Basler BE1-81O/U User manual

Highland, Illinois
Basler Electric
R
SOLID-STATE PROTECTIVE RELAY
UNDER
VOLTAGE
INHIBIT
SETPOINT 1
SETPOINT 2
O
U
U
O
FREQUENCY TIME DELAY PICKUP
SETPOINT
21
POWER
FREQUENCY
BE1-81 O/U
D1278-09
03-23-98
OUT OF
RANGE
+
-
0
+
-
5
+
-
85
-
++
-
10
-
+
+
-
01
-
+
+
-
58
-
+
5
-
+
0
-
+
T3E E1J B7SOF
PICKUP
INSTRUCTION MANUAL
FOR
DIGITAL FREQUENCY RELAY
BE1-81O/U
Publication Number: 9 1373 00 990
Revision: G 06/99

BE1-81O/U - Introduction i
W A R N I N G !
To avoid personal injury or equipment damage, only
qualified personnel should perform the procedures
presented in this manual.
INTRODUCTION
This Instruction Manual provides information concerning the operation and installation of BE1-81O/U
Digital Frequency Relays. Unit Revision E and M to the relay incorporated design changes that are
backward compatible with previous versions of the relay. To accomplish this, the following is
provided.
2
2
Specifications
2
2
Functional Description
2
2
Mounting Information
2
2
Operational Tests

ii BE1-81O/U - Introduction
CONFIDENTIAL INFORMATION
OF BASLER ELECTRIC COMPANY, HIGHLAND, IL. IT IS LOANED FOR
CONFIDENTIAL USE, SUBJECT TO RETURN ON REQUEST, AND WITH THE MUTUAL
UNDERSTANDINGTHATITWILLNOT BE USED IN ANY MANNER DETRIMENTAL TO
THE INTEREST OF BASLER ELECTRIC COMPANY.
First Printing: June 1982
Printed in USA
© 1997, 1998,1999 Basler Electric Co., Highland, IL 62249
June 1999
It is not the intention of this manual to cover all details and variations in equipment, nor does this
manual provide data for every possible contingency regarding installation or operation. The
availability and design of all features and options are subject to modification without notice. Should
further information be required, contact Basler Electric Company, Highland, Illinois.
BASLER ELECTRIC
ROUTE 143, BOX 269
HIGHLAND, IL 62249 USA
http://www.basler.com, [email protected]
PHONE [phone] FAX [phone]

BE1-81O/U - Introduction iii
CONTENTS
Section 1 GENERAL INFORMATION 1-1
Description..................................................1-1
Applications.................................................1-1
Model and Style Number.......................................1-2
Style Number Example.....................................1-2
Style Number Identification Chart..............................1-2
Specifications................................................1-3
Section 2 HUMAN MACHINE INTERFACE (Controls And Indicators) 2-1
Section 3 FUNCTIONAL DESCRIPTION 3-1
General....................................................3-1
Functional Description.........................................3-1
Sensing Input.............................................3-1
Undervoltage Inhibit........................................3-1
Zero-Crossing Logic........................................3-4
Crystal Oscillator..........................................3-4
Period Clock Generator.....................................3-4
Minimum Period Difference Logic..............................3-4
Maximum Period Difference Logic.............................3-5
Measured Frequency Converter...............................3-5
Frequency Comparator Logic.................................3-5
Definite Time Delay Logic...................................3-5
Inverse Time Delay Logic....................................3-5
Relay Output.............................................3-6
Auxiliary Relay Output......................................3-6
Target..................................................3-6
Power Supply............................................3-6
Power Supply Status Output.................................3-6
Section 4 INSTALLATION 4-1
General....................................................4-1
Relay Operating Precautions....................................4-1
Dielectric Test...............................................4-1
Mounting...................................................4-1
Connections.................................................4-1
Section 5 TESTS AND ADJUSTMENTS 5-1
General....................................................5-1
Required Test Equipment.......................................5-1
Operational Test.............................................5-1
High and Low Frequency Pickup..............................5-1
Frequency Selector Settings.................................5-2
Definite TIME DELAY (Option E1).............................5-3
Definite TIME DELAY (Option E2).............................5-3

iv BE1-81O/U - Introduction
CONTENTS - Continued
Operational Test Procedure - Continued
Inverse TIME DELAY (Option D1) ............................ 5-4
Undervoltage Inhibit ....................................... 5-5
SETPOINT 2, 3, and 4 Performance Tests ...................... 5-5
Section 6 MAINTENANCE 6-1
General ................................................... 6-1
In-House Repair ............................................. 6-1
Storage ................................................... 6-1
Test Plug .................................................. 6-1
Section 7 MANUAL CHANGE INFORMATION 7-1
LIST OF ILLUSTRATIONS
Figure 1-1. Style Number Identification Chart ............................. 1-2
Figure 1-2. Inverse Time Overfrequency Characteristic Curves ............... 1-6
Figure 1-3. Inverse Time Underfrequency Characteristic Curves .............. 1-7
Figure 2-1. Location of Controls and Indicators ............................ 2-2
Figure 2-2. Location of Controls and Indicators, S1 Case .................... 2-3
Figure 2-3. Definite Time Board Switch S7 ............................... 2-4
Figure 3-1. Bandpass Filter Characteristics .............................. 3-1
Figure 3-2. BE1-81O/U Functional Block Diagram ......................... 3-2
Figure 3-3. Location of Assemblies (Typical M1 Case) ...................... 3-3
Figure 3-4. Location of Assemblies (Typical S1 Case) ...................... 3-4
Figure 4-1. S1 Case, Panel Drilling Diagram, Semi-Flush Mounting ............ 4-2
Figure 4-2. S1 Case, Outline Dimensions, Front View ...................... 4-3
Figure 4-3. S1 Case, Double-Ended, Semi-flush Mounting, Side View .......... 4-4
Figure 4-4. S1 Case, Single-Ended, Semi-flush Mounting, Side View ........... 4-5
Figure 4-5. S1 Case, Single-Ended, Semi-flush Mounting, Outline Dimensions . . . 4-6
Figure 4-6. S1 Case, Double-Ended, Projection Mounting, Panel Drilling Diagram . 4-7
Figure 4-7. S1 Case, Double-Ended, Projection Mounting, Rear View .......... 4-8
Figure 4-8. S1 Case, Double-Ended, Projection Mounting, Side View ........... 4-9
Figure 4-9. M1 Case, Semi-flush Mounting, Panel Drilling Diagram ............ 4-10
Figure 4-10. M1 Case, Outline Dimensions, Front View ...................... 4-11
Figure 4-11. M1 Case, Double-Ended, Semi-flush Mounting, Side View .......... 4-12
Figure 4-12. M1 Case, Single-Ended, Semi-flush Mounting, Side View ........... 4-13
Figure 4-13. M1 Case, Single-Ended, Projection Mounting, Panel Drilling Diagram . . 4-14
Figure 4-14. M1 Case, Single-Ended, Projection Mounting, Outline Dimensions .... 4-15
Figure 4-15. M1 Case, Double-Ended, Projection Mounting, Panel Drilling Diagram . 4-16
Figure 4-16. M1 Case, Double-Ended, Projection Mounting, Outline Dimensions . . . 4-17
Figure 4-17. M1 Case, Double-Ended, Projection Mounting, Side View .......... 4-18
Figure 4-18. Internal Connections ...................................... 4-19
Figure 4-19. DC Connections .......................................... 4-20
Figure 4-20. AC Sensing Connections ................................... 4-20
Figure 5-1. Test Setup Diagram ....................................... 5-2

BE1-81O/U - General Information 1-1
SECTION 1 • GENERAL INFORMATION
DESCRIPTION
Digital Frequency Relay, BE1-81 O/U, is a solid-state protective device that monitors the frequency of a
single-phase ac voltage to provide accurate frequency protection for distribution systems and generators.
The protected system operating frequency can be 50 hertz or 60 hertz.
The relay is designed to permit removal of a load from a distribution system when the system frequency falls
below a setpoint. The relay will permit restoration of the load when the system frequency returns to normal
as defined by another setpoint. Also, the relay may be tailored to the operating frequency/time characteristic
of a generator to permit the removal of the generator from service if the generator output frequency (or
system frequency) exceeds a setpoint. This scheme also permits restoration to service when the generator
(or system) frequency returns to normal.
APPLICATIONS
BE1-81 O/U Digital Frequency Relays sense frequency between the limits of 30 and 80 hertz. The relays
provide up to four independently adjustable frequency/time delay setpoints with corresponding output relays.
Each setpoint may be set to recognize either overfrequency or underfrequency. When the sensed frequency
passes through a setpoint in the selected direction, timing begins. If the condition continues for three cycles,
the PICKUP LED lights. After the selected time delay times out, the associated setpoint output relay
energizes. When the frequency returns through the setpoint and remains there for three cycles, the output
relay resets.
Each FREQUENCY selector provides setpoint selection over the range of 40 to 70 hertz. TIME DELAY is
available with either definite time or inverse time characteristics. Refer to Figure 1-1 for style selections.
Inverse time delay (option D1) is inversely proportional to the magnitude of the difference between the
detected frequency and the setpoint frequency. This relationship may be tailored to the application by means
of the characteristic response curves.
Definite time delay (option E1) setpoints are selectable over the range of three to 99 cycles.
Definite time delay (option E2) setpoints are field selectable for time delays in seconds or cycles. Each
setpoint is selectable over the range of three to 990 cycles or 0.1 to 99 seconds.
The FREQUENCY and TIME DELAY selectors for the setpoints are accessible at the front panel. Each
FREQUENCY setpoint includes an O/U switch for selecting whether the setpoint will respond to either an
overfrequency (O) or underfrequency (U).
An undervoltage inhibit circuit prevents relay operation if the sensed voltage falls below the setting (factory
set at 80 Vac, but is front panel-adjustable over the range of 40-120 Vac). If inverse time delay is installed
and either maximum frequency measurement limit is exceeded, the magnitude of the delay will remain at the
value determined at the frequency limit. Targets, either internally operated or operated by current in the
output circuit, are available for all of the setpoints in the relay.
When one or two setpoints are specified, the relay is supplied in an S1 style case. When three or four
setpoints are specified, the relay is supplied in an M1 style case.
The relay assembly is mounted in a drawout cradle. Test points and circuit components are accessible by
removing the individual printed circuit boards from the cradle and using an extender board (Basler part
number 9 1655 00 100) to test or troubleshoot. An available test plug (Basler part number 10095 or G.E. part
number 12XLA12A1) enables the relay to be tested in place without distributing external control circuit wiring.

D2856-20
6/30/99
1-2 BE1-81O/U - General Information
MODEL AND STYLE NUMBER
The electrical characteristic and operational features included in a specific relay are defined by a combination
of letters and numbers that make up the relay style number. The style number together with the model
number describethefeatures and options in a particular unit and appear on the front panel, drawout cradle,
and inside the case assembly. The model number BE1-81 O/U designates the relay as a Basler electric,
Class 100, Digital Frequency Relay.
Style Number Example
The style number identification chart shown in Figure 1-1 illustrates the features and options for BE1-81 O/U
relays. For example, if the style number were BE1-81 O/U T3E E1J A9N2F, the unit would have the following
features.
BE1-81 O/U Model number
TSingle-phase sensing type
3100/120 Vac, 40-70 hertz nominal sensing range
EOne normally open output relay per setpoint
E1 Definite time delay
JOperating power derived from 125 Vdc or 120 Vac source
AOne internally operated target for each setpoint
9Four setpoints
NNo power supply status output
2One normally closed auxiliary relay output for each setpoint
FSemi-flush mounting
Figure 1-1. Style Number Identification Chart

BE1-81O/U - General Information 1-3
SPECIFICATIONS
BE1-81 O/U Digital Frequency Relays have the following features and capabilities.
Sensing Input The frequency sensing input is rated for 132 Vac maximum continuous
at 50/60 hertz at a maximum burden of 2 VA. Input voltage can vary
between 40 and 132 Vac. The input frequency is detectable between
the limits of 30 and 80 hertz (relays unit revision D and subsequent). For
relays revision C and previous, the input frequency is detectable
between the limits of 35 and 80 hertz. Accurate computation occurs
between the nominal limits of 40 and 70 hertz.
Output Circuits One relay output is provided for each setpoint. Relay outputs are
normally open or normally closed as specified. One normally open or
normally closed auxiliary relay output per setpoint is also provided, if
ordered.
Output Contacts Output contacts are rated as follows:
Resistive
120/240 Vac - Make 30 A for 0.2 seconds, carry 7 A continuously, and
break 7 A.
125/250 Vdc - Make and carry 30 A for 0.2 seconds, carry 7 A
continuously, break 0.3 A.
Inductive
120/240 Vac, - Make and carry 30 A for 0.2 seconds, carry 7 A
125/250 Vdc continuously, break 0.3 A. (L/R = 0.04).
Power Input Internal relay operating power may be obtained from a wide variety of
external voltage sources. When ordering, any one of five internal power
supplies may be selected to match operating power input voltage level to
available external voltage sources. Available power supplies are shown
in Table 1-1.
Table 1-1. Power Supply Options
Type Voltage Range Nominal
Nominal Input Input Voltage Burden at
K (Mid Range) 48 Vdc 24 to 150 Vdc 4.4 W
J (Mid Range) 125 Vdc 24 to 150 Vdc 4.4 W
120 Vac 90 to 132 Vac 10.1 VA
†L (Low Range) 24 Vdc 12 to 32 Vdc 4.5 W
Y (Mid Range) 48 Vdc 24 to 150 Vdc 4.4 W
125 Vdc 24 to 150 Vdc 4.4 W
Z (High Range) 250 Vdc 68 to 280 Vdc 5.5 W
230 Vac 90 to 270 Vac 14.0 VA
† Type L power supply may require 14 Vdc to begin operating. Once
operating, the voltage may be reduced to 12 Vdc.
Target Indicators Target indicators may be either internally operated or current operated
(operated by a minimum of 0.2 A through the output trip circuit). When
the target is current operated, the trip output circuit current must be
limited to 30 A for 1 second, 7 A for 2 minutes, and 3 A continuously.


1-4 BE1-81O/U - General Information
Setpoint Frequency Thumbwheel switches provide frequency pickup settings in increments
Selectors of 0.01 hertz.
Pickup ±0.01 hertz of the set value.
Time Delay Adjustability
Definite Time Option E1 & E2 Field selectable range is 3 to 99 cycles in 1 cycle increments, 10 to 990
cycles in 10 cycle increments, 0.1 to 9.9 seconds in 0.1 second
increments, or 1 to 99 seconds in 1 second increments. Settings 00, 01,
or 02 cycles operate the same as 03 cycles because the timing circuits
require 3 cycle continuous excursion through the setpoint before tripping
the output circuit.
Inverse Time Option TIME DELAY setting is 0.1 to 9.9 (99 curve settings). The characteristic
curve plot points shown in Figures 1-2 and 1-3 are calculated from the
following equation. (All possible curves are NOT shown on the graphs.)
Curve plot point range (time delay in seconds) is 0.1 to 100 seconds for
a frequency difference of 0 to 10 hertz from the FREQUENCY setpoint.
Actual time delay is the sum of the elapsed time for three cycles of the
input frequency (timing circuits require three cycle continuous excursion
through the setpoint) plus the time for the plotted point on the curve.
Time Delay Accuracy
Definite Time Options E1, E2 ±1.0 cycle for delay settings in cycles. For delay settings in seconds,
±2% of the setting or 25 milliseconds whichever is greater.
Inverse Time Option D1 Within 5% of the selected characteristic curve plus 3 cycles of the
sensed frequency for a given step change in frequency, over a sensing
range of 40 to 132 Vac at 25 ( C.
Undervoltage Inhibit Within ±5% of the setting at 25 ( C for nominal frequency input.
Accuracy
UL Recognized UL Recognized per Standard 508, UL File No. E97033. Note: Relay is
not UL Recognized for output contact voltages greater than 250 volts
and input power supply voltages greater than 150 volts.
Isolation Meets IEC 255-5 and exceeds ANSI/IEEE C37.90 one-minute dielectric
tests as follows:
All circuits to ground: 2828 Vdc.
Input to output circuits: 2000 Vac or 2828 Vdc
Radio Frequency Field Tested using a five watt, hand-held transceiver operating at
Interference (RFI) random frequencies centered around 144 MHz and 440 MHz, with the
antenna located six inches from the relay in both horizontal and vertical
planes.
Maintains proper operation when tested for interference in accordance
with IEC C37.90-1989, Trial-Use Standard Withstand Capabilit
y
of Rela
y
S
y
stems to Radiated Electroma
g
netic Interference from Transceivers.
Surge Withstand Capability Qualified to ANSI/IEEE C37.90.1-1989
Standard Surge Withstand

BE1-81O/U - General Information 1-5
Capability (SWC) Tests for Protective Relays and Relay Systems.
Fast Transient Qualified to ANSI/IEEE C37.90.1-1989.
Impulse Test Qualified to IEC 255-5.
Shock 15 g in each of three mutually perpendicular axes.
Vibration 2 g in each of three mutually perpendicular axes swept over the range of
10 to 500 hertz for a total of 6 sweeps, 15 minutes each sweep.
Temperature
Operating Range -40 ( C (-40 ( F) to 70 ( C (158 ( F)
Storage Range -40 ( C (-40 ( F) to 85 ( C (185 ( F)
Weight Approximately 18 pounds (M1 case) or 13 pounds (S1 case) net.
Case Size M1 (three or four setpoints) or S1 (one or two setpoints).

1-6 BE1-81O/U - General Information
Figure 1-2. Inverse Time Overfrequency Characteristic Curves

BE1-81O/U - General Information 1-7
Figure 1-3. Inverse Time Underfrequency Characteristic Curves

BE1-81O/U - Human Machine Interface (Controls And Indicators) 2-1
SECTION 2 • HUMAN MACHINE INTERFACE
(Controls And Indicators)
DESCRIPTION
Table 2-1 lists and briefly describes the operator controls and indicators of the BE1-81O/U Digital Frequency
Relay. Reference the call-out letters to Figures 2-1, 2-2, and 2-3.
Table 2-1. BE1-81 O/U Controls and Indicators
Locator Control or Indicator Function
A TIME DELAY Selector A set of two thumb-wheel switches selects the time delay
between setpoint pickup and output relay reaction. There
is one set of switches per setpoint.
B PICKUP LED Red LED is ON when sensed frequency exceeds the
setpoint. The LED remains ON until the sensed
frequency is less than the setpoint. One LED per
setpoint.
C Power LED LED is ON when the relay power supply is supplying a
nominal ±12 Vdc to the internal circuitry.
D Target Reset Lever Linkage extends through bottom of front cover to reset all
magnetically latched target indicators.
E SETPOINT Targets Black target indicator trips to red and is magnetically
latched when the associated output relay is energized.
One for each SETPOINT.
F O/U Selector Two-position toggle switch allows selection of an
overfrequency (O) or underfrequency (U) function of the
corresponding frequency selector. One for each
SETPOINT.
G FREQUENCY Selector A set of four thumbwheel switches, selects the setpoint
frequency in increments of 0.01 Hz over an allowable
range of 40 to 70 Hz. One for each SETPOINT.
H UNDER VOLTAGE INHIBIT Red LED is ON when the sensed input drops below the
LED UNDER VOLTAGE INHIBIT adjustment level.
I UNDER VOLTAGE INHIBIT Adjusts the undervoltage inhibit level between 40 and 120
Adjustment Vac. Relay operation is inhibited if the sensed voltage
falls below the setting. The nominal factory setting is 80
Vac. Adjustment is by a small screwdriver through the
front panel.

+
-
57
-
+
5
-
+
0
-
+
+
-
4
+
-
+
-
85
-
+
+
-
0
+
-
5
+
-
85
-
+
+
-
0
+
-
5
+
-
85
-
+
+
-
10
-
+
+
-
05
-
+
+
-
10
-
+
+
-
10
-
+
SETPOINT 4
SETPOINT 3
SETPOINT 2
SETPOINT 1
FREQUENCY TIME DELAY
UNDER
VOLTAGE
INHIBIT
U
O
U
O
POWER
12
FREQUENCY
BE1-81 O/U
Hi
g
hland, Illinois
Basler Electric
R
SOLID-STATE PROTECTIVE RELAY
PICKUP
4
SETPOINT
PICKUP
PICKUP
PICKUP
T3E E1J B7SOF
03-17-98
D1185-07
D
E
F
C
B
A
H
I
G
0
3
O
U
O
U
2-2 BE1-81O/U - Human Machine Interface (Controls And Indicators)
Figure 2-1. Location of Controls and Indicators

BE1-81O/U - Human Machine Interface (Controls And Indicators) 2-3
Table 2-1. BE1-81 O/U Controls and Indicators - Continued
Locator Control or Indicator Function
J OUT OF RANGE LED LED is ON when the sensed frequency is outside the
sensing range of 35 to 80 Hz.
K Selector Switch S7 Field selectable, three section switch for selecting definite
(Definite Time Option E1 time delay in seconds or cycles and a multiplier of X1,
and E2) X10 or X100.
S7-1and S7-2 select the multiplier. Down selects X1 and
up selects X10. Section 1 and section 2 are marked on
the switch, and the multiplier positions are marked on the
circuit board. Either switch can be used to select X10
multiplier. For X100, both switches must be set for X10.
S7-3 selects seconds (S) or cycles (C). Down selects
seconds and up selects cycles. Section 3 is also marked
on the switch; S and C are marked on the circuit board.
Figure 2-2. Location of Controls and Indicators S1 Case (Relays Revision C and Previous)

K
D2856-19
6-26-92
2-4 BE1-81O/U - Human Machine Interface (Controls And Indicators)
Figure 2-3. Definite Time Board Switch S7 (Definite Time Option E1 or E2)

FREQUENCY(HZ)
dB
12
13
14
15
16
17
18
12 40 60 80 100 120 140 160 180 200
BE1-81O/U - Functional Description 3-1
SECTION 3 • FUNCTIONAL DESCRIPTION
GENERAL
Digital Frequency Relays, BE1-81 O/U provide one to four frequency setpoints for monitoring under and
overfrequency conditions of an ac source within the nominal limits of 40 hertz to 70 hertz. When the relay
senses that a setpoint is exceeded, an output relay is energized after a selectable time delay. The
undervoltage inhibit circuit prevents relay operation if the sensed ac source voltage decreases below this
limit.
FUNCTIONAL DESCRIPTION
The following paragraphs describe the functional operation of the relay.
Sensing Input
Because input signal zero crossings are used to measure the input frequency, it is necessary to filter
unwanted harmonics and transients. Some attenuation of the input signal results. Figure 3-1 illustrates this
attenuation in dB for input frequencies.
Figure 3-1. Bandpass Filter Characteristics
A single-phase voltage is applied to an input signal conditioning circuit (transformer and bandpass filter,
Figure 3-2). The sensed input signal is applied to the zero crossing logic and undervoltage detect circuits.
Refer to Figures 3-3 and 3-4 for the location of assemblies.
Undervoltage Inhibit
This circuit prevents the output relay(s) from energizing during an undervoltage condition associated with
equipment startup. The circuit prevents operation of the zero cross logic and the time delay logic, and lights
the UNDER VOLTAGE INHIBIT LED when the level of the sensed voltage is less than the setting. The inhibit
level is factory set to 80 Vac (nominal), but may be adjusted between 40 and 120 Vac.

INTERNAL
+/-12 VOLT
POWER
CROSS
ZERO
CIRCUIT
CIRCUIT
CIRCUIT
TO TRIP
TO TRIP
TO TRIP
D1185-06
03-18-98
RELAY
OUTPUT
SUPPLY
POWER
STATUS
SUPPLY
POWER
LEVER
RESET
MANUAL
CLOCK
PERIOD
SENSOR
SUPPLY
POWER
POWER
POWER INPUT
LIMITS
BEYOND
FREQUENCY
BCD BUS
DATA
SELECT
FREQUENCY
SELECT
O/U
LOGIC
COMPRERATOR
FREQUENCY
UNDER VOLTAGE
DELAY
TIME
LOGIC
DELAY
TIME
PICKUP
EOPR
OVER FREQUENCY UNDER
IONING
CONDIT-
SIGNAL
INPUT
LED
VOLTAGE
UNDER
DETECT
VOLTAGE
UNDER
BCD FREQUENCY DATA
UNDER VOLTS
SIGNAL
CONDITIONED
2 MHZ
1 MHZ
AC INPUT SIGNAL
SETPOINT 3
SETPOINT 4
SETPOINT 2
SETPOINT 1
OPTIONS 1-7, 1-8, 1-9
F1 OVER/UNDER
TARGET
MAXIMUM
DIFFERENCE
LOGIC
DIFFERENCE
PERIOD
MINIMUM
LOGIC
PERIOD
CONVERTER
FREQUENCY
MEASURED
RANGE
OUT OF
LOGIC
CROSSING
ZERO
CLOCK
OSILLATOR
CRYSTAL
FREQUENCY
SELECT
DRIVER
TARGET
AUX.
OUTPUT
TO TRIP
CIRCUIT
OPTIONS 1-8, 1-9
OPTIONS 1-8
OPTION 2-S
PERIOD
GEN.
3-2 BE1-81O/U - Functional Description
Figure 3-2. BE1-81O/U Functional Block Diagram

FREQUENCY MEASUREMENT
BOARD ASSEMBLY
POWER SUPPLY
MOTHER BOARD
ASSEMBLY
MAGNETICS
INDICATOR BOARD
ASSEMBLY
D1185-08
6-29-92
ASSEMBLY
BOARD ASSEMBLY
TYPICAL SETPOINT
LOWER
BE1-81O/U - Functional Description 3-3
Figure 3-3. Location of Assemblies (Typical M1 Case)

3-4 BE1-81O/U - Functional Description
Figure 3-4. Location of Assemblies (Typical S1 Case)
Zero Crossing Logic
The zero crossinglogic circuit converts the sensed frequency to pulses synchronized to each positive-going
zerocrossing of the waveform. The pulse frequency represents the period of the waveform and is applied
to the period clock generator, minimum period difference logic, and maximum period difference logic circuits.
Crystal Oscillator
The crystal-controlled oscillator provides accurate 1 MHZ and 2 MHZ timing signals for the clock logic.
Period Clock Generator
A frequency comparison is made for each cycle of sensed frequency. The period clock generator generates
a reference signal that is synchronized with the beginning of each cycle of the sensed frequency. At each
zero crossing pulse, the clock gates the two megahertz period clock pulses to the minimum period difference
logic circuit.
Minimum Period Difference Logic
Each zero cross pulse causes this logic to count 24580 two-megahertz clock pulses which is the period of
the 80 hertz maximum detectable frequency limit. When the sensed frequency is less than the limit, an
EOPR (end of period reference) pulse is generated to initiate the maximum period difference and
measurement logic.
However, if the sensed frequency equals or exceeds the 80 hertz maximum frequency limit (zero cross
pulses interrupt the counts) for three consecutive cycles, the maximum period difference logic is bypassed.
On relays revision C and previous, the OUT OF RANGE LED lights. The measured frequency converter then
computes the frequency at this maximum frequency limit. If inverse time delay is present in the relay, the
time delay is determined as though the frequency were at the maximum frequency limit. The definite time
delay, if present, is not affected by the frequency limit being exceeded.