1-2
BE1-51 General Information
9137200997 Rev D
Characteristic curves are shown by the graphs in Appendix A,
Time Overcurrent Characteristic Curves.
Note that each graph (i.e. function) consists of a set of representative curves. Each curve (as well as any
between-curve interpolation) is selectable by the front panel
TIME DIAL
using a two-digit destination from
00 to 99. Because of space limitations, each graph shows only 14 of the 100 possible selections.
Non-Integrating Timing
Timing options Z1 and Z2 and the characteristic curves available with those options use non-integrating
timing. Non-integrating timing is accomplished by timing at a gate that is not solely dependent on the
magnitude of the applied multiple of pickup current. The time-out value is calculated based on the type of
time curve characteristic selected, time dial setting, and the magnitude of the applied multiple of pickup
current. The time-out value is continuously updated during the timing cycle. When pickup is exceeded, a
timer is initiated. When the timer elapsed time exceeds the calculated time-out value, a time trip output
signal is generated.
This type of non-integrating time delay characteristic exhibits a dynamic characteristic that is immediately
responsive to changes of the applied multiple of pickup current.
Integrating Timing
Timing option Z3 and the characteristic curves available for that option uses integrating timing. Integrating
timing is accomplished by summing time increments that are based on the magnitude of the applied
multiple of pickup current, the time curve characteristic selected, and the time dial value. These time
increments are summed until a predetermined value is exceeded, then a time trip output signal is
generated.
This type of integrating time delay characteristic simulates the operating characteristics of an
electromechanical overcurrent relay.
Built-In Test
A built-in test (BIT) switch mounted on the Logic Board provides diagnostic troubleshooting and
calibration.
OPTIONS
Timing
An extended timing option multiplies by approximately 5.7, the standard time delays. The resulting curves
are shown following the standard curves in Appendix A - e.g., Figure A-1 is timing type B1 and Figure A-2
is the timing type B1 with extended timing range.
When timing option Z1, Z2, or Z3 is specified, a printed circuit board mounted selector switch allows a
choice of up to sixteen different time overcurrent functions. Timing option Z1 or Z3 may be further
specified as standard or extended time, depending upon option 2 selection.
Neutral Defeat
When neutral defeat is specified, a front panel switch allows neutral current sensing to be disabled. This
function permits the user to energize desired circuits and not trip because of imbalanced current in the
neutral circuit. After the circuits are balanced, the neutral defeat function can be switched off and neutral
current sensing protection is provided.
Sensing Input Type
When single-phase, two-phase-and-neutral, three-phase, or three-phase-and-neutral sensing has been
specified, the front panel
TAP
selector and the front panel
TAP CAL
control set the pickup point for all
phases. An independent front panel
TAP (NEUTRAL)
selector and front panel
CAL (NEUTRAL)
control
set the neutral pickup point. In addition, for three-phase-and-neutral sensing units, one of the seven
sensing input range combinations must be specified.
Sensing Input Range
For three-phase-and-neutral sensing units, input ranges are:
•
0.5 to 4.0 amperes (phase and neutral)
•
1.5 to 12 amperes (phase) and 0.5 to 4.0 amperes (neutral)
