V. EXPERIMENTATION WITH MV/LV TRANSFORMERS
A. Transformers and testing
Standard distribution transformers provided by four manufacturers
were filled in factory with the low-viscosity ester
composition. All of them are fulfilled non-breathing
transformers, viz. so sealed that there can be no significant
interchange between its contents and the external atmosphere
(no O2 and moisture ingress), and filled so that there is no
cushion of air inside the tank (which has to cope the thermal
expansion of the fluid). The cooling mode of these transformers
is ONAN type, which means that there is no fan or pump, and
that the insulating liquid circulates only by thermosiphon inside
the tank.
0 m.