Oil-immersed inverted current transformers exhibit high-level destructive characteristics during arc flash explosions

with fragments ejected over a wide area at high velocity

posing a significant impact threat to surrounding equipment and personnel safety. However

IEC 61869-1/IEEE C57.13.5 merely outlines the fundamental framework for arc testing of instrument transformers. Core aspects such as arc parameters and evaluation criteria remain un-standardized

leading to divergent testing methodologies and non-comparable results. This hinders the development and refinement of a comprehensive arc testing system for current transformers. Consequently

we established a systematic testing protocol encompassing ‘arc initiation and containment-protective systems-circuit configuration-explosion criteria'. We analyzed the dynamic progression of arc flash explosions in current transformers. Exploratory optimizations of structural elements

including explosion vent discs and vent pathways-target conventional weak points in the core assembly

were performed. A series of comparative arc flash tests were subsequently conducted to validate these modifications. Test results indicate that the arc flash explosion process in current transformers comprises four distinct phases: sudden pressure rise

pressure accumulation

tearing

and explosion. Reasonably adjusting the burst disc threshold and the size of the oil tank connection channel can significantly reduce the energy release level. The modified current transformer demonstrates a 48.4% reduction in the fragmentation scatter range

with the kinetic energy of fragments restricted below 76 J/cm². The experimental methodology provides a reference for establishing arc-burning test standards

while the results furnish theoretical support for enhancing the explosion-proof performance of current transformers.