Distribution switchgear is typically mounted on power poles, in wet or dry vaults, or in padmounted switchgear enclosures, and is used with overhead and underground electric utility distribution lines. The evolution of distribution device controls from hydraulic and the electro-mechanical to microprocessor-based has also led to the controls being mounted on power poles, in padmounted switchgear, and in vaults. These locations expose the microprocessor-based controls to the harsh environmental, mechanical and electrical conditions of the electric utility distribution lines. The apparatus used for overhead pole applications and for padmounted applications is typically subject to adverse environmental conditions, such as high winds, potentially heavy precipitation, high solar radiation levels, and extreme ambient temperatures (very high and very low). Furthermore, these installations may be exposed to extreme voltage disturbances, both due to lightning surges in areas of high lightning activity and from switching surges. Apparatus used for vault applications are typically subject to moisture (and possibly submersion); users must address the difficulty in locating and connecting the control, protecting the control cables and connections, and in providing adequate grounding. These installations may have marginal (or no) auxiliary voltage supply and may be subject to extended durations of voltages below the normal operating range. This standard offers design, testing, and application measures, that are appropriate to the special conditions of use of microprocessor-based controls devices. The intent of these measures is to improve the reliability and extend the life of the controls.