9137200997 Rev D BE1-51 General Information 1-1
SECTION 1 • GENERAL INFORMATION
DESCRIPTION
BE1-51 Time Overcurrent Relays are microprocessor-based devices that monitor the magnitude of single-
phase, two-phase-and-neutral, or three-phase-and-neutral ac current to provide accurate time overcurrent
and instantaneous overcurrent protection for 50 hertz or 60 hertz power systems.
STANDARD FEATURES
Time Overcurrent Functions
Time overcurrent elements pick up over a range of 0.1 to 0.8 amperes, 0.3 to 2.4 amperes, 0.5 to 4.0
amperes, 1.5 to 12.0 amperes, 0.1 to 2.4 amperes, or 0.5 to 12.0 amperes and provide an adjustable time
delay that is proportional to the overcurrent. Time delay is initiated when the sensed current exceeds the
pickup point. When the current drops below the pickup point, the timing circuit is reset immediately. At
reset, the output contacts, if operated, are restored to normal.
Adjustment of the overcurrent pickup point is provided by controls on the relay front panel. Time delay is a
function of the characteristic curve that has been selected. Time delay is settable from 00 to 99 on the
TIME DIAL thumbwheel switch located on the front panel. Curve type is selected either as an option or, in
some models, is switch selectable.
Sixty-nine characteristic curves and three timing options are available. They are:
Characteristic curves:
• Seven inverse time
• Nine I
2
t
• Seven inverse time with extended timing range
• Nine I
2
t with extended timing range
• Five British Standard 142 (E curves)
• Seven integrating inverse time
• Nine integrating I
2
t
• Seven integrating inverse time with extended timing range
• Nine integrating I
2
t with extended timing range
Timing option Z1 (switch selectable - 16 position) B and C curves:
• Seven inverse time
• Nine I
2
t
Timing option Z1 with option 2-D or 2-E (switch selectable - 16 position) B and C curves:
• Seven inverse time with extended timing range
• Nine I
2
t with extended timing range
Timing option Z2 (switch selectable - 16 position) B and E (British Standard 142) curves:
• Seven inverse time
• One I
2
t
• Five British Standard (BS) 142 (E curves)
Timing option Z2 with option 2-D or 2-E (switch selectable - 16 position) B and E (BS142) curves:
• Seven inverse time with extended timing range
• One I
2
t with extended timing range
• Five British Standard 142 (E curves)
Timing option Z3 (switch selectable - 16 position) integrating B and C curves:
• Seven integrating inverse time
• Nine integrating I
2
t
Timing option Z3 with option 2-D or 2-E (switch selectable - 16 position) integrating extended B and C
curves:
• Seven integrating inverse time with extended timing range
• Nine integrating I
2
t with extended timing range
Courtesy of NationalSwitchgear.com
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