Containment bunds for transformers

Self-extinguishing transformer oil collection trays, also for retrofitting

The transformer oil containment tray offers full compliance with EN 61936-1, AS2067, REACH and RoHS requirements. It is an alternative to concrete pits or tanks when the ground is unsuitable or a rapid solution is needed: areas where excavation is difficult, rising groundwater, tight deadlines, etc.

We also offer the refurbishment, maintenance, and sealing of existing old oil containment trays for transformers . At the same time, a self-extinguishing fire protection system can be retrofitted.

Patented self-extinguishing transformer fire protection system, also suitable for retrofitting existing concrete tanks

Transformer fires pose a significant challenge for firefighters due to the flammable transformer oil and the associated risk of explosion . Such fires can lead to massive consequential costs due to prolonged power grid outages.

Instead of using expensive automatic (firefighting) cannons to "shoot sparrows," our patented self-extinguishing containment trays, by design, smother the fire. The transformer oil flows through narrow gaps in the tray's intermediate floor, and any fire underneath is extinguished on its own. Our transformer containment trays allow the flames to extinguish naturally without the risk of reignition.

In addition to modular, self-extinguishing containment trays for transformers, we also offer the transformer fire protection system for concrete trays housing high-voltage electrical transformers (63 kVA to 400 kV).

The globally unique patented fire protection system can also be used to retrofit existing concrete troughs for transformers!

Why are self-extinguishing containment bunds important for transformers?

Self-extinguishing containment trays for transformers prevent costly and dangerous fire brigade operations involving burning transformer oil and protect surrounding equipment from damage and consequential damage (e.g., from extinguishing water).

The self-extinguishing transformer oil containment trays with integrated fire extinguishing system for electrical transformers enable the rapid drainage of dielectric substances into the tray and the natural extinguishing of flames. Suitable for transformers (between 10 and 100 MVA), neutral point coils (between 300 and 1000 A), capacitors, compensated impedance transformers, autotransformers, auxiliary transformers, and frequency feed-in transformers.

"When transformers or substations catch fire, firefighting is always a very delicate and difficult matter. Since water conducts electricity, it is not a suitable extinguishing agent and is even prohibited in some cases . For example, if a solid jet of water hits live parts, the voltage could arc and thus injure or even kill the firefighter." (Source: EmiControls - Fire protection in substations and at transformers )

"Extinguishing power transformer fires is complex and can be very time-consuming. This was particularly evident in the fire involving a 500 megavolt-ampere (MVA) transformer in Abu Dhabi on April 17, 2014. Due to the size of the transformer and the burning, leaking transformer oil, the scene was not fully under control until April 19, 2014. One of the most common causes of transformer fires is the loss of the oil's dielectric properties. This can lead to the formation of an electric arc. Part of the oil filling evaporates within milliseconds. The pressure increase destroys the transformer casing, and the burning oil escapes." This is also known as "thermal runaway" ....

The particular challenges for firefighting are

• Extensive liquid fire in the transformer's containment area.
• The transformer oil continues to flow, burning.
• The system is still under high voltage
• The heated metal parts and burning solid materials can cause the liquid fire to reignite.
• The transformer is usually difficult to access .

(Source: Berlin Fire Department: Research project) AERIUS: Fires at high-voltage power plants & Oil transformers ​

Frequently Asked Questions (FAQ) – Transformer Oil Containment Bunds, Berms & Tanks

1. What is a transformer containment bund?

A transformer containment bund is a secondary containment system designed to retain insulating oil or other dielectric fluids released from a transformer due to leakage, failure, or maintenance activities. Bunds prevent oil from spreading into soil, groundwater, or drainage systems and are a key element of environmental protection.

2. What is the difference between a bund, a berm, and a containment tank?

The terms are closely related but often used differently depending on region and application:

• Bund: A rigid or modular enclosure, commonly steel or concrete, surrounding a transformer.

• Berm: A raised barrier or flexible containment system, often used for temporary or retrofit applications.

• Containment tank / basin: A closed or semi-closed oil retention structure designed to collect large volumes of transformer oil.

All serve the same purpose: secondary oil containment.

3. Why is oil containment required for transformers?

Transformer oil containment is essential to:

• prevent environmental contamination,

• comply with water and environmental protection regulations,

• reduce cleanup costs and liability,

• support transformer fire safety by controlling oil spread.

Oil-filled transformers without containment represent a significant environmental and fire risk.

4. Which transformers require bunds or containment systems?

Containment bunds, berms, or tanks are typically required for:

• medium-voltage transformers,

• high-voltage transformers,

• power transformers rated approx. 10–100 MVA,

• oil-filled transformers in substations, solar plants, wind farms, and industrial facilities.

The decisive factor is oil volume, not only transformer rating.

5. How is the required containment capacity determined?

Containment systems are usually designed to hold:

• 100% of the transformer’s total oil volume,

• sometimes plus additional freeboard for rainwater or firefighting fluids.

Local regulations, site risk assessments, and authority requirements may define the exact sizing.

6. Are containment bunds part of transformer fire protection?

Yes. Bunds and containment basins are an important component of transformer fire mitigation. By retaining spilled oil, they:

• reduce pool fire formation,

• limit fire spread to adjacent equipment,

• support passive fire protection strategies.

Some systems are specifically designed to enhance oil fire suppression behavior.

7. Can containment systems replace concrete oil pits?

Yes. Modular steel bunds and prefabricated containment systems are widely used as alternatives to concrete pits. Advantages include:

• faster installation,

• reduced civil works,

• adaptability to existing substations,

• suitability for high groundwater or restricted sites.

8. Are temporary or mobile containment berms available?

Yes. Temporary containment berms or flexible oil spill berms are commonly used for:

• transformer maintenance,

• short-term storage,

• emergency response,

• commissioning and decommissioning works.

They offer rapid deployment without permanent foundations.

9. Can containment bunds be manufactured in custom sizes?

Absolutely. Custom-sized containment tanks or bunds are frequently required for:

• large high-voltage transformers,

• space-constrained substations,

• retrofit installations.

Tailored solutions ensure full oil retention while fitting existing layouts.

10. Are containment systems required for transformers in solar and renewable energy plants?

Yes. Transformer bunds for solar plants and renewable energy facilities are increasingly required, as oil-filled step-up transformers are commonly used in PV parks and wind farms. Environmental protection and permitting authorities often mandate secondary oil containment.

11. What materials are commonly used for transformer containment systems?

Typical materials include:

• coated structural steel,

• corrosion-resistant steel plates,

• integrated grating systems for load distribution.

Material selection depends on transformer weight, oil volume, and environmental exposure.

12. Who typically installs transformer oil bunds or containment tanks?

Transformer oil containment systems are installed by:

• utilities and grid operators,

• industrial plant operators,

• renewable energy project developers,

• substation and EPC contractors,

• operators of critical infrastructure.

They are a standard element of modern transformer safety and compliance concepts.