Funkenüberschlags

Funkenüberschlag, commonly translated as sparkover, refers to the electrical discharge that bridges an insulating gap between conductors or from a conductor to a grounded surface when the applied voltage exceeds the dielectric strength of the medium, typically air. In electrical engineering, sparkover is a form of dielectric breakdown and is a critical consideration in the design of insulators, switchgear, and high‑voltage equipment. The phenomenon can occur across air gaps, through defects in solid insulation, or along contaminated or moist surfaces, and it is closely related to related processes such as tracking and arcing.

Causes and mechanisms include an insufficient air or creepage distance, high electric field concentration around sharp edges or points, surface contamination (dust, salt, oil), humidity or rain, and aging or defects in insulation. The breakdown process starts with local ionization in the medium, which can propagate rapidly to form an arc or spark that conducts substantial current. The exact voltage at which sparkover occurs depends on gap length, pressure, temperature, humidity, contamination, and the geometry of the conductive paths. In air, the phenomenon is often described in terms of breakdown voltage for a given gap and conditions.

Testing and standards address sparkover voltages for components such as insulators and switchgear. Sparkover voltage tests are performed under controlled atmospheric conditions to determine the voltage at which an unintended arc forms. Standards from international and national bodies specify test methods, specimen preparation, and acceptance criteria, enabling comparisons across products and feeds into design margins.

Mitigation focuses on increasing the clearance and creepage distances, ensuring clean and dry surfaces, using insulating materials with adequate dielectric strength, applying coatings or barriers to reduce field concentration, and incorporating protective design features such as barriers, gland seals, or surge protection. Proper maintenance and environmental control are also important to minimize the risk of sparkover and related damage.