Aspects of arc-flash protection and prediction

• A big picture of arc-flash prevention and protection technologies has been given.
• Various arc-flash prediction technologies have been examined in order to develop proactive protection.
• The benefits of light and overcurrent based reactive arc-flash protection have been shown.
• The benefits and risks related to arc eliminators have been evaluated.
• IEC 61850 based communication in arc-flash protection systems has been discussed.

This paper provides a technological review of arc-flash protection of air insulated switchgear. It covers the whole range starting from switchgear design aspects until ultra-fast arc elimination. Special attention is paid to proactive technologies enabling preemptive detection of slowly developing faults. Various arc faults indicating phenomena are examined, and several sensor technologies for online monitoring are evaluated. Because preventive or predictive measures cannot totally eliminate the risk of arc faults, reactive protection by fast operating protection is justified. Two major reactive protection approaches are discussed: the current-limiting approach and the arcing time based approach. The benefits of protection based on simultaneous detection of light and overcurrent are explained. Finally the paper discusses arc elimination technologies and evaluates the concerns related to short-circuit devices.