The volume of CO+CO2 formed stands for the value obtained when the cellulose-based materials are heated up at a similar temperature [17].
However, in a real transformer all these materials cannot be heated up at a similar temperature.
According to the designing data from SC ELECTROPUTERE SA CRAIOVA the mean temperature of
a transformer’s winding must range below the value of 85°C and the maximum value has to range below 95°C.
The greatest part of the insulating paper reaches the temperature of 85°C and only asmall part of paper reaches the temperature of 95°C, the latter one representing about 10% of the total of paper.
This temperature is to be constant after putting the transformer to operation.
The volume of CO+CO2 produced by the transformer cardboard can come from two sources: the first one is made up of the cardboards between windings and the second one made
up of the rest of cardboards.
The cardboards between windings reach temperatures of 70°C and 75°C and the rest of cardboards reach the temperature of 50°C.
The cardboards between windings represent about 10% of the total of cardboards.
In table 2 there are presented the quantities of paper, cardboards and the temperatures they can reach for a transformer of 250 MVA (data taken from SC ELECTROPUTERE SA CRAIOVA and [16], [17]), the proportions in which these materials exist (total 1) as well as the speeds for formation of gases studied carbon monoxide and dioxide), calculated with the relation 5.