Transformer Protector

The TP is activated within 0.5 to 20 milliseconds, depending on arc location and transformer size, by the first dynamic pressure peak of the shock wave, avoiding transformer explosions before static pressure increases.

  • Eliminates Costly Plant Outages
  • Prevents Fire Damage to the Transformer and Surrounding Equipment
  • Prevents Environmental Pollution by Containing the Oil
  • Eliminates Risk to Human Life
  • Saves Company Reputation

Why Transformers Explode

The Phenomenon

During a transformer short-circuit, the electrical arc vaporizes oil and creates a Dynamic Pressure Peak which travels at the speed of 1,200 meters per second (4,000 feet per second). This phenomenon occurs within a few milliseconds. Because of reflections in the tank the pressure peak will generate pressure waves. The integration of all of the waves pressure peaks creates static pressure. Then, the pressure becomes equal throughout the entire transformer tank within 50 to 100 milliseconds after the electrical arc, and causes the transformer tank to rupture.

Lack of International Transformer Standards And Regulations

Transformers can only withstand a small overpressure and are not designed as pressure vessels according to ASME Codes and Controls. Consequently, transformers have proven to be very dangerous. Because transformer standards describe electrical requirements but do not cover mechanical design.

Transformer Electrical And Mechanical Protection Limits

  • Pressure Relief Valve inadequacy: Pressure Relief Valves are suitable for slow pressure rise whereas pressure gradients developed during low impedance faults are extremely fast. Transformers that have exploded were usually equipped with Pressure Relief Valves.
  • Buchholz and Rapid Pressure Relay inefficiency: transformer electrical protections are not designed to react to sharp pressure gradients. During the 62 TRANSFORMER PROTECTOR tests, the Buchholz always failed to detect any gas and oil movement or pressure variation.
  • Electrical Breaker opening time: the best breaker technology trips in 50 milliseconds, far too late to prevent the explosion because most of the gases are generated within milliseconds after short-circuit. Consequently, the tank pressure keeps increasing even after the breaker has opened.

How Transformer Protector Works

Transformer Protector Operation

  • The TRANSFORMER PROTECTOR activates within milliseconds depressurizing the transformer main tank.
  • Once the depressurization is complete, to avoid the bazooka effect from killing maintenance technicians during tank opening, the transformer is then injected with inert gas to evacuate the remaining explosive gases.
  • After the explosive gases have been cleared, the transformer is then safe and ready for repair.

The TRANSFORMER PROTECTOR is the only proven solution to transformer explosion and fire. 20 years of extensive high-level mechanical research and tests were necessary to design the TRANSFORMER PROTECTOR.

The TRANSFORMER PROTECTOR is a transformer explosion and fire prevention system suitable for any type of oil-immersed transformer and including surrounding equipment such as the On Load Tap Changer (OLTC), Oil Cable Box (OCB), and Oil Bushing Cable Box (OBCB).

Transformer Protector Components

Client Installations

Since 2005, the TRANSFORMER PROTECTOR has been included in the technical specifications of 171 companies in 65 countries. It currently protects thousands of transformers manufactured by 175 different transformer manufacturers and has also achieved the following:

  • Thousands of TPs sold worldwide
  • CEPEL, Brazil, one of the world’s top High Voltage laboratories has performed 34 successful live tests on three different large transformers
  • Electricity De France (EDF), High Voltage Laboratory has performed 28 successful live tests on a small transformer
  • Power-Gen Europe – Best Paper Award 2008

The NFPA recommends Fast Depressurization Systems for all Power Plant and Substation transformers the following Civil Codes which the TRANSFORMER PROTECTOR (TP) complies with:

  • NFPA 850 (Recommended Practice for Fire Protection for Electric Generating Plants, High Voltage Direct Current Converter Stations and Fire Protection for Hydroelectric Generating Plants)

Research & Test

Since 1999, our Research Department has released 59 scientific articles about transformer short-circuit calculations, tests, mathematical models, simulations and TRANSFORMER PROTECTOR efficiency to avoid transformer tank explosions and oil fires (list available upon request).

In order to study the energetic transfer phenomenon that occurs during a short circuit in transformers 2 experimental test campaigns were carried out; the first by Electricité de France in 2002 and the second by the Brazilian high voltage laboratory CEPEL, in 2004 on large scale transformers.

These 62 experimental tests consisted in creating low impedance faults in oil filled transformers equipped with the TRANSFORMER PROTECTOR. The tests showed that the arc first creates a huge volume of gas that is quickly pressurized, generating one high pressure peak that propagates through the oil. This First Dynamic Pressure Peak activates the TP within milliseconds preventing the transformer from exploding.

In addition to the experiments, a compressible two-phase flow numerical simulation tool has been developed. The experimental results have been used to validate the simulation model. Adding to this model a dynamic structural analysis package has been coupled to create a fluid structure interaction. These simulations definitively show the efficiency of the TRANSFORMER PROTECTOR to prevent explosion and fire.

The arc used in the simulation, located at the base of the right bushing, has parameters given in the table below and total energy of 7.19 MJ.

Current(Peak) Voltage (Peak) Frequency Duration Total Energy
2,000 A 80,000 V 50.0 Hz 0.110 s 7.1986 MJ



Financial Benefit

A Growing Concern For Corporate Risk Managers And Insurance Companies

Transformers are considered by Corporate Risk Managers and Insurers as the most critical equipment inside plants because of the large quantity of oil in contact with high voltage elements.

Damage Cost Of Transformer Explosion And Fire

The cost to replace a transformer unit is several million dollars (USD) and the cost of the outage in the tens of millions (USD) with potential to reach hundreds of millions (USD). Transformer explosions and fire result in: lost income, purchase of high-priced replacement power, replacement of transformers and surrounding equipment, polluting the environment and negative public relations, etc.

The damage caused depends on the transformer location:

  • Power plant incidents result in very high loss of revenue and can lead to company bankruptcies if not insured. For insurers, the projected cost reference can approach USD 500,000 per MVA.
  • Transmission substation incidents can result in the complete blackout of a region or a country. Several well-known cases have been recorded recently (USA, UK, Italy, Spain, etc.).
  • Distribution transformer explosions in urban areas can have disastrous financial consequences in related pollution and litigation costs.

Purchasing The Transformer Protector

The TRANSFORMER PROTECTOR comes with a liability insurance policy with coverage up to 15 million EUR per occurrence should an incident occur.

Equipping your transformers with the TRANSFORMER PROTECTOR:

  • Decreases the risk to surrounding equipment and buildings.
  • Enables the quick internal repair of the transformer and sharply reduces plant outages.
  • Leaves the environment unharmed.

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