Maintenance Technology Reshaping Substation Design

How a German Grid Operator Rethought the Transformer Bund

There is one question that comes up early in every new substation construction project: how large does the transformer bund need to be?

The answer is not arbitrary. There are clear guidelines: the bund must be able to contain the entire volume of oil in the transformer, plus a margin for rainwater and, in some cases, firefighting water. It is a reasonable requirement — and the part concerning oil containment is non-negotiable.

But sizing for rainwater is another matter.

At a 110 kV substation in Germany, a grid operator decided to take a closer look at that very issue. The station was built as a reference project — a template for how future substations would be designed and equipped.

What happens if the bund never fills up?

A transformer bund does not only collect oil in the event of a failure. It also collects rainwater — day after day, year after year. In many substations, this is still handled manually: someone visits the site, checks the water level, and if the water is clean enough, it is pumped away. If it is contaminated with oil, more costly handling is required.

This consumes both time and money. But it also creates another, more structural consequence: because rainwater can accumulate quickly, the bund must be designed with generous margins. Not only for the oil itself, but for everything that may collect there before the next manual drainage cycle.

The company wanted to break that pattern. The goal was a bund that could be kept continuously at a low level — automatically, consistently, and with full traceability.

Automation that never has to guess

SIPP Node was installed at the station as a pilot project. The system manages transformer bund drainage fully automatically and measures oil content in the water second by second with an accuracy of ±1 ppm.

Water with an oil concentration below the statutory limit of 5 ppm is automatically discharged into the wastewater system. Water that exceeds the limit remains in the bund until oil levels fall below the threshold again.

Everything is logged and available online 24/7.

Manual level checks and water quality assessments are completely removed from the process.

The unexpected result

The operational savings were expected. What proved just as valuable was something else entirely.

When the bund is actively maintained at a low level — rather than emptied only occasionally — the conditions for sizing it change already at the design stage. The full containment volume is always available in the event of a failure, because the bund never has time to fill with rainwater between drainage cycles. That means the bund can be built with a smaller footprint without compromising safety margins.

The result was a substation with lower construction costs, less extensive civil engineering work — and the same ability to handle a worst-case scenario.

Maintenance digitalization does not always influence projects as early as the engineering phase. In this case, it did exactly that, helping establish a new standard for how the company plans future substations.

The project demonstrates how maintenance digitalization can influence not only operations, but also how future substations are engineered and built.

About SIPP™ Node

SIPP Node continuously monitors water and oil levels in the transformer bund, detects oil content, and automatically manages alarm and pump sequences as needed. All data is documented and visualized in the user platform — always giving operators full visibility and a complete history of the bund’s status.

The solution eliminates the need for manual inspection and replaces scheduled site visits with automated management that acts when it actually needs to. The bund is always ready to do its job — and the documentation required for regulatory compliance takes care of itself.

About Gomero

Gomero is a strategic partner for utilities looking to digitalize the maintenance of their substations. Our platform gives operators full visibility into their critical assets with real-time insights, early warnings, and the right information for field teams, whenever and wherever they need it.

We work closely with our customers to ensure the solution fits their needs today and scales with their operations tomorrow. From a single connected device to an ecosystem covering every substation — powering the transition to a more resilient and sustainable energy system.