X-wax formation in transformer liquid dielectrics

Transformer wax (x-wax) formation in dielectric oil under electric stress is demonstrated in the laboratory scale. The x-wax is found to be insoluble and influences the oil-impedance characteristics significantly. The variation of oil-impedance as a function of electric stress exposure time revealed a unique transition in the oil-impedance. Initially, the impedance decreases with electric stress exposure time and at a threshold time the impedance increases. The transition point of impedance is attributed to the x-wax formation. These results are substantiated with the FTIR and microscopic analysis of the oil samples. The effect of temperature and moisture on the x-wax formation is studied. Besides, the study is extended to understand the role of copper and uncured resin on x-wax formation. The temperature is found to have more influence on the x-wax formation compared to moisture, copper and uncured resins.