The Importance of Bunding for Transformers: Safeguarding Environment and Safety


Transformers play a crucial role in the transmission and distribution of electrical power, serving as vital components in power grids worldwide. These devices often contain insulating oil, which facilitates efficient operation but also poses environmental and safety risks if not properly managed. One essential measure for mitigating these risks is bunding - the practice of placing secondary containment systems around transformers

Understanding Transformers and Insulating Oil:

Before delving into bunding, it's essential to grasp the basics of transformers and the role of insulating oil. Transformers are devices that transfer electrical energy from one circuit to another through electromagnetic induction. They come in various types and sizes, ranging from small distribution transformers to large power transformers used in electrical substations.

Insulating oil, commonly referred to as transformer oil, serves several critical functions within transformers. It acts as both an electrical insulator and a coolant, allowing the transformer to operate efficiently while dissipating heat generated during operation. Traditionally, mineral oil has been the most commonly used insulating oil due to its excellent dielectric properties and cooling capabilities.

Environmental and Safety Risks Associated with Transformers:

Despite their importance in power distribution, transformers pose environmental and safety risks, primarily due to the presence of insulating oil. The potential hazards associated with transformers include:

Oil Leaks and Spills: Over time, transformers may develop leaks or experience spills due to various factors such as aging, mechanical failures, or external damage. These incidents can result in the release of insulating oil into the surrounding environment, leading to soil and water contamination.

Fire Hazards: Insulating oil is combustible, making transformers susceptible to fire hazards, particularly in the event of electrical faults or overheating. A fire involving transformer oil can have severe consequences, posing risks to nearby infrastructure, property, and human safety.

Environmental Impact: The environmental impact of transformer oil spills extends beyond immediate contamination. Oil leakage can harm ecosystems, disrupt wildlife habitats, and contaminate water sources, posing long-term ecological risks.

Oil can also escape as a result of copper theft from transformers (below). In this case where there was no bunding, oil escapd into River Stour and was found flowing for over three miles.
This environmental damage could have been prevented.
According to BS EN 61936‑1:2021 section, transformers containing more than 1,000 litres of insulating liquid must be bunded.

copper theft from transformer
Copper theft from transformer

Importance of Bunding for Transformers:

Bunding serves as a critical preventive measure to address the environmental and safety risks associated with transformers. Here's why bunding is essential:

Containment of Oil Spills:

The primary purpose of bunding is to contain any oil leaks or spills that may occur during the operation or maintenance of transformers. By providing secondary containment around the transformer, bunding prevents the spread of oil and minimizes the risk of environmental contamination. In the event of a leak, the bunded area acts as a barrier, containing the oil and preventing it from seeping into the surrounding soil or waterways.

Environmental Protection:

Bunding plays a crucial role in protecting the environment from the adverse effects of transformer oil spills. By confining oil within the bunded area, the risk of contamination to soil, groundwater, and surface water bodies is significantly reduced. This proactive approach helps preserve ecosystems, prevent ecological damage, and safeguard natural resources for future generations.

Compliance with Regulations:

There are regulations and standards in place that require the bunding of transformers as part of environmental protection and safety measures. Compliance with these regulations is essential for utility companies, industrial facilities, and other entities responsible for the operation and maintenance of transformers. By implementing bunding solutions, organisations demonstrate their commitment to regulatory compliance and responsible environmental stewardship.

Risk Mitigation:

Bunding serves as a proactive risk mitigation measure, reducing the likelihood and severity of environmental incidents involving transformers. By containing oil spills within the bunded area, the potential impact on surrounding areas is minimised, mitigating the risk of costly clean-up efforts, legal liabilities, and reputational damage. Bunding helps organisations mitigate risks associated with transformer operation, enhancing overall safety and reliability.

Types of Bunding Systems:

Bunding systems for transformers vary depending on factors such as transformer size, location, and regulatory requirements. Common types of bunding systems include:

Concrete Containment Berms: Concrete containment berms are constructed around transformers to create a durable and impermeable barrier for containing oil spills. These berms are typically designed to withstand the weight of the transformer and any accumulated oil, providing robust secondary containment.

Steel Bunding Walls: Steel bunding walls consist of prefabricated steel panels assembled to enclose the transformer and create a bunded area. These walls offer flexibility in design and installation, making them suitable for various transformer configurations and site conditions.

Earthen Bunds: Earthen bunds involve excavating and shaping the terrain around the transformer to create a natural containment area for oil spills. These bunds are often lined with impermeable materials such as geomembranes to prevent oil seepage into the soil.

Portable Containment Systems: Portable containment systems, such as flexible berms or inflatable barriers, offer temporary secondary containment for transformers during maintenance activities or temporary installations. These systems can be easily deployed and removed as needed, providing flexibility and convenience.

Best Practices for Bunding:

To ensure the effectiveness of bunding systems for transformers, it's essential to adhere to best practices and guidelines. Some key considerations include:

Proper Sizing: Bunding systems should be appropriately sized to accommodate the maximum volume of oil that could potentially be released from the transformer. Adequate capacity ensures that the bunded area can contain oil spills without overflow or breach.

Regular Inspection and Maintenance: Routine inspection and maintenance of bunding systems are essential to identify any damage, deterioration, or signs of leakage promptly. Regular upkeep ensures that bunding remains intact and fully functional, minimising the risk of containment failures.

Emergency Response Preparedness: Organisations should have robust emergency response plans in place to address oil spills or leaks from transformers promptly. Training personnel, maintaining spill response equipment, and coordinating with relevant authorities are critical components of effective emergency preparedness.

Environmental Monitoring: Implementing environmental monitoring measures, such as soil and water sampling, can help detect and assess the extent of contamination in the event of an oil spill. Monitoring data informs decision-making regarding remediation efforts and environmental restoration.


Bunding plays a vital role in protecting the environment and ensuring the safety of transformers by containing oil spills and minimising their impact. By implementing robust bunding systems and adhering to best practices, organisations can mitigate environmental risks, comply with regulations, and enhance overall operational resilience. As transformers continue to play a central role in global energy infrastructure, proactive measures such as bunding are essential for sustainable and responsible operation.