Risk management at Elia Transmission Belgium includes continuous monitoring of key transformers

After a 12-month trial with Vaisala’s latest transformer monitoring technology, the company managing Belgium’s power transmission network has now deployed continuous monitors at its larger transformers as part of its enterprise risk management plan.

Elia operates the Belgian high-voltage transmission grid (30 kV to 400 kV), which comprises over 8,903 km of overhead lines and underground cables, as well as hundreds of transformers. Power generation and consumption are carefully balanced, and the company has achieved a service reliability level of 99.99 %.

Elia’s mission is to drive the energy transition by designing, building, operating, and advising on reliable, cost-efficient, and future-proof power systems across borders and sectors. The reliability of transformers is central to that mission.

The challenge

At Elia, Enterprise Risk Management is part of an integrated framework of internal controls that ensures the company’s operations are conducted in a controlled, efficient, and sustainable manner by identifying, assessing and managing risks across the business.

Transformers can fail or become damaged as a result of a specific incident (overloading, lightning, severe weather etc.) causing electrical, mechanical, or thermal faults that can damage transformer components. These faults can generate gases in transformer oil. However, other faults may develop more slowly and are therefore harder to detect. Long-term deterioration occurs as a result of air leaks or the breakdown of transformer insulation or paper, which also generates gases within the transformer oil. The measurement of these dissolved gases is a key indicator of transformer condition.

The traditional test method involves the manual collection of oil samples at regular intervals for laboratory analysis. This spot sampling method provides an indication of dissolved gases and oil quality at a single point in time, leaving intervals where developing faults can go undetected.

With a large fleet of transformers, Elia implements a condition-based maintenance policy to support asset reliability, guide renewal decisions, and minimize the risk of outages.

As part of this, large transformers are equipped with continuous dissolved gas analysers (DGAs). As a result of a comparison between different suppliers, testing reliability and accuracy, Elia selected Vaisala’s DGA OPT100 Optimus.

12-month Vaisala DGA trial

Elia discussed the limitations of their existing DGA monitors with Talenco, Vaisala’s Belgian partner, who recommended Vaisala’s DGA OPT100 Optimus™. “Elia was keen to improve the reliability of their DGA monitors, and wanted a robust, maintenance-free solution capable of delivering 24/7 reliable data,” explains Talenco’s David Peeters. “They also expressed frustration with the amount of maintenance required by their existing instruments; not just because of the equipment and labour involved, but also because of the increased lifetime costs of these devices,” David adds. “Vaisala’s OPT100 was the clear choice because it offered consistent, stable and reliable measurements without maintenance, lowering costs and reducing risk.”

Working closely with Talenco, Elia thoroughly tested the OPT100 for a one-year period. During this time, oil samples were taken from the transformer every 3 months for comparison with OPT100 data.

“The results clearly demonstrated the accuracy and stability of the OPT100,” says David Peeters. “This provided Elia with greater confidence in the capabilities and reliability of OPT100.”

The trial included a simulated power outage, which the OPT100 detected, prompting automatic self-diagnosis and restart, with no reset or manual restart needed – a feature that would save unnecessary travel for the maintenance team. In addition, historical data and trend analysis were preserved, including Duval triangles for DGA interpretation.

Summary

Transformers are generally very reliable, with typical operational lifespans exceeding 40 years. However, with exposure to high voltages, varying loads, and environmental stress, their reliability depends on condition monitoring to prevent power outages.

For many transformers, yearly oil sampling and analysis can help to identify developing issues, but for strategically important transformers, a higher level of risk reduction is necessary. This is achieved by continuous DGA monitors, and the trial at Elia Transmission Belgium has shown that Vaisala’s latest technology is able to reliably detect issues before they become problems, without a requirement for regular maintenance.

ENDS