to verify that backup systems can deliver the required power reliably during an actual outage, without the risk of affecting live data centre operations.

Routine load bank testing can uncover issues such as fuel delivery problems, battery degradation or improper load sharing between generators — all of which might otherwise remain hidden until an emergency strikes. By identifying and correcting these issues in advance, load banks support predictive maintenance, regulatory compliance and, ultimately, system resilience.

Making the choice

Of course, not all resistor solutions are created equal. As data centres scale, operators must consider variables such as fault current levels, system voltage, spatial constraints, cooling requirements and compliance with international standards.

Selecting the appropriate NER with the correct resistance value and time rating, how long the resistor can safely carry fault current before its temperature exceeds safe operating limits, is critical for effective fault current limitation without interrupting service. Likewise, load banks must be sized to reflect real-world power demands and designed for integration with both generator and UPS systems.

Custom engineering plays a significant role in aligning these technologies with the architecture of each facility. Modular data centres, hyperscale environments and edge computing sites each present unique demands — from space and airflow limitations to maintenance accessibility. Working with experienced resistor manufacturers, like Cressall, ensures that resilience is built into the system from the ground up, not added as an afterthought.
In a digital economy that’s becoming increasingly dependent on uninterrupted data flow, choosing the right components to ensure reliability matters. As the utility of the modern world, the cost of downtime in data centres is only going to rise as our implementation of AI technologies increases. Building safety nets into systems is therefore critical and, while resistors may not be the first component that springs to mind, their role in data centre uptime has never been more important.

Learn more about Cressall’s range of resistor technologies by visiting the website

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Lessons from COP30

The critical role of grid stability in the energy transition

‘We can choose to lead, or be led to ruin,’ declared UN Secretary-General António Guterres, addressing delegates at COP30 in the rainforest city of Belém, Brazil. As the world pushes to triple renewable power capacity by 2030, attention is shifting from adding generation to preparing grids for the change. In light of COP30, Mike Torbitt, managing director of resistor manufacturer Cressall Resistors, examines the growing pressure on electricity networks and the role of grid stability technology as renewable deployment accelerates.

The world has recently seen record growth in renewable energy, with solar and wind forming the backbone of global decarbonisation efforts. Yet, despite that, COP30 delivered a clear message: the pace must quicken if we are to meet targets for 2030. Analysis from the Climate Action Tracker coalition, released at COP30, shows that “sticking to key climate pledges — tripling renewable energy, doubling energy efficiency and cutting methane emissions — could avoid nearly 1°C of global heating and significantly slow the rate of warming this century.”

Expanding renewable capacity at the pace needed to meet climate goals will demand unprecedented investment, infrastructure expansion and system upgrades. But increasing generation alone won’t be enough — the real challenge lies in ensuring that grids can handle the variable, fast-responding energy these new sources provide. Integrating that power reliably into networks that were not designed for variable energy sources is becoming the defining task of the energy transition.

The grid challenge behind rapid renewable growth

Renewable growth is radically changing the way in which electricity systems function. Solar and wind generation follow weather patterns, leading to steep rises and falls in generation that must be balanced in real time. As installations expand, these variations become more extreme, placing new stresses on equipment and system operators alike.

Today’s renewable output is constrained by congestion and capacity limits in transmission and distribution systems, limiting how efficiently the power is delivered to consumers. Storage capacity is expanding but remains far below what is required to balance supply and demand across all regions.

Without the right stability and protection technologies, high-renewable grids risk greater levels of curtailment, decreased asset lifetimes and reduced system reliability. As inverter-based generation becomes the dominant form of new capacity, networks are also losing the inherent stability once provided by conventional rotating machines. This shift makes grids more sensitive to faults, fluctuations and power disturbances, increasing the importance of technologies that can absorb, dissipate or smooth unexpected energy spikes.

Technology that makes high-renewable grids possible

This is where resistor technology becomes essential to keeping systems stable. Dynamic braking resistors (DBRs) offer a proven method for managing rapid changes in power flow, especially in systems where renewable output can increase or decrease quickly. By safely converting excess energy into heat, DBRs prevent over speeding in rotating equipment or instability in inverter-driven systems.

For wind turbines, DBRs are essential to managing sudden gusts or rapid changes in mechanical load. For solar, they support stability during cloud transients or fast inverter cycling and in storage and hybrid systems, they help maintain smooth operation during transitions or when switching between energy sources. At commissioning stage, DBRs also support system testing to ensure equipment performs safely before going live.

Cressall has decades of experience across renewable generation, grid infrastructure and transport applications, supplying DBRs engineered for long-term reliability, safety and demanding environmental conditions. As grids continue to evolve, this technology will continue to support the safe integration of new renewable capacity, especially in a future where inverter-based systems take on an increasingly large share of total generation.

What COP30 signals for the future

One of the key messages emerging from COP30 is that renewable growth must be matched by investment in modern, stable and flexible grids. The International Renewable Agency’s (IRENA) analysis reinforces this point, stating that “power system infrastructure and flexibility must expand at a much faster rate to accommodate rising shares of variable renewables”.

According to IRENA, at COP30 the Utilities for Net Zero Alliance (UNEZA) announced investment plans totalling over USD 1 trillion by 2030, with a significant emphasis on strengthening power grids and networks. This commitment from the world’s leading utilities demonstrates the scale of infrastructure transformation needed to support renewable expansion.

This has significant implications for grid operators, developers and technology suppliers. As renewables are installed more rapidly, system stress will rise and there will be greater need for proven solutions that ensure stability.

Digitalisation will play a growing role in improving forecasting and control, but physical safeguards such as DBRs will still be essential for protecting equipment and maintaining reliability.

COP30 reinforced the scale of work required to reach renewable and climate goals. But that transition cannot succeed unless grids can cope with the new realities created by variable, fast-responding, decentralised generation. Dynamic braking resistors offer a crucial layer of protection and stability, enabling renewable energy sources to be integrated in a secure and reliable way.

To find out more about the role of resistors in renewable energy generation, speak to Cressall’s experts

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