Basler Electric BE1-81O/U - Manual (Page 7)

9137300990 Rev N 1
Introduction
The BE1-81O/U Digital Frequency Relay monitors the frequency of a single-phase, ac voltage and
provides accurate frequency protection for a distribution system or generator operating at 50 or 60 hertz.
The BE1-81O/U initiates removal of a load from a distribution system when the system frequency
decreases below the relay’s adjustable setpoint. When the system frequency returns to normal (as
defined by another setpoint), the BE1-81O/U permits restoration of the load. The BE1-81O/U may be
tailored to the operating frequency/time characteristic of a generator to permit removal of the generator
from service if the generator frequency (or system frequency) exceeds a setpoint. This scheme also
permits restoration to service when the generator (or system) frequency returns to normal.
Features
The BE1-81O/U can be specified with up to four independently adjustable frequency setpoints and time
delays with associated output relays and target indicators.
Frequency Setpoints
Each frequency setpoint has a setting range of 40 to 70 hertz and can be switch-selected to detect over-
frequency or underfrequency. BE1-81O/U relays with one or two setpoints are supplied in an S1 case.
Relays with three or four setpoints are supplied in an M1 case.
Time Delays
Each definite time delay setting can be adjusted for a delay of three cycles to 990 seconds.
Undervoltage Inhibit
An undervoltage inhibit feature prevents relay operation if the sensed voltage decreases below the
adjustable front-panel setting.
Targets
Either internally-operated or current-operated target indicators are available for each setpoint.
Operation
When the sensed frequency passes through a setpoint in the selected direction, a three-cycle timer
begins timing. If the condition persists for the duration of the three-cycle timer, the Pickup LED indicator
lights and the definite time delay is triggered. If the pickup condition persists for the duration of the Time
Delay setting, the corresponding output relay energizes, operates the appropriate output contacts, and
trips the setpoint’s target indicator.
Style Number
BE1-81O/U electrical characteristics and operating features are defined by a combination of letters and
numbers that make up the relay style number. The style number describes the features and options of a
particular relay and appears on the front panel, draw-out cradle assembly, and the relay case. The style
number identification chart shown in Figure 1 illustrates the features and options for the BE1-81O/U relay.
BE1-81O/U Introduction