Two pioneering, bio-based dielectric fluids have been developed and tested: a bio-based ester fluid – derived from renewable synthetic esters – and a vegetable-based fluid – derived from carefully selected and purified vegetable sources.

The goal is to create biodegradable formulations derived from sustainable sources, allowing SST modules to operate safely at higher voltage levels.

Material compatibility tests were performed in the early months of the project to ensure uninterrupted operation. These tests demonstrated the suitability of the innovative fluids within the SST modules.

Novamont conducted an in-depth study of dielectric formulations, and the producing process was carried out on a laboratory scale. Thanks to the good results obtained, a small pilot-scale process was subsequently established, and optimised in terms of costs and technical performance.

Importantly, both formulations meet the industry's strictest safety and performance standards: IEC 61099 for ester-based fluids and IEC 62770 for vegetable-based ones.

These fluids are widely used due to their environmental and performance benefits.

From an environmental point of view, in the case of accidental spills, natural and synthetic esters are readily biodegradable – which means that long-term environmental risks are minimised. Also, they exhibit low bioaccumulation, meaning they don't build up significantly in the environment.

In addition, while being safer than mineral oils, with high flash and fire points and, as a consequence, a reduced fire risk, they ensure considerable performance benefits. Namely:

· Water absorption and Kraft paper/cardboard protection: natural and synthetic esters have a higher polarity than mineral oils, allowing them to absorb more water without compromising their dielectric properties. This reduces the risk of electrical arcing and discharges within transformers. Additionally, they can extend the lifespan of the insulating Kraft paper and cardboard used in transformers by absorbing moisture and slowing degradation.

· Low gasification: synthetic ester and vegetable-based fluids have low gasification rates.

· Comparable thermal properties: the specific heat and thermal conductivity of ester-based fluids are comparable to those of mineral oils.

· Extended equipment life: the use of synthetic ester and vegetable-based fluids can potentially prolong the lifespan of transformers and other electrical equipment.

This combination of safety advantages and great performance also allows placing transformers in urban areas where stricter fire regulations might exist.

The project partner RINA-C was involved in the Health, Safety, and Environment assessment while CERTH gathered important information to study critical aspects of SST with dielectric fluids that can bring to corona breakdown.

Ester-based dielectric fluids offer a greener alternative to traditional mineral and silicone oil formulations and represent a compelling combination of environmental benefits, safety advantages, and performance enhancements, making them a strong choice for the disruptive technology of SST transformers.

Contacts:

Project coordinator:
Jonatan Peris Rivas, CIRCE, jperis@fcirce.es

Communication Manager:
Ilaria Bonetti, ICONS ilaria.bonetti@icons.it

Erika Novellini, ICONS erika.novellini@icons.it

Project website: https://sstar-project.eu
LinkedIn: https://www.linkedin.com/company/sstar-project/

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