These phenomena initially manifest themselves only as a slight increase in losses and temperatures. However, if they are not detected in time, they can result in failure and costly downtime.
Today's energy sector adds a new dimension of dynamics. Photovoltaics, wind farms, and the growing electrification of life mean sharp fluctuations in power and voltage. Transformers are therefore subjected to more frequent temperature and mechanical cycles, which significantly accelerates the stress on the insulation system.
"Today's transformers do not operate in a comfortable, predictable network. Variable production from renewable sources and rapidly changing loads place much greater demands on these devices than they were designed for," warns Jan Krišpín, CEO and member of the board of directors of ORGREZ, a.s.
What happens inside when renewable energy sources increase
Short overflows from distributed sources alternate with sharp drops in production, oil expands and contracts, paper absorbency fluctuates, the loss factor (tg δ) increases, and the electrical strength of the insulation decreases. In some cases, tap changers can handle thousands of switches per year, causing them to lose their service life more quickly. In addition, local hot spots arise in less stable voltage profiles, accelerating degradation.
Classic diagnostics—oil analysis, DGA, moisture monitoring, and frequency response—show whether insulation is aging normally or at an accelerated rate. In the era of renewable energy sources, this data carries even greater weight. "If a switch is exposed to thousands of switching operations per year, this will result in an increase in contact losses and changes in the oil chemistry. That is why it is crucial to continuously evaluate data and not wait for a major problem to occur," emphasizes Jiří Brázdil, Technical Director for Electrical Power Engineering at ORGREZ.
EMTRA: hard data on actual losses
Knowing the condition of insulation is essential. But when it comes to transformer losses and efficiency, accurate electrodiagnostic measurements are decisive. That is why EMTRA was created – mobile technology for measuring losses directly during operation. Using the EMTRA method, it quickly, safely, and without unnecessarily long downtimes determines how much energy and money is actually being lost.
"EMTRA provides us with hard data that allows us to determine whether it makes sense to continue operating a transformer, refurbish it, or consider replacing it. This is doubly important in a network with renewable energy sources, because losses change with the operating mode and paper labels simply do not reflect reality after years of operation," says Jiří Gregor, Director of Business Development at ORGREZ2
Smart maintenance: when prevention saves millions
Based on data from diagnostics, monitoring, and EMTRA, a maintenance plan can be drawn up that is both logical and economically efficient. This is not a fixed list of tasks, but rather a decision about when and why to perform a specific intervention. Typical examples include:
- oil regeneration at a time when interfacial tension is rapidly decreasing and acidity is increasing,
- repair of tap changers if transition losses increase and switching times lengthen,
- Enhanced cooling, as summer peaks from renewable energy sources increase thermal stress.
Many interventions can be performed on site – without lengthy downtime and without the risk of an environmental accident during oil transport. In addition, many problems can be solved most cost-effectively when they are still in their infancy. Filtration and regeneration of insulating oil directly on site restores dielectric and chemical parameters to safe values, reduces tg δ and acidity, and increases interfacial tension. In combination with cleaning of active parts and re-inhibition, this can slow down the aging process even in environments with frequent temperature cycles.
Today, transformers operate in far more demanding conditions than they did decades ago. Continuous diagnostics, trend monitoring, the use of EMTRA, and well-thought-out intervention planning are therefore the way to ensure their reliable and efficient operation. "The goal is not to produce a protocol, but to prevent failure at the least opportune moment. That is the real added value of modern electrical power equipment maintenance," summarizes Jiří Gregor.