Optimal Design of a Follow Current Disconnector for DC Arresters in Traction Vehicles

The safety and reliability of electric traction vehicles are seriously endangered by external lightning strokes and internal switching surges which result from the operation of circuit breakers or the moving contact between the pantograph and the overhead catenary wire. Overvoltages in electric traction vehicles are much higher than the rated voltages of railway system, causing server damage to the insulation of electrical equipment and resulting in personal injury. A metal-oxide surge arrester, which has the advantages of non-linear voltage-current (V-I) characteristic, fast response, and large energy absorption capability, is usually connected in parallel with the equipment or the overhead line to protect them from overvoltages [1,2]. However, the arrester ages gradually when subject to defects during manufacture, moisture ingress, and excessive surge current. If the deteriorated arrester is not removed, thermal runaway may occur owing to the increase in leakage current, even at rated stress, leading to a line-to-ground fault and consequent electrical hazards [3-6]. Figure 1 shows a photograph of an arrester failure, leading to Guoming Wang, Sun-Jae Kim, Seo-Jun Park, and Gyung-Suk Kil Department of Electrical and Electronics Engineering, Korea Maritime and Ocean University, Busan 49112, Korea