Measurements, observations and implications of moving electrical arc behavior and effect of reclosure events on overhead lines and worker protection

Characteristics of an electric arc in industrial and utility electrical equipment is dependent on many factors such as fault current level, duration of the arc, geometry of feeding conductors and electrodes, proximity of panels and other items affecting the direction or focus of the arc energy. The voltage rating of the system will affect the overall dimensions of conductor spacing which will result in higher released energy for the same fault conditions. Another factor of importance is the type of heat energy (predominately radiant or predominately convective). This can be generalized into four types: a) moving high heat flux arc in open air of overhead lines or substation buswork; b) stationary directional high heat flux arc in open air at the end of overhead line or substation buswork or transformer bushing; c) ejected directional high heat flux arc in enclosed medium voltage switchgear or cable splice failure; d) directional hot air exhaust from low heat flux arc in low voltage switchboards cabinets and motor control centers. Results of experimental testing for type (a) arc behavior and incident heat energy measurements of a moving and stationary open air arc are presented and discussed. Work practices for mitigating effect of electric arc are recommended for overhead lines.