Surge Suppression Devices - Avoid transient voltage problems by understanding how to correctly apply Art. 285

摘要

In just milliseconds, a voltage surge can destroy valuable equipment or even bring an entire facility down; thus, protection against transient voltage spikes is important. Hard-wired transient protection devices are covered by either Art. 280 (above 1kV) or Art. 285 (1kV or less). Art. 280 refers to them as surge arresters, while Art. 285 calls them as surge-protective devices (SPDs). Most Art. 285 surge arresters operate by "clipping off" the highest level of voltage and diverting it away from the load. In this manner, the voltage on the conductor is limited to a predetermined level. The spark gap arrester is a simple device and an example of a surge arrester. Although it's an Art. 280 device, describing its operation helps us understand the operation of the surge arresters covered by Art. 285.