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Oil Transformer risk management : how to protect your electrical installations ?

A- For the medium and low voltage and distribution domains 

1.A single retention tank is mandatory and must contain at least 100% of the volume of the dielectric oil contained in the transformer. (BDRSA, BDRG2, TRT and TRFLEX) in UK it must be minimum 120%

2.You can also use an extinguishing retention tank equipped with a fast dielectric extinguishing system made of slats. Generally, for oil volume upper than 600 litres it is recommended. (ERT and ERT MODULO). This system is a good compromise to avoid the classical stones or pebbles into retention pit and has been tested in independent labs
 

3.In the event of exposure to rainwater, every precaution must be taken to ensure that the retention tanks or pits do not fill with water or that it is evacuated properly. (SPI, PETRO PIT, PETRO PIPE, PETRO BARRIER, PETRO PLUG)

4.You can avoid oil using a Cast resin transformer, equipped with thermal probes to protect them against overheating by automatically switching off. You can also use higher temperature dielectric oils such as Ester (natural or synthetics) or silicone oil. (TrafoELETTRO and SGB)

B-For power domains and high voltage

1.Around 40 MVA, the oil quantity starts to be too big just to retain and extinguish at the same place. Due to this it is recommended by international standards that transformer must be equipped with a pit or a recovery tank that must have a minimum capacity of 20% of the transformer's quantity of liquid and must be equipped with a rapid and natural extinguishing device dielectric ... (EXTICOV and LHD instead of stones and pebbles)

2. ... this recovery tank must be connected to a separate recovery tank or interceptor (remote pit) of capacity at least equal to that of the transformer of the highest volume (in case of various transformers connected), when common to several transformers. (DEPOSIT)

3.The transformer must be installed at a safe distance from the building. When the safety distance cannot be maintained, a fire-resistant wall shall be implemented in accordance with the provisions described in the standard of each country. (CERBERO)

As every country has its legislation and regulations, do not hesitate to contact our SANERGRID experts so that we can advise you in the most effective way and adjusted to your territory