Arcing Horns

Arcing horns are used in several countries to provide a path for the power-frequency flashover arc that is off the insulator surfaces. A recent OGRE paper de Tourreil and Schmuck 2009) provides a comprehensive summary of the application of devices for power are protection of transmission line insula­tors. Most applications are presently made across ceramic insulators, but arcing horns are also recommended as a way to take power-follow current off the vulnerable end fitting interfaces of polymer insulators. In cases where there may be many contamination, icing, or lightning flashovers, it may be prudent to fit arcing horns in order to protect the mechanical integrity of the insulators as a mitigation option.

Chino et al. [2005] reported the development of a current-limiting arcing horn for 77-kV systems. In addition lo protecting the insulators from power-arc damage, an ablative material in the interruption portion pro­vides gas that cools and quenches the power arc in a half-cycle of ac. prevent­ing recognition. This means that the power quality disturbance from any contamination flashovers can possibly be mitigated without a circuit breaker operation.

The current-limiting arcing horn was designed mainly to function for light­ning impulse flashovers, and its use for mitigating contamination flashovers after the fact should be explored in future research. There are other important reasons to evaluate the use of arcing horns in contaminated areas. In areas of high contamination, it is common to retrofit distribution or sub-transmission lines with insulators that have greatly increased leakage distance, or to add more disks to the strings of transmission lines. This increases the dry arc distance as well. If too many disks are added, there is a possibility of poor coordination with terminal equipment—for example, exceeding the rated BIL of circuit breakers. Since surge arresters carry their own risks of flashover, puncture, and thermal runaway in heavy contamination conditions, the use of rod gaps or arcing horns on station insulators may be a better choice in some cases to limit incoming surge voltages.

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