Interview with Arnaud Magnier, Vice President at SERGI Transformer Protector



SERGI has its headquarters in France, near Paris. As of today, it is a company of more than 100 employees worldwide, operating two entities in France, one in India, one in Brazil, USA of course, and Peru. SERGI has two manufacturing facilities, one in France and the other in the USA. The U.S. facility was established because of the large SERGI customer base in USA and Mexico. SERGI sells approximately 400 TRANSFORMER PROTECTOR (TP) units per year, averaged over the past three years.



A long journey to the ultimate safety

SERGI was created in the 1950s by Electricité de France (EDF), the French owned electricity generation, transmission and distribution company, which needed a solution for extinguishing fires caused by transformer explosions. At that time, SERGI used to design and manufacture a system called “Drain and Stir” to extinguish transformer fires.

In the beginning of the 1990s, the company decided to invest in preventive technologies to prevent transformer explosions, and thus avoid oil fires. SERGI was a small business of around ten employees then and only few people were dedicated to manufacturing the “Drain and Stir” fire extinguishing system, while the remaining staff were mainly researchers. This solely explains the strong, permanent, outstanding and up-to-date SERGI policy in R&D investments.

In line with this new approach, SERGI started conducting an intensive R&D program in 1995, which led to the first TRANSFORMER PROTECTOR (TP) patent application in 1999, and the first TP on-site installation was done in Italy one year later.


In France, EDF implemented the TP for the first time in 2007.


Abundance of simulations and prototyping

To first explain the phenomenon, transformers explode primarily because of internal electrical arcs resulting from failure of electrical insulation. When occurring, electrical arcs immediately generate a large gas volume in the sealed transformer tank. These gases produce a first dynamic pressure peak reflecting inside the tank, creating pressure waves. Within milliseconds, the pressure waves superimpose to create static pressure, meaning that pressures become uniformly applied on the entire tank leading to explosion and fire.


Since 1995 SERGI has been developing its own numerical solvers to simulate the behavior and properties of electrical arcs, the associated gas generation inside transformer oil, first dynamic pressure peak propagation, pressure wave creation and static pressure build-up inside transformer tanks. These investigations allowed SERGI to understand the transformer explosion phenomenon and design the TP to be activated, depending on arc location and transformer size, within 0.5 to 20 milliseconds by the first dynamic pressure peak to avoid transformer explosion before the static pressure increases.