Basler BE1-59N User manual

INSTRUCTION MANUAL
FOR
GROUND FAULT OVERVOLTAGE RELAY
BE1-59N
P0050-20
Publication: 9171400990
Revision: G 09/07

9171400990 Rev G BE1-59N Introduction i
INTRODUCTION
This instruction manual provides information about the operation and installation of the BE1-59N Ground
Fault Overvoltage Relay. To accomplish this, the following information is provided:
•General Information and Specifications
•Controls and Indicators
•Functional Description
•Installation
•Testing
WARNING!
To avoid personal injury or equipment damage, only qualified personnel should
perform the procedures in this manual.
NOTE
Be sure that the relay is hard-wired to earth ground with no smaller than 12 AWG
copper wire attached to the ground terminal on the rear of the unit case. When
the relay is configured in a system with other devices, it is recommended to use a
separate lead to the ground bus from each unit.

ii BE1-59N Introduction 9171400990 Rev G
First Printing: November 1986
Printed in USA
© 1986, 2001-2002, 2007 Basler Electric, Highland Illinois 62249 USA
All Rights Reserved
September 2007
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.
BASLER ELECTRIC
ROUTE 143, BOX 269
HIGHLAND IL 62249 USA
http://www.basler.com, [email protected]
PHONE [phone] FAX [phone]
CONFIDENTIAL INFORMATION
of Basler Electric, Highland Illinois, USA. It is loaned for confidential use, subject
to return on request, and with the mutual understanding that it will not be used in
any manner detrimental to the interest of Basler Electric.

9171400990 Rev G BE1-59N Introduction iii
REVISION HISTORY
The following information provides a historical summary of the changes made to the BE1-59N instruction
manual (9171400990). Revisions are listed in reverse chronological order.
Manual
Revision and Date Change
G, 09/07 •Updated Output Contact ratings in Section 1.
•Moved content of Section 6, Manual Change Information to Manual
Introduction.
•Updated front panel illustrations to show laser graphics.
•Moved Testing content of Section 4, Installation to Section 5, Testing.
•Added manual part number and revision to all footers.
•Updated power supply burden data in Section 1.
•Updated Target Indicator description in Section 3.
•Added GOST-R to Section 1, General Information.
F, 04/02 •Revised the power supply information in Sections 1 and 3.
E, 12/01 •Updated power supply information in the style chart on page 1-3 and
in the example on page 1-2.
•Updated pickup voltage ranges and accuracies on page 1-4.
•Updated power supply description paragraphs on page 3-3.
•Updated unit case covers on pages 4-9 and 4-10.
•Updated drawings of front cover to show the new pushbutton
switches instead of the thumbwheel switches.
D, 01/93 •New style chart (new option 1-2 and expanded option 1-1).
•Restructured the entire manual to conform to manual updates.
C •Accuracy specification for the Definite Timing Characteristic was
clarified and upgraded on page 1-4.
•Output contact specifications were updated.
B •Incorporated new timing option F7 in the manual.
•K was clarified for the various options on page 2-3.
A •Accuracy specification for the Inverse Timing Characteristic was
clarified and upgraded on page 1-4.
—, 11/86 •Initial release

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9171400990 Rev G BE1-59N Introduction v
CONTENTS
SECTION 1 •GENERAL INFORMATION................................................................................................ 1-1
PURPOSE........................................................................................................................................... 1-1
APPLICATION .................................................................................................................................... 1-1
High Resistance Grounding.......................................................................................................... 1-1
Ungrounded Systems................................................................................................................... 1-2
MODEL AND STYLE NUMBER.......................................................................................................... 1-2
Style Number Example................................................................................................................. 1-3
SPECIFICATIONS.............................................................................................................................. 1-4
Voltage Sensing Inputs................................................................................................................. 1-4
Undervoltage Sensing Input Range ............................................................................................. 1-4
Pickup Accuracy........................................................................................................................... 1-4
Dropout......................................................................................................................................... 1-4
Timing Characteristics.................................................................................................................. 1-4
Output Contacts............................................................................................................................ 1-4
Power Supply................................................................................................................................ 1-5
Target Indicators........................................................................................................................... 1-5
Type Tests.................................................................................................................................... 1-5
Physical ........................................................................................................................................ 1-6
Agency Recognition/Certification ................................................................................................. 1-6
SECTION 2 •CONTROLS AND INDICATORS ....................................................................................... 2-1
INTRODUCTION................................................................................................................................. 2-1
SECTION 3 •FUNCTIONAL DESCRIPTION........................................................................................... 3-1
INTRODUCTION................................................................................................................................. 3-1
INPUTS............................................................................................................................................... 3-1
FILTERS ............................................................................................................................................. 3-1
OVERVOLTAGE COMPARATOR...................................................................................................... 3-1
DEFINITE TIME DELAY (OPTIONAL)................................................................................................ 3-1
INVERSE TIME DELAY (OPTIONAL)................................................................................................ 3-2
REFERENCE VOLTAGE CIRCUIT.................................................................................................... 3-2
UNDERVOLTAGE ELEMENT (OPTIONAL)....................................................................................... 3-2
Undervoltage Operation ............................................................................................................... 3-2
Undervoltage Inhibit...................................................................................................................... 3-2
OUTPUTS........................................................................................................................................... 3-2
PUSH-TO-ENERGIZE
OUTPUT PUSHBUTTONS............................................................................ 3-2
POWER SUPPLY STATUS OUTPUT................................................................................................ 3-3
POWER SUPPLY ............................................................................................................................... 3-3
TARGET INDICATORS ...................................................................................................................... 3-3
Internally Operated Targets.......................................................................................................... 3-3
Current Operated Targets ............................................................................................................ 3-3
SECTION 4 •INSTALLATION.................................................................................................................. 4-1
INTRODUCTION................................................................................................................................. 4-1
RELAY OPERATING GUIDELINES AND PRECAUTIONS ............................................................... 4-1
MOUNTING......................................................................................................................................... 4-1
CONNECTIONS.................................................................................................................................. 4-9
MAINTENANCE................................................................................................................................ 4-12
STORAGE......................................................................................................................................... 4-12
SECTION 5 •TESTING ............................................................................................................................ 5-1
INTRODUCTION................................................................................................................................. 5-1
OPERATIONAL TEST ........................................................................................................................ 5-1

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9171400990 Rev G BE1-59N General Information 1-1
SECTION 1 •GENERAL INFORMATION
PURPOSE
The available fault current for single-phase-to-ground faults is very limited for ungrounded systems and
systems, which are grounded through a high resistance. This current limiting reduces the possibility of
extensive equipment damage, and eliminates the need for a neutral breaker by reducing the fault current
below the level required to sustain an arc. However, it remains important to detect and isolate single-
phase-to-ground faults in order to prevent their evolution into more dangerous faults such as phase-to-
phase-to-ground and three-phase-to-ground faults. Sensitive voltage relays can be used to detect ground
faults where the fault current is very small. The BE1-59N Ground Fault Overvoltage Relay is especially
suited to this task.
APPLICATION
High Resistance Grounding
A common method of grounding an ac generator is to connect a distribution transformer between the
neutral of the generator and the station ground. The distribution transformer's primary voltage rating is
equal to, or greater than, the generators rated line-to-neutral voltage. The distribution transformer
secondary is rated at 200/240 Vac or 100/120 Vac, and a resistor is connected across the secondary
winding. When reflected through the transformer, the resistor is effectively a high resistance.
Rp= Rsx N2
Where:Rpis the effective primary resistance
Rsis the actual value of the secondary resistor
N is the turns ratio of the distribution transformer
To determine resistor sizing:
•Determine the thermal limit P (in watts) of the voltage transformers.
•Use R
Vpri
V=
2
sec)( to determine resistance in ohms, where Vsec = 120 x 3 = 360V. This assumes a
120V VT secondary in a worst-case condition.
•Size the watt rating of the resistor for 1/3 of the VT thermal limit to keep the resistor from excessive
heating. A smaller watt rating can be used if tripping for a ground condition.
Available single-phase-to-ground fault current at the generator terminals is greatly reduced by the high
effective resistance of the distribution transformer and secondary resistor. The distribution transformer
provides isolation for the protection scheme and reduces the voltage to a convenient level.
The BE1-59N Ground Fault Overvoltage Relay is connected across the secondary resistor to detect the
increase in voltage across the distribution transformer caused by a ground fault in the generator stator
windings. A ground fault at the generator terminals will result in rated line-to-neutral voltage across the
transformer primary, while ground faults near the neutral will result in lower voltages. The overvoltage
relay setpoint must be higher than any neutral voltage caused by normal unbalances in order to avoid
nuisance trips. This will allow a certain percentage of the stator windings to go unprotected by the
overvoltage relay. The overvoltage relay function typically protects 90 to 95% of the generator stator
windings.
The BE1-59N Ground Fault Overvoltage Relay monitors the fundamental frequency (50 or 60 Hz)
voltage, which accompanies a ground fault, but is insensitive to the third harmonic voltage present during
normal operation. One hundred percent protection of the generator stator windings is obtainable with the
optional overlapping undervoltage element. The under voltage element is tuned to the third harmonic
voltage which is present in the generator neutral under normal conditions. The undervoltage element
detects the reduction of the normal third harmonic voltage, which accompanies a ground fault near the
neutral point of the generator.
An undervoltage inhibit feature is included with the third harmonic undervoltage element. This feature
supervises the operation of the ground fault relay to prevent operation during startup and shutdown by
monitoring the generator terminal voltage.

1-2 BE1-59N General Information 9171400990 Rev G
Ungrounded Systems
The BE1-59N Ground Fault Overvoltage Relay is used to detect ground faults on ungrounded three-
phase-three-wire systems. The relay is connected as shown in Figure 1-1. A set of voltage transformers
are wired with a grounded wye primary and a broken delta secondary. The BEl-59N is connected across
the broken delta. It is often necessary to connect a resistor across the broken delta to avoid
ferroresonance.
Grounded wye/broken delta voltage transformers act as a zero sequence filters by summing the three
phase voltages. Under normal conditions, this sum is zero. When a ground fault occurs, the BE1-59N
Ground Fault Overvoltage Relay will detect the presence of the secondary zero sequence voltage (3VO).
The BE1-59N Ground Fault Overvoltage Relay greatly reduces the risk of equipment damage by
detecting and isolating the first ground on an ungrounded system.
Figure 1-1. Ungrounded 3-Phase, 3-Wire System
MODEL AND STYLE NUMBER
BE1-59N electrical characteristics and operational features are defined by a combination of letters and
numbers that make up the style number. Model number BE1-59N designates the relay as a Basler
Electric Ground Fault Overvoltage Protective Relay. The model number, together with the style number,
describes the options included in a specific device and appears on the front panel, draw-out cradle, and
inside the case assembly.
The style number identification chart for the BE1-59N relay is illustrated in Figure 1-2.

9171400990 Rev G BE1-59N General Information 1-3
Figure 1-2. BE1-59N Style Identification Chart
Style Number Example
If a BE1-59N relay has a style number of A5F–F6J–D2S3F, the relay has the following features:
A--------Single-phase voltage sensing input
5--------120 Vac, 60 Hz nominal sensing voltage input with 1 to 20 Vac pickup range
F--------Two output relays with normally open (NO) contacts (one overvoltage and one undervoltage)
F6 ------Inverse time delay for overvoltage and definite time delay for undervoltage
J--------Relay control power is 125 Vdc or 120 Vac, nominal
D--------Two current operated target indicators (one per function)
2--------Undervoltage element range 0.1 to 2.5 Vac (low range with sensing input 5)
S--------Push-to-energize outputs
3--------Two normally-open auxiliary output relays (one per function)
F--------Semi-flush mounting case

1-4 BE1-59N General Information 9171400990 Rev G
SPECIFICATIONS
BE1-59N electrical and physical specifications are listed in the following paragraphs.
Voltage Sensing Inputs
Maximum continuous rating: 360 Vac for 100/120 Vac input, 480 Vac for 200/240 Vac input, with a
maximum burden of 2 VA for each input.
Undervoltage Sensing Input Range
High Range: 0.5 to 12 Vac (sensing input range 1, 2, 5, or 6) or 1.0 to 24 Vac
(sensing input range 3, 4, 7, or 8).
Low Range: 0.1 to 2.5 Vac (sensing input range 1, 2, 5, or 6) or 0.2 to 5.0 Vac
(sensing input range 3, 4, 7, or 8).
Pickup Accuracy
1 to 24 Vac range: ±2% or 20 millivolts
All other ranges: ±2% or 10 millivolts
Overvoltage Sensing Input Range
Ranges selectable by unit type for 50 or 60 Hz operation: 1 to 20 Vac, 10 to 50 Vac, 2 to 40 Vac, 20 to
100 Vac.
Pickup Accuracy
120 Vac (sensing input range 1, 2, 5, or 6): ±2% or 100 millivolts, whichever is greater
240 Vac (sensing input range 3, 4, 7, or 8): ±2% or 200 millivolts, whichever is greater
Dropout
98% of pickup within 7 cycles.
Timing Characteristics
Instantaneous: Less than 70 milliseconds for a voltage level that exceeds the pickup
setting by 5% or 1 volt, whichever is greater
Definite: Adjustable from 00.1 to 99.9 seconds, in steps of 0.1 seconds.
Accuracy is within 2% or 100 milliseconds, whichever is greater. (A
setting of 00.0 provides instantaneous timing.)
Inverse: Response time decreases as the difference between the monitored
voltage and the setpoint increases. The inverse time characteristics
switch is adjustable from 01 to 99 in 01 increments. Each position
corresponds to a specific curve except 00, which is instantaneous.
Accuracy is within ±5% or 25 milliseconds (whichever is greater) of
the indicated time for any combination of the time dial and within
±2% of the voltage magnitude or 100 millivolts (for the 120 Vac
sensing range) or 200 millivolts (for the 240 Vac sensing range)
(whichever is greater) from the actual pickup value. Inverse time is
repeatable within ±2% or 25 milliseconds (whichever is greater) for
any time dial or pickup setting. The characteristic curves are defined
in Figures 1-3 and 1-4.
Output Contacts
Resistive Ratings
120 Vac: Make, break, and carry 7 Aac continuously
250 Vdc: Make and carry 30 Adc for 0.2 s, carry 7 Adc continuously,
break 0.3 Adc
500 Vdc: Make and carry 15 Adc for 0.2 s, carry 7 Adc continuously,
break 0.3 Adc

9171400990 Rev G BE1-59N General Information 1-5
Inductive Ratings
120 Vac, 125 Vdc, 250 Vdc: Break 0.3 A (L/R = 0.04)
Power Supply
Power supply types and specifications are listed in Table 1-1.
Table 1-1. Power Supply Ratings
Type Nominal
Input Voltage Input Voltage Range Burden at Nominal
K (midrange) 48 Vdc 24 to 150 Vdc 3.4 W
125 Vdc 24 to 150 Vdc 3.6 W
J (midrange) 120 Vac 90 to 132 Vac 22.1 VA
L (low range) 24 Vdc 12 to 32 Vdc ∗3.5 W
48 Vdc 24 to 150 Vdc 3.4 W
Y (midrange) 125 Vdc 24 to 150 Vdc 3.6 W
250 Vdc 68 to 280 Vdc 3.7 W
Z (high range) 240 Vac 90 to 270 Vac 37.6 VA
∗Type L power supply initially requires 14 Vdc to begin operating. Once operating, the input voltage may
be reduced to 12 Vdc and operation will continue.
Target Indicators
Electronically latched, manually reset target indicators are optionally available to indicate closure of the
trip output contacts. Either internally operated or current operated targets may be specified. Internally
operated targets should be selected when normally closed (NC) output contacts are specified.
Current Operated Targets
Minimum Rating: 200 mA flowing through the trip circuit
Continuous Rating: 3 A
1 Second Rating: 30 A
2 Minute Rating: 7 A
Type Tests
Shock: Withstands 15 G in each of three mutually perpendicular planes
without structural damage or performance degradation.
Vibration: Withstands 2 G in each of three mutually perpendicular planes,
swept over the range of 10 to 500 Hz for a total of six sweeps, 15
minutes each sweep, without structural damage or degradation of
performance.
Dielectric Strength: Tested in accordance with IEC 255-5 and IEEE C37.90: 2,000 Vac
applied for 1 min
Radio Frequency Interference: Field tested using a five watt, hand-held transceiver operating at
random frequencies centered around 144 MHz and 440 MHz, with
the antenna located six inches from the relay in both horizontal and
vertical planes.
Surge Withstand Capability: Qualified to IEEE C37.90.1-1989, Standard Surge Withstand
Capability (SWC) Tests for Protective Relays and Relay Systems.

1-6 BE1-59N General Information 9171400990 Rev G
Physical
Temperature
Operating Range: –40 to 70°C (–40 to 158°F)
Storage Range: –65 to 100°C (–85 to 212°F)
Weight: 13.6 lb (6.17 kg)
Case Size: S1 (See Section 4 for panel cutting/drilling dimensions.)
Agency Recognition/Certification
UL Recognition: UL recognized per Standard 508, File E97033
NOTE: Output contacts are not UL recognized for voltages greater
than 250 volts.
Gost-R Certification: Gost-R certified, No. POCC US.ME05.B03391; complies with the
relevant standards of Gosstandart of Russia. Issued by accredited
certification body POCC RU.0001.11ME05.
P0050-21
Voltage Difference from Pickup
Figure 1-3. Overvoltage Inverse Time Curves

9171400990 Rev G BE1-59N General Information 1-7
SCALE A 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2
SCALE B 4.8 4.4 4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 0.8 0.4
SCALE C 12 11 10 9 8 7 6 5 4 3 2 1
SCALE D 24 22 20 18 16 14 12 10 8 6 4 2
Voltage Difference from Pickup
Figure 1-4. Undervoltage Inverse Time Curves

1-8 BE1-59N General Information 9171400990 Rev G
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9171400990 Rev G BE1-59N Controls and Indicators 2-1
SECTION 2 •CONTROLS AND INDICATORS
INTRODUCTION
All BE1-59N controls and indicators are located on the front panel. The controls and indicators are shown
in Figure 2-1 and described in Table 2-1. Figure 2-1 illustrates a relay with the maximum number of
controls and indicators. Your relay may not have all of the controls and indicators shown and described
here.
P0050-21
A B
C
D
E
F
G
H
I
J
K
L
Figure 2-1. BE1-59N Controls and Indicators
Table 2-1. Control and Indicator Descriptions
Locator Description
A Overvoltage Pickup Adjustment. A multiturn potentiometer that sets the overvoltage
comparator threshold voltage. Continuously adjustable over the range indicated by the
style chart.
B Overvoltage Pickup LED. A red LED that illuminates when overvoltage exceeds the
pickup setting.
C Overvoltage Time Dial. Pushbutton switch that selects the desired overvoltage output
delay, either definite time (from 00.1 to 99.9 seconds) or, inverse time (characteristic
curves 01 through 99). A setting of 00 is instantaneous in either case.
D Undervoltage Time Dial. Pushbutton switch that selects the desired overvoltage output
delay, either definite time (from 00.1 to 99.9 seconds) or, inverse time (characteristic
curves 01 through 99). A setting of 00 is instantaneous in either case.

2-2 BE1-59N Controls and Indicators 9171400990 Rev G
Locator Description
E Power Indicator. This red LED lights when operating power is applied to the relay.
F Target Reset Switch. This switch is operated to reset the target indicators.
G Target Indicators. The electronically latched red target indicators illuminate when the
corresponding output relay energizes. To ensure proper operation of current-operated
targets, the current flowing through the trip circuit must be 200 mA or higher. Target
indicators are reset by operating the target reset switch (locator F).
H Output Test Pushbuttons. These pushbuttons allow manual actuation of the output relays.
Output relay actuation is achieved by inserting a nonconductive rod through the front
panel access holes.
I Undervoltage Pickup LED. A red LED that illuminates when undervoltage exceeds the
pickup setting.
J Undervoltage Pickup Adjustment. A multiturn potentiometer that sets the undervoltage
comparator threshold voltage. Continuously adjustable over the range indicated by the
style chart.
K Inhibit LED. A red LED that illuminates when the monitored generator voltage is under the
inhibit set point.
L Inhibit Pickup Adjustment. Multiturn potentiometer that sets the inhibit comparator
threshold so that whenever generator voltage falls below the set point, the (optional)
undervoltage measuring circuitry is inhibited from operation.

9171400990 Rev G BE1-59N Functional Description 3-1
SECTION 3 •FUNCTIONAL DESCRIPTION
INTRODUCTION
BE1-59N relay functions are illustrated in Figure 3-1 and described in the following paragraphs.
Figure 3-1. Function Block Diagram
INPUTS
The relay senses the level of voltage developed across a resistor connected in the neutral-grounding
transformer secondary. The relay may also be used with ungrounded systems with voltage transformers
connected in a wye/broken delta configuration. These connections are shown in Section 4.
Internal transformers provide further isolation and step down for the relay logic circuits.
FILTERS
A band-pass filter provides peak sensitivity at 50 or 60 Hz for the overvoltage input, with third harmonic
rejection of 40 dB minimum. If an undervoltage element is specified, an additional filter with peak
sensitivity at the third harmonic is included. The filter provides 40 dB rejection of the fundamental.
OVERVOLTAGE COMPARATOR
The overvoltage comparator circuit receives a sensing voltage from the band-pass filter and a reference
voltage from the front panel setting. The comparator determines within five cycles if the fundamental
frequency (50 or 60 hertz) is less than or greater than the reference setting. When the input exceeds the
setting, the resulting comparator output enables the timing circuit if definite or inverse time delay is
specified, and the OVERVOLTAGE PICKUP LED illuminates. If instantaneous timing is used, the
comparator output immediately energizes the overvoltage relay and, if present, the overvoltage auxiliary
relay.
DEFINITE TIME DELAY (OPTIONAL)
An output signal from the comparator circuit enables a counting circuit to be incremented by an internal
clock. When the counting circuit reaches a count, which matches the number entered on the TIME DIAL,
the output relay and auxiliary relay, if present, are energized. However, if the sensed input voltage falls
below the pickup setting before the timer completes its cycle, the timer resets within 2.0 cycles.

3-2 BE1-59N Functional Description 9171400990 Rev G
The definite time delay is adjustable from 00.1 to 99.9 seconds in 0.1-second increments. Front panel
mounted switches determine the delay. Position 00.0 is instantaneous.
INVERSE TIME DELAY (OPTIONAL)
The inverse time delay circuit is identical to the definite time delay circuit except that a voltage-controlled
oscillator (VCO) is substituted for the clock signal. The VCO, in turn, is controlled by a voltage derived
from the sensed input. Because the frequency of the oscillator is kept proportional to the sensed input
voltage, the desired inverse time delay is produced.
The inverse time characteristic curve switch is adjustable from 01 to 99 in 01 increments. Each position
corresponds to a specific curve setting except 00, which is instantaneous. Refer to Figure 1-2 to see the
inverse time characteristic curve.
REFERENCE VOLTAGE CIRCUIT
A constant voltage source provides a reference voltage to the potentiometers on the front panel. The
potentiometers, in turn, provide reference voltages to all the comparator circuits and establish the
threshold for each circuit.
UNDERVOLTAGE ELEMENT (OPTIONAL)
Undervoltage Operation
The undervoltage option is sensitive to the third harmonic voltage (150 Hz or 180 hertz) at generator
neutral, and provides 40 dB rejection of the fundamental frequency (50 or 60 hertz). The undervoltage
measuring element determines within five cycles if the third harmonic voltage is less than or greater than
the reference setting. If the measured third harmonic voltage is less than the reference setting, the
undervoltage pickup LED will illuminate, and the delay timer is triggered. When the timer completes its
cycle, a signal is generated to energize the undervoltage output relay and, if selected, the undervoltage
auxiliary relay. However, if the voltage level swings above the reference setting before the delay timer has
cycled, the output contacts reset within 7.0 cycles.
In the event that both trip conditions (undervoltage and overvoltage) are present, the undervoltage
response is inhibited.
The third harmonic pickup setting (i.e., UNDERVOLTAGE PICKUP) is a front panel mounted
potentiometer, continuously adjustable on the high range from 0.5 to 12 Vac (sensing input range 1, 2, 5,
or 6) or 1.0 to 24 Vac (Sensing input range 3, 4, 7, or 8). On the low range, it is adjustable from 0.1 to 2.5
Vac (sensing input range 1, 2, 5, or 6) or 0.2 to 5.0 Vac (Sensing input range 3, 4, 7, or 8). The time
delays available are instantaneous, definite, or inverse time. (Instantaneous is defined as no intentional
time delay. The timing circuits are analogous to those previously described.)
Undervoltage Inhibit
When the undervoltage measuring element is selected, an undervoltage inhibit circuit is included to
monitor the generator terminal voltage. This circuit inhibits operation of the 150/180 hertz measuring
element if the generator terminal voltage is less than the undervoltage inhibit setting. The panel mounted
undervoltage inhibit potentiometer is continuously adjustable from 40 to 120 Vac for 100/120 Vac sensing
input, and 80 to 240 Vac for the 200/240 Vac input.
OUTPUTS
Defined by the style number, the output relays may have either a normally open (NO) or normally closed
(NC) configuration. The normally open output contacts option is required when current operated targets
are desired.
In addition, auxiliary output contacts (1 for Over, 1 for Under) may be provided which are specified by
style number as NO or NC.
PUSH-TO-ENERGIZE OUTPUT PUSHBUTTONS
Small pushbutton switches may be provided as an option to allow testing the primary output contacts and
(if present) the auxiliary output contact. To prevent accidental operation, the pushbuttons are recessed
behind the front panel and are depressed by inserting a thin, non-conducting rod through an access hole
in the front panel.