Basler BE1-81, Instruction Manual

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1-1
SECTION 1
GENERAL INFORMATION
PURPOSE
BE1-81 Digital Underfrequency Relays are single-phase, solid-state, protective devices designed to
detect an underfrequency condition and provide an output to actuate external control circuits and/or
alarms. Both 50 hertz and 60 hertz styles are available with either definite time delay or inverse time
delay characteristics.
DESCRIPTION
BE1-81 relays compare the frequency of the applied voltage with a crystal oscillator reference frequency.
When the measured frequency is less than a preset level for a predetermined period of time, external
control circuits and/or alarms are actuated by the relay.
Definite Time Option
Definite time option trip frequency settings are set by three front panel thumbwheel switches. Setting
ranges are between 0.05 and 5.00 hertz in 0.05 hertz increments below nominal system frequency. The
delay time (measured in cycles of the underfrequency waveform) is set by two front panel thumbwheel
switches. Delay ranges are from 01 to 99 cycles. The actual trip time is the delay time setting, plus one
cycle.
Inverse Time Option
Inverse time option trip frequency settings are also set by three front panel thumbwheel switches and the
ranges are from 0.05 to 5.00 hertz in 0.05 hertz increments below nominal system frequency. The
inverse time delay characteristic is inversely proportional to the magnitude of the frequency difference
between the measured waveform and the trip frequency setting. This time may be adjusted to
correspond to a particular characteristic curve by a continuously adjustable front panel time dial. (Refer
to Figures 1-1 and 1-2.)
Relay Assembly
The relay assembly is mounted in a drawout cradle and enclosed in a standard, utility style, semi-flush
case. Individual circuit components are accessible by removal of the individual printed circuit boards
from the relay cradle and using an extender card (Basler part number 9 1655 00 100) to test or
troubleshoot. A front panel, electrically operated, manually reset target may be selected to indicate that a
fault has occurred and the relay has operated. A wide range of options permits the relay to be
specifically tailored to a variety of applications.
MODEL AND STYLE NUMBER DESCRIPTION
BE1-81 Digital Underfrequency Relays electrical characteristics and optional features are defined by a
combination of letters and numbers that make up its style number. The model number, together with the
style number, describe the options included in a specific device, and appear on the front panel, drawout
cradle, and inside the case assembly. Upon receipt of a relay, be sure to check its style number against
the requisition and packing list, to see that they agree.