Enhancement of Explosion-Proof Capability of On-Load Tap Changer Predicted by the Investigation of High-Energy Arc Characteristics Within the Oil Compartment

Severe arc faults and even fire accidents can be triggered by the failure of internal metallic insulation within on load tap-changers. Consequently, due to inherent limitations in testing capabilities and the associated safety hazards, systematic studies investigating arc voltage and pressure transients within on load tap-changers during actual arc fault events, as well as comprehensive assessments of their explosion-proof performance, remain relatively scarce in the existing literature. In view of this, this study first identifies the pressure relief device and top cover strength as critical factors for on-load tap-changers explosion protection, based on two preliminary arc fault tests. Subsequently, it investigates on-load tap changer explosion-proof strategies through computational fluid dynamics and explicit dynamic simulations. The results show that the reinforced top cover reduces the maximum displacement by 76.8% (from 1.83 mm to 0.42 mm) under impact. Finally, a prototype is manufactured and subjected to a high-energy arc fault test with an energy of 5.51 MJ, during which the peak internal oil pressure reaches 5.19 MPa without top cover rupture or fire ignition, validating the effectiveness of the proposed explosion-proof measures. This paper represents the first arc fault test conducted on an OLTC equipped with a diverter switch and provides valuable data for the study of arc characteristics within OLTCs under high-energy faults, and offers a reliable solution for OLTC explosion protection.