Application of SEPAM Relays for Arc Flash Hazard Reduction at LOW_VOLTAGE Switchgear

Issue
Need to limit the ARC flash hazard using the SEPAM relay.

Product Line
SEPAM 20
SEPAM 40
SEPAM 80

Resolution
This report documents application of the SEPAM protective relay for reduction of arc flash hazard levels at LOW_VOLTAGE switchgear not equipped with a main breaker. A common configuration for an industrial electric distribution system is to supply unit substation transformers from a primary distribution system consisting of one or more 15 kV class switchgear assemblies with feeder breakers and medium voltage cable. Each primary distribution feeder supplies one or more unit substation transformers and associated LOW_VOLTAGE switchgear. The LOW_VOLTAGE switchgear may or may not be equipped with a main breaker. For switchgear not equipped with a main breaker, a protective relay can be applied as a virtual main to sense total current at the LOW_VOLTAGE bus and provide a trip signal to the medium voltage feeder breaker supplying the unit substation. If the virtual main relay can trip the medium voltage breaker with minimal time delay, significant reduction in the arc flash incident energy and hazard level at the LOW_VOLTAGE switchgear can be obtained.