We built this synchronicity … but what now?

The alternating current (AC) transmission age started in 1891 through collaboration and perseverance. This transmission method has transformed the world, led us to the brink (or over the brink) of a climate disaster, and provides the backbone for a future founded on abundant renewable resources (in Australia, at least). Collaboration and perseverance are now required to ensure the continued utility of the grid.

Synchronous machines have always been the driving force in the grid. These elegantly simple electrical machines sit in powerhouses around the globe using their century-old technology (nearly 150 years, in fact) to convert mechanical energy into electrical energy to power the computer that I’m using to type this.

There’s a romance to these machines. It’s more than nostalgia. They spin, as the name suggests, in synchronism. If one of them falters, all the rest pick up the slack. The only connection they need is the power lines. This robustness is central to the way our electricity grids have operated for over 130 years – but the influence of synchronous machines is slowly being eroded.

The most obvious erosion of the influence of synchronous machines is their displacement by inverter-based renewable (IBR) technologies as solar, wind and battery energy storage (BESS) installations proliferate. A less obvious erosion of their influence is the diminishing understanding and appreciation of synchronous technology within the industry. This lack of understanding by engineers, planners and regulators of the fundamental building blocks of the electricity grid is starting to show. 

This might sound like the curmudgeonly ranting of yesterday’s engineer as technology passes them by. Maybe it is … but, rather than dwell on negatives, let’s look at what synchronous machines bring to the power system.

• System strength

The fundamental difference between synchronous machines and IBR is thermal inertia. Typical synchronous machine design can sustain high levels of over-current for a relatively long time (seconds) compared to IBR units (milliseconds). This difference allows synchronous machines to provide a strong ‘natural’ response to voltage variations in the power system without threat of overload and damage. Transmission protection systems – and therefore grid security and safety – rely on this characteristic.

There are alternatives. Overload capacity can be built into inverters, but this is expensive. Dedicated inverter-based devices such as static synchronous compensators (STATCOMs) can be used to provide fault response.

• Inertia

Synchronous machines spin. Their spinning bits (rotors) have mass, so they have mechanical inertia. This mechanical inertia doesn’t require a control system to provide an inertial response. The inertial response from a synchronous machine is a known, predictable quantity, regardless of voltage.

IBRs can provide synthetic inertia and, when voltage is healthy, can out-perform synchronous units. When voltage is not nominal, the same current limitations that affect the IBRs’ ability to deliver fault level can also restrict the effectiveness of synthetic inertia delivery.

• Robustness

The previous two characteristics – system strength and inertia – show the support that synchronous machines can provide to the power system during disturbances. The synchronous machine can deliver these supports across a wide range of power system disturbances to voltage and frequency.

IBRs typically rely on fast controls to manage their response to system disturbances. Under some extreme conditions these controls may not be fast enough or well enough tuned to manage. While tuning is important to synchronous machine performance, often it has a second-order effect or adds robustness over and above the natural response.

Displaced but not superseded

Understanding the inherent dynamics of synchronous machines gives power system engineers a better appreciation of these machines’ contribution to power system stability. Regulators should be mindful of the reduced risk (and mostly advantages) to system security that synchronous machines offer relative to IBRs. This is despite the uncontrollable nature of synchronous machines. That is, physics dictates the stabilising effects from synchronous machines whereas control algorithms determine whether an IBR can stabilise or destabilise. Controller model accuracy is therefore more important for IBRs than it is for synchronous machines where transient stability or electro-mechanical transient time frames are considered.

Better understanding of synchronous machines should lead to more appropriate rules relating to dynamic response to system events. Overly specific requirements for fault ride-through, power recovery post-fault, and maintenance of real and reactive power during voltage disturbances may all lead to needless protracted negotiations over access standards. This slows down the progress of the energy transition, frustrates otherwise helpful development, and diverts resources towards trivial considerations rather than focusing on issues of greater importance.

Synchronous machines will play a role in the energy grid of the future. Our industry needs to maintain expertise and regulatory frameworks that allow this technology to continue providing the grid with vital stabilisation and robustness.

ABOUT THE AUTHOR

Donald has over 20 years’ experience providing advice on regulatory and technical requirements for generators, substations and transmission systems. He has worked for all areas of the electrical industry, including generators, equipment suppliers, customers, NSPs and market operators. Donald specialises in the performance of power systems. His experience in generating units, governors and excitation systems provides a helpful perspective on how the physical electrical network behaves.

‘Dams for People, Water, Environment and Development’ – some reflections from ICOLD 2024

Entura’s Amanda Ashworth (Managing Director) and Richard Herweynen (Technical Director, Water) recently attended the International Commission on Large Dams (ICOLD) 2024 Annual Meeting and International Symposium, held in New Delhi. Amanda presented on building dam safety capability, skills and competencies, while Richard presented on Hydro Tasmania’s risk-based, systems approach to dam safety management, and the importance of pumped hydro in Australia’s energy transition. 

Here they share some reflections on ICOLD 2024 …

Richard Herweynen – on the value of storage, ‘right dams’, and stewardship

At ICOLD 2024 we were reminded again that water storages will be critical for the world’s ability to deal with climate change and meet the growing global population’s needs for food and water. We can expect greater climate variability and therefore more variability in river flows, which means that more storage will be needed to ensure a high level of reliability of water supply. Without more water storages to buffer climate impacts, heavily water-dependent sectors like agriculture will be impacted.

To slow the rate of climate change, we must decarbonise our economies – but without significant energy storage, it will be difficult to transition from thermal power to variable renewable energy (wind and solar). Pablo Valverde, representing the International Hydropower Association (IHA), said at the conference that ‘storage is the hidden crisis within the crisis’. There was a lot of discussion at ICOLD 2024 about pumped hydro energy storage as a promising part of the solution. It is also important, however, to remember that conventional hydropower, with significant water storage, can be repurposed operationally to provide a firming role too. Water storage is the biggest ‘battery’ of the world and will be a critical element in the energy transition.

With the title of the ICOLD Symposium being ‘Dams for People, Water, Environment and Development’, I reflected again on the need for ‘right dams’ rather than ‘no dams’. ‘Right dams’ are those that achieve a balance among people, water, environment and development. In the opening address, we were reminded of the links between ‘ecology’ and ‘economy’ – which are not only connected by their linguistic roots but also by the dependence of any successful economy on the natural environment. It is our ethical responsibility to manage the environment with care.

When planning and designing water storages, we must recognise that a river provides ecological services and that affected people should be engaged and involved in achieving the right balance. If appropriate project sites are selected and designs strive to mitigate impacts, it is possible for a dam project’s positive contribution to be greater than its environmental impact, as was showcased in number of projects presented at the ICOLD gathering. Finding the balance is our challenge as dam engineers.

The president of ICOLD, Michel Lino, reminded delegates that the safety of dams has always been ICOLD’s focus, and that there is more to be done to improve dam safety around the world. At one session, Piotr Sliwinski discussed the Topola Dam in Poland, which failed during recent floods due to overtopping of the emergency spillway. Sharing and learning together from such experiences is an important benefit of participating in the ICOLD community.

Alejandro Pujol from Argentina, who chaired one of the ‘Dam Safety Management and Engineering’ sessions, reflected that in ICOLD’s early years the focus was on better ways to design and construct new dams, but the spotlight has now shifted to the long-term health of existing dams. It is critical that dams remain safe throughout the challenges that nature delivers, from floods to earthquakes. In reality, dams usually continue to operate long beyond their 80–100 year design life if they are structurally safe, as evidenced in the examples of long-lived dams presented by Martin Wieland from Switzerland. He suggested that the lifespan of well-designed, well-constructed, well-maintained and well-operated dams can even exceed 200 years. As dam engineers, no matter the part we play in the life of a dam, we have a responsibility to do it well.

From my conversations with a number of dam engineers representing the ICOLD Young Professional Forum (YPF), and seeing the progress of this body within the ICOLD community, I believe that the dam industry is in good hands – although, of course, there is always more to be done. I was pleased to see an Australian, Brandon Pearce, voted onto the ICOLD YPF Board.

Another YPF member, Sam Tudor from the UK, reminded us in his address of the importance of knowledge transfer, the moral obligation we all have especially to the downstream communities of our dams, and our stewardship role. He was referencing his experience of looking after dams that are more than 120 years old – all built long before he was born. Many of our colleagues across Entura and Hydro Tasmania feel this same sense of responsibility and pride when we work on Hydro Tasmania’s assets, which were built over more than a century and have been fundamental to shaping our state’s economy and delivering the quality of life we now enjoy. It is up to all of us to carry the positive legacy of these assets forward with care and custodianship, for the benefit of future generations.

Amanda Ashworth – on costs and benefits, dam safety, and an inclusive workforce

Like Richard, I found much food for thought at ICOLD 2024. For me, it reinforced the need to accelerate hydropower globally, particularly in places where the total resource is as yet underdeveloped. To do so, we will need regulatory frameworks that support success – such as by monetising storage and recognising it as an official use – and administrative reforms that ease the challenges of achieving planning approvals, grid connection agreements and financing for long-duration storage. We must encourage research and development to move our sector forward: from multi-energy hybrids to advanced construction materials and innovations to improve rehabilitation.

In particular, I’ve been reflecting on how our sector could extend our thinking and discourse about the impacts and benefits equation beyond the broad answer that dams are good for the net zero transition. How can we enact and communicate the many other potential local environmental and social benefits and long-term value from dams?

Much of the world’s existing critical infrastructure came at a significant financial expense as well as social and environmental costs – so it is our obligation to pay back that investment by maximising every dam’s effective life. When we invest in extending the lifespan of dam infrastructure through effective asset management and maintenance, and when we maximise generation or the value of storage in the market, we increase the ‘return on investment’ against the financial, social and environmental impacts incurred in the past.

Of course, the global dams community must continue to prioritise dam safety and work towards a ‘safety culture’. I was pleased to hear Debashree Mukherjee, Secretary of the Ministry of Jal Shakti, celebrate the progress on finalising regulations across states to enact India’s Federal Dam Safety Act and establishing two centres of excellence to lift capacity across the nation. Dam safety depends on well-trained people with the right skills and competencies to comply with evolving standards, apply new technologies, and respond effectively to changing operational circumstances and demands. 

I also enjoyed hearing from ICOLD’s gender and diversity committee on its progress, including updates from around 14 nations on their efforts to build a more inclusive renewable energy and dams workforce. This is front of mind for us, as we step up Entura’s own focus and actions on gender equity throughout our business this year.

The challenges facing our dams community – and our planet – are enormous, but there is certainly much to be excited about, and we look forward to continuing these important conversations over the next year.

From Richard, Amanda and Entura’s team, many thanks to the Indian National Committee on Large Dams (INCOLD) for organising and hosting this year’s ICOLD event, supporting our sector to build international professional networks, and facilitating the sharing of experiences and knowledge across the globe – all of which are so important for growing the ‘ICOLD family’ and supporting a safer, more resilient and more sustainable water and energy future.

Growing the future of hydropower – observations from a career in the industry

Entura’s Senior Principal Hydropower, Flavio Campos, knows hydropower inside out. Flavio has recently joined Entura, after working around the world on significant hydropower projects ranging from 30 MW to a whopping 8,240 MW. We asked him to share some of his hydropower journey, what excites him about the future of the sector, and what’s different about conventional hydropower and pumped hydro in supporting the clean energy transition …

When I immigrated from Brazil to Canada in 2012, it was no accident that I settled in Ontario, near Niagara Falls. I had taken a job with a consulting firm that had a hydropower hub strategically located in the Niagara region due to its long history of hydropower.

The Niagara region is the home of the Adams Power Plant, completed in 1886 – the first alternating current (AC) power plant built at scale, delivering an installed capacity of 37 MW at 2,200 V. The voltage is stepped up by a transformer to 11,000 V, allowing for an economic transmission line reaching to the city of Buffalo, NY, 32 km away. The concept was launched by engineer Nikola Tesla in collaboration with George Westinghouse, beating Thomas Edison’s bid, which was based on a direct current (DC) system. Tesla’s dream of harnessing the awesome power of Niagara Falls was realised by the end of the 19^th century, when hundreds of small hydropower plants emerged and multiple forms of electricity utilisation spread across the world.

The hydropower boom, led by Brazil and China

When I started my career in the hydropower industry in 1995, I could feel the ongoing impact of the great hydropower boom that was led by Brazil and China through the 1970s and 1980s. In 1999, I was construction manager for Tucurui Dam, one of the biggest hydropower plants in Brazil and the world at that time (now ranked 8^th in the world), delivering a total installed capacity of 8,240 MW. As part of my role, in order to raise production to the expected rates, I was able to visit China’s Three Gorges Dam during construction and learn about their techniques and massive concrete operations.

In the 1990s, Brazil’s hydropower industry had plenty of experienced professionals, from construction trading foremen and general superintendents to highly educated engineering professionals from whom I had the privilege to learn.

Since those glorious decades, global hydropower capacity has increased significantly. The strongest period was 2007 to 2016, when more than 30 GW was added per year on average. Since 2017, the industry has slumped to only 22 GW per year on average, with only 13.7 GW installed in 2023. However, it is interesting that of the new 13.7 GW, 6.5 GW was delivered as pumped hydro energy storage.

A new wave of pumped hydro

At a HydroVision International conference in Portland, Oregon, in 2019, I noticed that pumped hydro was a significant topic of discussion. The conference highlighted several factors making pumped hydro projects attractive for the clean energy transition: the ‘battery’ feature itself which helps to balance supply and demand, its contributions to grid stability, its lower environmental impact compared to conventional hydropower, the availability and efficiency of variable-speed units, and the cost comparison against other types of batteries.

Projections of a new wave of pumped storage soon evolved from conference coffee-break chatter to reality: in 2022, more than 10 GW of pumped hydro was delivered, the most ever achieved by the industry. Most of this has been delivered in China, where top-down policies imposed by government can deliver rapid results. Other countries operating on a more open-market basis need to improve the mechanisms to foster pumped hydro so that it can support the grid effectively as other variable renewable energy (VRE) sources, such as wind and solar, proliferate.

There is now consensus that pumped hydro is a necessity for grids to cope with increasing amounts of VRE– and the need is urgent. Pumped hydro, however, requires significant upfront investment in civil works and time to implement. Studies by the IHA indicate that besides the inherent need for additional pumped storage in the grid, the world’s conventional (non-pumped) hydropower installed capacity must double by 2050 in order to achieve net-zero transition targets. This will be challenging, given such a low level of new hydropower worldwide in recent years, and the fact that the most attractive sites have been already developed.

There is also opportunity to re-imagine existing conventional hydropower plants to make the most of their natural battery and firming potential – by operating flexibly to support firming VRE rather than generating for maximum volume. Even where there is no market mechanism to specifically monetise this value, it could be rewarded for national or regional outcomes.

How can we achieve the much-needed growth in conventional hydro and pumped hydro?

Conventional (non-pumped) hydropower has long been recognised for clean energy and the long life of the infrastructure. The challenge now is to identify, gain approvals and sustainably deliver new projects in a world where human occupation is growing fast and reaching into the most remote corners of watersheds. Governments and regulators must assess cost benefits against the social and environmental impacts before giving the green light to new hydropower projects.

Developing pumped hydro can be more flexible, especially when it is a closed-loop system that doesn’t depend on water flows, except for first-time filling and for topping up the losses caused by evaporation. Pumped hydro is not new – in fact, it has existed for more than a century. What is new, however, is the challenge of fostering pumped hydro development at the rate needed.

The IHA has helped clarify what is needed for the industry to develop pumped hydro faster. The IHA’s Guidance Note delivers recommendations to reduce risks and enhance certainty, supporting market players to better understand the issues.

Another interesting initiative in the hydropower journey is XFLEX Hydro, a European initiative which brought together 19 entities such as IHA, EDP, EDF, Alpiq, Bechtel and others, with the objective of increasing hydropower capabilities and flexibility to cope with changing grid profiles. X-Flex has launched 7 pilot projects already – and 4 of these are pumped hydro. This combined initiative has illustrated two important areas of focus that can benefit market players and accelerate uptake:

1. The need for a supportive regulatory regime: Policy-makers and other stakeholders need to facilitate the development of regulations or market mechanisms that fairly compensate pumped hydro, as well as conventional hydropower, such as ‘price cap and floor’ mechanisms, compensation for stability features provided by hydropower, and expediting the approval process while ensuring that social and environmental impacts are minimised and mitigated.
2. The advantages of evolving technologies, including:
   • variable-speed units, increasing flexibility
   • hydraulic short-circuit operation, in which the plant can pump and generate simultaneously
   • hydro/battery hybrid system, in which the battery works along with hydropower and enhances plant flexibility
   • digital/AI control platforms, which can improve the overall grid efficiency and reduce downtime.

Hydropower for a better future

The challenges of rapidly building out new conventional hydropower and pumped hydro are huge. Yet, where there is a will, there is a way. Those of us who understand and believe in the benefits of conventional hydropower and pumped hydro have a duty to bring communities along on the journey and to help build a better future for the next generations.

We look forward to bringing you more of Flavio’s insights into conventional hydropower and pumped hydro in future articles. Flavio is currently contributing to a number of Entura’s assignments including supervising construction on the Genex Kidston PHES project in Queensland, for which Entura is the Owner’s Engineer, and being a key adviser on the Tarraleah upgrade as part of Hydro Tasmania’s Battery of the Nation program.

Understanding the business risks of small dams and weirs

Small dams may pose significant business risks that are often under-appreciated, even if these dams don’t pose a safety risk to the community. Managing risk is a key part of running any sustainable business and understanding how to mitigate risks requires that they are properly identified, analysed and evaluated.

The Guidelines on Risk Assessment prepared by ANCOLD (Australian National Committee on Large Dams) provides a detailed process for quantitative analysis of dam safety risks for large high-consequence dams, but adopting this process for small dams and weirs can be costly and may not be clearly justifiable.

For owners of small dams, ANCOLD has a number of other guidelines that can be useful for managing these dams, including Guidelines on the Consequence Categories for Dams and Guidelines on Dam Safety Management. Assigning a consequence category for a small dam can be a useful first step in understanding the risks – and will consider the impacts on community safety, on the environment, on the dam owner’s business, and on other social factors including impacts on health, community and business dislocation, loss of employment and damage to recreational facilities and heritage.

The consequence categories are graded from ‘Low’ to ‘Extreme’. These categories are used for a number of purposes including:

• regulatory requirements (depending on which state the dam is in)
• recommended surveillance and monitoring activities
• maintenance and operational requirements
• spillway flood capacity
• dam design standards.

The focus of ANCOLD’s consequence category guidelines is on wider community safety and impacts, but not on the dam owner’s business. This potentially leaves the dam owner exposed to significant unidentified business risks. Ideally, these should be managed consistently alongside all the other business risks.

A structured approach to assessing the business risks of small dams

ANCOLD’s Guidelines on Risk Assessment is a useful starting point for undertaking a business-focused risk assessment of small dam assets. As with all risk assessments, it is useful to follow a structured approach, including the following steps:

1. identify the hazards
2. brainstorm the failure modes
3. estimate the likelihood of the failure
4. estimate the consequences of failure
5. evaluate the risks
6. develop risk mitigation measures.

Such a risk assessment approach is ideally completed with a dam engineer working closely with the business owner to capture both the dam engineering and the business-specific knowledge. 

1. Hazards

Dams need to be properly designed, constructed and maintained to continue to perform their function safely. It is essential to avoid becoming complacent. Floods are a significant hazard to all dams and cause around 50% of all failures in large, well-engineered embankment dams. Small dams are often constructed with no or minimal engineering input into the design or construction and as a result may have inherent defects that may not manifest themselves until years later.

Dams in general do not require a lot of maintenance; however, a lack of suitable maintenance can lead to failures. A key maintenance activity is management of vegetation so that trees do not establish themselves in the embankment. Tree roots can create leakage paths that could lead to piping or internal erosion, and ultimately to a failure.

2. Failure modes

A key part of the expertise of a dams engineer is understanding how different types of dams can fail, which is crucial for identifying potential failure modes. The ANCOLD guidelines on risk assessment recommend completing a site inspection of the dam to help identify the key ways in which the dam could fail. The inspection should be conducted with the dam owner to look for evidence of failure modes, such as:

• deformation or cracking, which may indicate issues with the stability of the dam
• wet areas or flows through the dam, which may indicate a piping failure
• spillways where the original crest is filled in or raised to increase storage in the reservoir, which can often be an area of concern
• erosion close to the dam from operation of the spillway, which could lead to undermining and instability of the dam wall.

Typically, failure modes are identified in a workshop setting and then prioritised by criticality. The full list of failure modes is then reduced to a shortlist of those that are most critical.

3. Likelihood of failure

ANCOLD’s Guidelines on Risk Assessment provides an approach that can be used for detailed quantitative risk assessments; however, such approaches require significant effort to apply and can be costly. For small dams, it can be more appropriate to use a risk matrix approach, similar to that outlined in the Australian standard AS ISO 31000 Risk Management.

Typically, most businesses have a standard risk assessment procedure that can be adapted to give a qualitative or semi-qualitative assessment of likelihood. An experienced dams engineer will be able to assign a likelihood for each of the credible failure modes based on engineering judgement and some simple calculations (e.g. using regional flood estimates and estimates of the spillway discharge capacity). Failure modes for dams that are well designed and constructed will often have a likelihood rating of ‘Rare’ or ‘Unlikely’. The likelihood may be higher for dams in poor condition or with identified deficiencies.

4. Consequences of failure

A business risk assessment focuses on the consequences to the business, rather than the wider community, if the small dam were to fail. This will be unique to each business and will need input from the owner. It can be assessed by working through a series of questions about the need for the dam and its purpose – for example:

• What is the water in the dam used for? Can the business function without the water or the storage space in the dam?
• Are there alternative sources for the water that can be quickly accessed, and will these be sufficient for normal operations or would it be necessary to reduce operation?
• Is there business infrastructure downstream of the dam, and could a failure of the dam cause failure of these assets (e.g. pumping stations, water treatment plants or other dams) that would impact business operations? Can the business operate without these assets?
• How will customers be affected and what are the reputational consequences of not being able to supply or only partially supply?
• What are the financial implications for the business, and is there insurance that would cover the cost of the event, including consequential losses?
• How long would it take to replace the dam (including refilling) and the other assets?

5. Evaluation of risks

Using the business’s standard risk assessment tool enables comparison of the small dam risks against other business risks on a consistent basis (e.g. safety risks to employees). The level of risk will indicate the urgency of addressing the risk. This process allows a clearly articulated justification to be presented to the business for putting in place any required mitigations. It also enables the owner to focus on the key business risks rather than become distracted by issues with lower risk.

6. Risk mitigation

Mitigations can address either likelihood or consequences and will need to be tailored to the specific risks and the business needs. Addressing the risks by reducing the likelihood will typically involve physical works to the dam – for example, increasing the size of the spillway to reduce the likelihood of an overtopping failure, or managing vegetation to reduce the likelihood of a piping failure.

Where reducing the likelihood is not practical or not sufficient, addressing the consequences may be an effective approach. Addressing the consequences may involve options such as securing alternative water supplies, contingency planning to reduce impacts on customers, or insurance to cover the financial losses.

Bringing it all together for better business insights

Entura has undertaken qualitative and semi-qualitative small dam risk assessments for a number of clients in a cooperative environment to bring together our dams engineering expertise with the owner’s knowledge of their business. This is a cost-effective approach that has provided clarity on the specific business risks related to small dams, allowing targeted risk mitigation measures to be put in place. The process has provided important insights enabling owners to justify business decisions and reduce their overall business risk exposure.

If you have small dams and would like to talk with us about assessing your business risks, contact Phillip Ellerton or Richard Herweynen.

About the author

Paul Southcott is Entura’s Senior Principal – Dams and Headworks. Paul has an outstanding depth of knowledge and skill developed over more than 3 decades in the fields of civil and dam engineering. He is a highly respected dams specialist and was recognised as Tasmania’s Professional Engineer of the Year in Engineers Australia’s 2021 Engineering Excellence Awards. Paul has contributed to many major dam and hydropower projects in Australia and abroad, including Tasmania’s ‘Battery of the Nation’, the Tarraleah hydropower scheme, Snowy Hydro, and numerous programs of work for water utilities including SeqWater, Sun Water and SAWater. His expertise is a crucial part of Entura’s ongoing support for upgrade and safety works for Hydro Tasmania’s and TasWater’s extensive dams portfolios. Paul is passionate about furthering the engineering profession through knowledge sharing, and has supported many young and emerging engineers through training and mentoring.