Why power transformers matter
Power transformers are critical components of the power system, and when a large transformer fails, the consequences can be serious for both the grid and the owner. At the same time, conditions are changing: electrification brings higher and more variable loads, power electronics creates new kinds of voltage stress, and new insulating liquids are coming into use. Many owners have an ageing transformer fleet and must decide which units to keep in service, upgrade or replace. Our field is electric power and high-voltage engineering, and we work with partners across the value chain.
Our expertise and experience
A transformer’s performance and service life depend on the interplay between material properties, design, operating conditions and stresses from the grid. We have expertise and experience in these areas:
- Insulation systems and materials: solid and liquid insulation such as cellulose, pressboard, mineral oils, esters and other new transformer liquids, and how their electrical, thermal, chemical and mechanical properties affect performance and service life
- Condition and diagnostics: condition assessment and troubleshooting of transformers and bushings using partial discharge (PD) measurements with acoustic localisation, dielectric response and analysis of insulating liquids, as well as the development of sensors and online monitoring
- Service life, risk and decision support: failure mechanisms, ageing, health indices and expected service life, the risk of fire and explosion if a transformer fails, and how measurement data, models and statistics can be combined into better decisions on operation, maintenance and reinvestment
- Dielectric strength: partial discharges, streamers and breakdown, dielectric losses (tan δ) and insulation design
- Losses, cooling and loading capability: losses and heat generation, liquid flow and cooling in windings, hot-spot temperature, dynamic loading and overloading, moisture migration and bubble formation, including in arctic conditions
- Mechanical integrity and ageing: mechanical properties of cellulose and pressboard, winding clamping pressure, thermomechanical ageing and the ability to withstand short-circuit forces
- Stresses from the power system: lightning and switching overvoltages, resonances, fast transients and the impact of power electronic converters, and protection against overvoltages, for example surge arresters and snubber circuits
- Other stresses from the grid: faults and short circuits, inrush currents and geomagnetically induced currents (GIC) during solar storms
In practice, problems often cut across these areas. We do both fundamental research and hands-on assignments for industry.
How can we help?
Do you have a transformer that is not behaving as expected, a new material or concept that needs testing, or a question about where the limits lie? Typical assignments include:
- Specialised testing of materials, insulation models, bushings and transformers in the laboratory, often with test set-ups tailored to the problem
- Field measurements and condition assessment of transformers and bushings in service, such as PD measurements that separate real defects from noise and locate the source
- Failure investigations after breakdowns, and teardown analyses of transformers taken out of service
- Qualification and comparison of new insulation materials and transformer liquids
- Assessment of how hard existing transformers can be loaded, including overloading and dynamic loading
- Measurements and studies of transient overvoltages and resonances, including overvoltage calculations with high-frequency transformer models
- Technical decision support for procurement, life extension and decommissioning
- Research and development projects with industry, nationally and internationally
We take on both well-defined testing and analysis assignments and larger research and development projects. Your question does not have to fit into a ready-made category. Many of our projects started exactly like that, with a new question from industry.
How we work
We combine experiments, field measurements and modelling, including:
- High-voltage testing: AC, DC and impulse testing, PD measurements (electrical and acoustic) and testing of transformers and bushings
- Material and dielectric characterisation of solid and liquid insulation, including dielectric response, tan δ, moisture content and ageing markers
- Specialised small-scale experiments, such as high-speed imaging of streamers in liquids, thermal and fluid-dynamic experiments on winding models, mechanical testing and ageing tests
- Field measurements on installed transformers, such as sweep frequency response analysis (SFRA) and PD measurements, and development and testing of sensors for online monitoring
- Modelling and simulation: electric field calculations, thermal and fluid-dynamic models (CFD), mechanical analyses, and moisture and ageing models; wideband, measurement-based transformer models for studying transient overvoltages in EMTP and PSCAD; and detailed winding models for simulating internal stresses and resonances
- Data-driven and hybrid models that combine sensor data and machine learning with physical knowledge
When standard methods are not enough, we develop our own test set-ups and measurement methods. Our electric power laboratories cover material characterisation, small-scale experiments and high-voltage testing of large components.
Why choose SINTEF?
SINTEF combines independent research, interdisciplinary expertise and close collaboration with industry and the public sector. For power transformers, this means:
- From materials to power system: We can follow a problem from material properties and the underlying physical mechanisms, via the insulation system and the component, to the transformer’s interaction with the grid.
- Experiments, field measurements and models under one roof: We study phenomena under controlled conditions and test whether models and methods describe real transformers.
- Long experience and close contact with industry: We have worked on transformers for many years, together with owners, manufacturers, material suppliers, grid companies and power producers, nationally and internationally. Through the Norwegian user group for power and industrial transformers, we share experience and identify new knowledge needs.
- Academic network: We have a long and close collaboration with NTNU, and take part in CIGRE and IEC standardisation work.
- An independent role: As an independent research institute, we provide an impartial, science-based basis for decisions, for example when you choose a new transformer liquid, consider higher loading or need to find out what happened in a failure.
Who do we work for?
We work for customers and partners in Norway and internationally:
- Transformer owners: grid companies, power producers and industry
- Transformer manufacturers and suppliers of components, sensors and monitoring equipment
- Suppliers of insulation materials and transformer liquids
- The Research Council of Norway and other national and international funding bodies
- The European Commission, through Horizon Europe and other European research programmes
Related pages
This competence area is linked to:
Projects
- LiPe – dielectric strength and new insulating liquids
- NewLifT – thermal properties, cooling and the use of new insulating liquids
- DynaLoad and ClampIT – solid insulation materials, mechanical properties and dynamic loading
- FastTrans and SwoP – impact of fast voltage changes and power electronics
- UPGriD – better models and utilisation of transformers and other power components
- UpLoad – opportunities and risks of transformer overloading
- Spectra – ageing and diagnostics of solid insulation materials
- ProTrafo – overvoltage protection of transformers