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Arc-Flash Mitigation Through Use of Voltage Controlled/Voltage Restrained Overcurrent Elements Arc-Flash Mitigation Through Use of
Voltage Controlled/Voltage Restrained
Overcurrent Elements

Abstract: This paper investigates the use of voltage controlled/voltage restrained overcurrent elements as
an arc-flash mitigation technique when applied to certain industrial circuits. The voltage
controlled/voltage restrained overcurrent elements can be used to provide fast and selective clearing of
faults on circuits feeding transformers and individual loads. Comparisons are made between
conventional overcurrent and voltage controlled/voltage restrained overcurrent in coordinated clearing
speeds and the reductions in arc-flash energy, as well as the corresponding reductions in personal
protective equipment (PPE) necessary for work around the circuits. Guidelines are provided for selecting
and setting the elements.

Conventional practice in industrial facilities has medium voltage radial feeders supplying transformers of
unit substations, with protection provided by time overcurrent elements coordinated with time
overcurrent elements on the secondary of the transformer. This time coordination means that faults on
the medium voltage feeder or in the primary winding of the transformer will be allowed to persist for an
extended period to allow the downstream devices an opportunity to trip. This paper will show that these
high side faults can be detected and selectively cleared without the need to wait for the secondary
overcurrent devices to time out.

Presenting (lead) author:
David Beach
Senior Application Engineer
Basler Electric Company
707 SW Florence
Gresham, OR 97080
Phone 503/465-8013
Fax 503/465-8038
email:
davidbeach@basler.com


Co-author:
Gerald (Jerry) Johnson
Senior Application Engineer
Basler Electric Company
11502 Allecingie Parkway
Richmond, VA 23235
Phone 804/897-8700
Fax 804/897-8707
email: geraldjohnson@basler.com