Basler Electric BE1-851 - Manual (Page 44)

Figure 3-1. Accuracy Characteristics, 55 to 65 Hz
The Average setting uses a digital measurement circuit. This circuit consists of a full wave rectifier with a
two pole, low pass filter. A third digital filter tuned to the nominal frequency removes the ripple error that is
inherent in this type of circuit. Due to the low pass filter, this setting has slower pickup and dropout
characteristics than the other two settings. This setting is recommended in applications where protection
is desired at frequencies that deviate significantly from nominal. The characteristics of the three
algorithms from 20 to 100 Hz is shown in Figure 3-2. This plot is based on a setting of 60 Hz nominal (20
to 100 Hz). This setting also provides good coordination with induction disk type overcurrent relays and
provides superior transient overreach characteristics.
Figure 3-2. Accuracy Characteristics, 20 to 100 Hz
3-2 BE1-851 Input and Output Functions 9289900990 Rev R