scope:

This standard presents basic requirements for the design, testing and application of microprocessor-based controls of distribution switchgear rated above 1 kV and up to and including 38 kV. The standard is intended to mitigate the effects of the harsh environments that may be encountered outside the protections provided by a typical substation. This standard applies to microprocessor-based devices employed in distribution switchgear typically mounted on power poles, in wet or dry vaults, or in pad-mounted switchgear enclosures. This standard does not apply to microprocessor-based devices employed in high voltage circuit breakers (IEEE Std C37.04™ "Standard for Ratings and Requirements for AC High-Voltage Circuit Breakers with Rated Maximum Voltage Above 1000 V") or metal-enclosed switchgear (IEEE Std C37.20.2™ "Standard for Metal-Clad Switchgear" and IEEE Std C37.20.3™ "Standard for Metal-Enclosed Interrupter Switchgear (1 kV-38 kV)"). This standard does not invalidate any tests performed on power system protective relays which are designed to IEEE Std C37.90™ ("Standard for Relays and Relay Systems Associated with Electric Power Apparatus"). Lastly, this standard does not cover the design of the control enclosure such as mounting, latching, or user accessibility, and does not supersede the requirements of controls which are defined and tested per the switchgear equipment standard.

Purpose

Distribution switchgear is typically mounted on power poles, in wet or dry vaults, or in pad-mounted enclosures and is used with overhead or 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 pad-mounted 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 and pad-mounted applications are typically subject to potentially adverse environmental conditions, such as high winds, heavy precipitation, high solar radiation levels, and both high and low extreme ambient temperatures. These installations may also be exposed to extreme voltage disturbances from lightning and switching surges. Apparatus used for vault applications are typically subject to moisture (and possibly submersion); users may encounter 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 the use of microprocessor-based control devices. The intent of these measures is to improve the reliability and extend the life of the controls.