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Most power frequencies for GIS are 50 Hz originated in Europe and 60 Hz originated in North America. Apart from 16 ⅓ Hz and 25 Hz for railroad applications, the majority of GIS applications are with 50 and 60 Hz. These two frequencies are distributed world‐wide and form regions and countries with one or the other frequency. Some countries, for example, Japan and Saudi Arabia, have both frequencies.

The dielectric impact to the GIS design of these frequencies is negligibly low. The thermal impact needs to be considered when the current rating is approaching the limits, because at 60 Hz the power density is higher leading to higher thermal rise. Temperature limits should not be exceeded because of possible damage to insulators or contact systems.