Alejandro

Dielectric strength is commonly measured using a BDV test set with standardized electrodes and a controlled voltage ramp until breakdown occurs. Lab grade units control electrode gap, rise rate, sample stirring, and temperature more precisely, while field kits provide quick screening. Supporting equipment may include sample containers, cleaning tools for electrodes, and moisture measurement instruments, because water strongly affects BDV. For comprehensive assessment, dielectric loss factor and resistivity instruments are also used alongside BDV testing.

A breakdown tester applies an increasing AC voltage across two electrodes immersed in a standardized oil sample until electrical breakdown occurs. The breakdown voltage is recorded, often repeated multiple times on the same sample to obtain an average and to reduce random variability. The test is highly sensitive to moisture, fibers, carbon particles, and bubbles, so sample handling and cleaning of the test cell matter a lot. IEC 60156 is a common reference method, specifying electrode geometry, gap, stirring conditions, and voltage rise rate.

Filtration is required when condition monitoring shows elevated moisture, reduced breakdown voltage, rising acidity, increasing particle count, or poor dielectric dissipation factor. It is also applied after repairs, after oil handling or topping up, following alarms related to Buchholz or pressure relief, or when leaks introduce air and moisture. Filtration is common during planned maintenance outages, and in critical assets it may be performed online using dedicated systems that treat oil without de energizing the transformer.

Most transformer oils are refined hydrocarbons, mainly paraffinic and naphthenic mineral oil fractions, sometimes with aromatic content kept within limits. Many products include oxidation inhibitors such as DBPC, metal passivators to reduce corrosive sulfur effects, and antifoam agents. Natural and synthetic ester oils are based on ester molecules rather than mineral hydrocarbons. Silicone transformer fluids are based on polydimethylsiloxane polymers. Exact composition is typically described as proprietary in SDS, but the chemical family and additive function are disclosed.