Analysis of the Power Cable Fire Case in Busan-JungKwan Energy

In this paper, the fire cause of blackout occurred in the Busan-JungKwan Energy as a Community Energy System (CES) was analyzed. Through analysis of the data such as burn patterns at the site, melted shape of cable head by the fire, overcurrent relay (OCR) of the control system, and event log, it was confirmed that first ground fault occurred at the termination connection of secondary cable of transformer. It was concluded because the void space of insulation and electrical melting trace conductor were investigated in the cable stress cone by detailed investigation and X-ray inspection for cable termination. In addition, as the damage by the tool on the vertical direction to the conductor was identified, it was presumed that the accident occurred by deterioration progress of insulation which was accelerated than that of the other parts.

Optimization of electroslag melting towards to titanium morphology improvement in combined Kroll process

Purpose The paper aims to optimize calcium difluoride electrical melting process towards creating titanium production with improved morphology by combining titanium reduction and electroslag melting processes. The study aims to explore optimal electrical heating power in the slag supplied via tungsten electrode and formation of a stable skull layer on water-cooled walls of a cylindrical stainless steel reactor, which is crucial for electroslag melting. Design/methodology/approach The multi-physical numerical modelling approach using commercial software COMSOL Multiphysics is presented in the paper by coupling electrical, heat transfer and fluid flow problems. The slag material phase change and corresponding changes of physical properties such as electrical conductivity and viscosity are modelled by step function, sharply changing value of parameter near the phase change temperature. A parametric study of applied electrical power has been carried out to find optimal conditions for the skull-layer formation. Findings The paper provides an estimation of necessary electrical power to avoid overheating or solidification of the top layer of slag, which is unacceptable for the combined Kroll process. The study also revealed important poloidal buoyancy flow with characteristic velocity of few cm/s of in the reactor, which governs the heat transfer process and formation of the skull layer. Research limitations/implications The presented simplification in numerical model offers high calculation speed but lacks fully developed phase change model, e.g. excluding latent heat. Also, heat transfer through radiation is neglected in the model. Originality/value The paper presents an original way to overcome the complexity of modelling slag electrical melting/solidification phenomena using temperature-dependent properties with step functions.