Due to high humidity

heavy contamination

and low insulation margins during operation

epoxy-resin-cast insulated post-type current transformers used in 40.5 kV indoor switchgear are prone to aging within designed service life

resulting in surface insulation failure and posing a significant threat to the safety of the power system. Current research on the aging and failure mechanisms of epoxy resin current transformers under actual harsh operating environments remains insufficient. Consequently

tests were performed on unaged and aged insulation materials of current transformers. From a microscopic perspective

the differences in performance

morphology

and molecular structure between the upper and lower surfaces of the materials before and after aging were analyzed. The results indicate that the upper surfaces of the insulating material of current transformers experience significantly more severe aging than the lower surfaces. After aging

the surface resistance and partial discharge inception voltage decreased by up to 99.94% and 68.80%

respectively. Soluble surface contaminants primarily consisted of Ca2+

NO3−

SO42−

and Cl−. Aging causes the material surface to become loose and uneven

with surface roughness increasing by 100% to 200%

accompanied by the formation of cracks

pits

and pores

while the static contact angle decreased by up to 36.9%. The aging and failure mechanisms of the current transformer insulation material in high-humidity and heavy-contamination environments primarily include: moisture causes swelling and structural defects in the composite material; inorganic salts in the contamination corrode the material and exacerbate moisture-induced aging; leakage currents and partial discharges damage the molecular structure; aging byproducts such as alcohols and carboxylic acids reduce surface hydrophobicity; and high-energy discharges carbonize the organic material

further accelerating overall insulation failure.