Engineering and oil transformer risk management

Preventing Soil Contamination from Dielectric Oils

Oil Containment: A Regulatory and Environmental Requirement

Oil-filled transformers contain significant volumes of dielectric liquid, whether mineral oil or ester-based fluids. In case of leakage, these hydrocarbons can cause long-term soil and surface water contamination.

Regulations therefore require the implementation of watertight containment systems capable of retaining the full transformer oil volume, including under rainfall conditions.

SANERGRID® Oil Containment Solutions

SANERGRID® designs and supplies:

• Watertight transformer containment basins installed beneath transformers or as remote containment pits
• Modular systems adapted to large capacities and reduced installation time
• Drainage, isolation, control and monitoring accessories, including level sensors and alarm systems

These solutions:

• Prevent soil infiltration
• Reduce environmental remediation costs
• Ensure compliance with French and European environmental regulations, including ICPE compliance requirements and oversight by environmental authorities

Management of Rainwater Contaminated by Hydrocarbons

A Frequently Underestimated Risk

In outdoor installations, rainwater can accumulate in containment basins. If an oil leak occurs simultaneously, uncontrolled discharge may lead to off-site pollution. Overflow of oil-contaminated water is also a risk when basins become full.

Since electrical pumping systems may be unreliable or dependent on power supply, it is essential to ensure continuous drainage while controlling discharge quality. This guarantees permanent availability of containment volume in compliance with regulatory requirements.

This requirement is notably defined in international standards and guidelines such as:

• IEEE Std 979 and IEEE Std 980
• IEC standards
• CIGRE Technical Brochures (TB 406, TB 227, TB 209 depending on versions)
• European standard EN 61936-1
• French standards NF C 13-200 and NF C 17-100
• EU Water Framework Directive 2000/60/EC
• EN 858-1 standard for oil separators
• CNPP D9A Guide – Firewater containment systems

Controlled Rainwater Filtration and Discharge

SANERGRID® integrates high-performance hydrocarbon rainwater filtration systems that enable:

• Continuous discharge of clean water
• Filtration of hydrocarbon traces to ensure discharge below 5 ppm
• Immediate confinement and closure in case of oil detection
• Protection of drainage networks and natural environments
• Guaranteed retention capacity: the containment volume remains available for potential oil leaks, reducing overflow risk

These systems can be integrated into existing or new containment basins and are adapted to site flow rates using hydrophobic and oleophilic technologies from SPI Solidification Product International and its patented systems PETRO PIPE, PETRO PIT, PETRO BARRIER and PETRO PLUG.

Solutions operate autonomously without electrical power, by gravity flow, via pumping systems, or with intelligent communicating sensors such as MONITOFLOW®.

Reducing Transformer Fire Risk – Hydrocarbon Pool Fires

Understanding the Risk and Preventing Domino Effects

When dielectric oil spreads within a containment basin, it floats on the basin floor or on rainwater. In case of ignition, hydrocarbon fires develop exothermically and exponentially in both time and fire energy, producing a Class B fire — also known as a “hydrocarbon pool fire.”

Such fires are difficult to control and may rapidly spread to adjacent equipment either due to insufficient resistant containment structures or intense thermal radiation from flames and smoke (up to 1600 °C for mineral transformer oils).

Transformer Fire Barriers and Compartmentalization

SANERGRID® develops solutions to:

• Passively limit oxygen supply, slowing or naturally extinguishing combustion by suffocation
• Fragment the oil surface and contain it within a fire-resistant volume to prevent temperature escalation

These solutions include:

• Containment basins equipped with ERT and TRT fire barrier devices
• Fire-resistant cover systems and technical fire grating for concrete pits (EXTICOV CCF and EXTICOV LHD)
• Prefabricated remote containment pits DEPOSIT®, modern alternatives or complements to traditional gravel pits or recovery basins equipped with EXTICOV fire barrier devices, offering simplified maintenance

Fire-Fighting Water Management

Anticipating Emergency Situations

Fire-fighting water may be heavily contaminated with hydrocarbons and pollutants such as AFFF (Aqueous Film Forming Foam), extinguishing powders and foam agents used for Class B fires.

Uncontrolled discharge represents a major environmental risk and increasingly requires compliance with international and European standards, including:

• EU Water Framework Directive 2000/60/EC
• EN 858-1 oil separator standard
• CNPP D9A Guide – Firewater containment systems

Confinement and Treatment

SANERGRID® provides firewater management solutions through its DEPOSIT® range:

• Mechanical settling and oil-water separation using DEPOSIT® MV and MONITOFLOW® connected sensors
• Continuous rainwater filtration at DEPOSIT® MV outlet via DEPOSIT® SEPTA with innovative coalescence technology
• Temporary firewater containment via DEPOSIT® DW, capable of collecting water polluted by extinguishing agents with potential hydrocarbon presence, with optional intelligent MONITOFLOW® sensors
• Above-ground or underground firewater storage reservoirs DEPOSIT® RH2O, replacing fragile flexible tanks

These systems integrate into emergency response plans and local regulatory requirements.

Reducing Transformer Noise and Vibrations

A Key Issue for Acceptance and Durability – SANERVIB® Solutions

Transformers generate noise and vibrations due to magnetostriction and cooling auxiliaries. These phenomena can impact:

• Surrounding communities
• Building structures
• Component lifespan

Acoustic and Anti-Vibration Solutions

SANERGRID® implements the SANERVIB® range:

• Acoustic screens and enclosures
• Vibration isolation systems (mounts, mechanical interfaces)
• On-site diagnostics to precisely adapt solutions to frequency characteristics

In our industry, approximately 80% of perceived noise is linked to vibratory components rather than airborne sound, as transmission primarily occurs through structural elements.

SANERGRID® uses innovative and reliable solutions derived from the nuclear, railway and heavy industry sectors.

SANERVIB® systems exclusively use metallic steel materials, whose damping characteristics vary very little over time or temperature, ensuring long-term performance. These solutions reduce transformer noise — whether new or existing — without relying on flammable composites or polymers whose elasticity degrades over time.

A Comprehensive Approach by the SANERGRID® Group

The SANERGRID® Group relies on its complementary entities to deliver coherent transformer risk management:

• SANERGRID® – engineering and manufacturing of environmental and fire protection solutions
• SYNERDIS® – distribution of MV/HV transformers and equipment, including fire-enhanced cast resin dry-type transformers
• SONEC® – on-site services, installation and maintenance
• TECHNIKELEC® – e-commerce platform for accessories and technical spare parts

This organization supports operators from risk assessment to long-term maintenance, with solutions adapted to each site’s technical, regulatory and operational constraints.