Specifying compact secondary substations for harsh environments

Floating solar. Image credit: ABB

To truly harness the power of nature for the generation of renewable electricity, developing power stations in harsh and remote locations is becoming increasingly common. 

Specifying compact secondary substations (CSS) for these environments requires careful consideration. They must be easy to transport, simple to install, and robust enough to deliver system longevity despite extreme temperatures, humidity and salinity.

Here, Sergi Pujol, Global Product Marketing Manager for ABB Electrification Distribution Solutions, Integrated Secondary Substations explores the primary considerations for specifying CSS for harsh environments and reflects on ABB’s role in creating one of the world’s largest floating solar farms – an award-winning project and an example of best practice specification.  

From arid deserts, to remote rural areas, to coastal environments and Alpine lakes thousands of meters above sea level, the locations we are choosing to harvest wind and solar energy are becoming more extreme.

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The natural resources in these locations are pure, uninterrupted, and often more abundant, with space to develop the wind and solar farms required to really harness the natural power available.  Put simply, these environments are not suitable for inhabitation or urbanization because of the extreme weather they experience, but they are suitable for carefully considered, conscious development in order to harness the power of nature at its greatest.

By harnessing the abundant temperatures and wind of such locations provides us with the natural power we require to responsibly fuel the growing communities we live in.

By harvesting renewable power from remote locations, power companies are able to generate cleaner power in larger quantities to fuel our growing cities.

The critical criteria of compact secondary substations in remote locations

Developing renewable power stations in harsh and difficult to reach environments requires products that are lightweight for transportation, yet robust enough to withstand extreme conditions.

It must be possible to transport products, no matter their size, in a way which is considerate to the environment it is travelling through to reach its remote destination, treacherous roads, air and boat travel should all be considered early on in the specification process before material selection begins.

Once installed, the equipment must be robust enough on the outside to protect all sensitive internal components for the duration of its lifespan with minimal maintenance or intervention, especially in hard-to-reach geographical areas.

CSS must defend sensitive electrical components against external factors such as extreme temperatures, humidity, salinity, plus environmental considerations such as gale force winds, the presence of water, animals, self-clinging plants and destructive tree roots.

As energy providers continue to unearth remote locations and responsibly develop them in a way which enables the harvesting of clean renewable energy, it is the responsibility of the supply chain to develop products and subsystems that are easy to transport to these locations and are capable of withstanding the harsh natural elements.

In doing so, we can increase our usage of renewable power in towns and cities across the world, and create safe, sustainable communities.

The habitual specification of steel, concrete and aluminium for compact secondary substations

For a standard environment, a secondary substation is most commonly constructed using steel with a habitual jump to concrete whenever a more robust solution is required. While concrete may perform better in hotter climates than steel, there are certain structural aspects of a CSS that cannot be cast in concrete such as doors and ventilation inlets. In this instance, steel will still be used, leaving weak links in the design that are often susceptible to the corrosive nature of harsh environments.

Although it remains a primary choice for many non-standard environments, reinforced concrete offers little thermoflexibility, making it prone to cracking in extremely cold temperatures and locations that experience seasonal freezing cycles.

Once cracked, concrete cannot maintain optimal performance – water will reach the steel reinforcements inside the concrete and rusting will begin, creating further corrosion and larger cracks. With the outer protective material infiltrated, the cracks in the concrete provide a water ingress risking catastrophic failure of the sensitive electrical equipment inside.

Medium voltage switchgear and low voltage switchboards are not designed to withstand exposure to external environments, and the presence of water, salinity and outdoor freezing temperatures will cause irreparable damage.

Concrete is also incredibly heavy and difficult to transport to remote and treacherous locations, increasing transportation and installation costs.

The other popular alternative, often used for the most extreme environments, is aluminium, but even though this material can outperform concrete and steel for durability in aggressive environments, it is often cost prohibitive for many specification budgets.

Both stainless steel and aluminium are also more susceptible to condensation, making them less suitable for warm environments or locations on or near water.

Many companies are looking into new methods of manufacturing and packaging to support utilities in their efforts in seeking out new locations for reliable, renewable power supply.

The evolution towards glass reinforced polyester for CSS construction

Glass reinforced polyester (GRP) is the only CSS construction material on the market designed specifically to withstand harsh environments. Commonly used for wind turbine blades, boats, cable pillars and even garden furniture, this robust, lightweight material outperforms steel, concrete and aluminium against extreme temperatures, humidity and salinity.

This polyester material is reinforced with the addition of glass fiber (or fiberglass) which is mixed into the thermosetting polyester resin in different directions. This is done under strictly controlled factory conditions and creates a material with an unrivalled inherent strength.

Stronger than all steel varieties, GRP is typically 75% lighter than steel when compared strength for strength1, and unlike concrete GRP is naturally watertight.

Keeping maintenance minimal post installation

For operators of power plants in remote locations, keeping maintenance minimal post installation should be a real consideration when choosing a secondary substation supplier.

Choosing materials and construction methods which provide a class-leading level of protection for the critical electrical components inside, means operatives will not need to travel to the remote location regularly to check and maintain the structure.

The cracks and rust associated with concrete and steel do not provide this reassurance, but GRP requires minimal monitoring and maintenance, thanks to its robust performance qualities and flexible, corrosion resistant design.  

CASE STUDY: Lac des Toules, bringing power to western Switzerland

Exposed to the natural elements at full power, Lac des Toules in the Swiss Alps was identified by local power company, Romande Energie, as the ideal location to harness clean solar power. But a successful project in a harsh location like this would require equipment that could be transported easily and once in-situ, withstand the extreme mountainous environment.

After a complex two-year construction project, the floating solar PV installation – one of the highest in the world – is now capable of generating more than 800,000 kilowatt-hours of clean solar power every year to help power western Switzerland.

Linking the floating solar panels to the grid is an eco-friendly ABB GRP UniPack-G CSS, specially designed to be lightweight, but robust enough to withstand harsh Alpine conditions.  

UniPack-G. Credit: ABB

Extreme temperatures, and humidity were all important variables when specifying equipment for this project – especially when it came to protecting sensitive electrical components inside the substation.

Because it is constructed with GRP, the UniPack-G CSS, outperforms steel and concrete for the protection of critical electronic elements such as medium-voltage switchgear, low-voltage switchboards, transformers and protection devices.

Offering superior thermal insulation and a rust-resistant design to withstand the harshest environments, the GRP construction is up to 20% more durable than alternative materials and offers the highest level of arc safety on the market.

Ideal for meeting the transportation and installation requirements of complex locations, such as this award-winning project in the Swiss Alps, GRP is four times lighter than a concrete equivalent, making it suitable for truck, crane and even boat transportation, plus installation on floating platforms

Growing cities and evolving infrastructures such as electric vehicles are fuelling a requirement for clean, renewable power in larger quantities than ever before, and remote locations are already playing a key role in serving this need.

For the power generation supply chain, this creates a demand for systems and critical components that can withstand the effects of nature at its most powerful. GRP compact secondary substations are an example of how specification is changing to meet the evolution of how and where we harvest renewable energy.

For more information on the UniPack-G from ABB, click here and to watch a video on the award-winning Lac des Toules project, click here.

1 FRP vs Steel, Aluminum, Wood, Compare To Traditional Building Materials (bedfordreinforced.com)

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