1-8 BE1-50/51M - General Information
Harmonic Response
BE1-50/51M harmonic rejection is illustrated in Figure 1-4.
Figure 1-4 shows that a relay set for one ampere pickup would pickup at
0.96 ampere on a current containing 40% seventh harmonic. This
corresponds to a ten-to-one rejection ratio. Other conditions may be
evaluated in the same manner.
Figure 1-4. Harmonic Response
INST Characteristics
BE1-50/51M instantaneous characteristic curves are similar to standard
electromechanical instantaneous units. However, the time to trip for
ground applications is slightly longer than that for phase applications to
allow time to power-up the relay. Longer trip time for ground applications
is beneficial because it helps to avoid nuisance trips.
For phase applications, the maximum time to trip is 3.5 cycles at a pickup
multiple of 1.0, and 1.5 cycles at a pickup multiple of 3.0. The
corresponding times for ground applications are 4.5 and 1.75 cycles.
Figure 1-5 shows the instantaneous characteristic curves for maximum
time to trip.
Courtesy of NationalSwitchgear.com