Basler BE1-25 User manual

12570 Route 143 •Highland, Illinois 62249-1074 USA
Tel [phone] •Fax [phone]
www.basler.com •[email protected]
Publication
9170200990, Rev Y
Jul 2019
BE1-25
Sync-Check Relay
Instruction Manual

WARNING: California's Proposition 65 requires special warnings for products that
may contain chemicals known to the state of California to cause cancer, birth defects or
other reproductive harm. Please note that by posting this Proposition 65 warning, we are
notifying you that one or more of the Proposition 65 listed chemicals may be present in
products we sell to you. For more information about the specific chemicals found in this
product, please visit https://www.basler.com/Prop65.

9170200990 i
BE1-25 Preface
Preface
This instruction manual provides information about the installation and operation of the BE1-25 Sync-
Check Relay. To accomplish this, the following information is provided:
•General information
•Controls and indicators
•Functional description
•Installation
•Testing
•Specifications
Note
Relays with a Type T power supply require a Contact Sensing Module,
which comes supplied with its own instructions, publication
9170206990.
Conventions Used in this Manual
Important safety and procedural information is emphasized and presented in this manual through
warning, caution, and note boxes. Each type is illustrated and defined as follows.
Warning!
Warning boxes call attention to conditions or actions that may cause
personal injury or death.
Caution
Caution boxes call attention to operating conditions that may lead to
equipment or property damage.
Note
Note boxes emphasize important information pertaining to installation
or operation.

ii 9170200990
Preface BE1-25
12570 State Route 143
Highland IL 62249-1074 USA
www.basler.com
[e-mail]
Tel: [phone]
Fax: [phone]
© 2019 by Basler Electric
All rights reserved
First printing: November 1985
Warning!
READ THIS MANUAL. Read this manual before installing, operating, or maintaining the BE1-25. Note
all warnings, cautions, and notes in this manual as well as on the product. Keep this manual with the
product for reference. Only qualified personnel should install, operate, or service this system. Failure to
follow warning and cautionary labels may result in personal injury or property damage. Exercise
caution at all times.
Basler Electric does not assume any responsibility to compliance or noncompliance with national code, local code,
or any other applicable code. This manual serves as reference material that must be well understood prior to
installation, operation, or maintenance.
For terms of service relating to this product and software, see the Commercial Terms of Products and Services
document available at www.basler.com/terms.
This publication contains confidential information of Basler Electric Company, an Illinois corporation. 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 interests of Basler Electric Company and used strictly for the purpose intended.
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. Over time, improvements and revisions may be made to this
publication. Before performing any of the following procedures, contact Basler Electric for the latest revision of this
manual.
The English-language version of this manual serves as the only approved manual version.

9170200990 iii
BE1-25 Contents
Revision History
A historical summary of the changes made to this instruction manual is provided below. Revisions are
listed in reverse chronological order.
Instruction Manual Revision History
Manual
Revision and Date
Change
Y, Jun-19
•Clarified Test Procedure, Step 1.
X, Apr-19
•Changed minimum voltage requirements for sync-check function
from 60V to 80V throughout manual
•
Minor text edits throughout manual
W, Oct-18
•Minor clarifications to style chart, S1 case cutout, and power
supply burden
V, Jun-15
•Updated manual to latest style
•
Minor text edits throughout manual
U, Jul-13
•Added Caution for contact sensing in Specifications
•Minor text and formatting edits
T, Oct-12
•Standardized case and cover drawings in Section 4
S, Mar-11
•Updated power supply burden data in Section 1
•Updated GOST-R statement in Section 1
•
Updated Storage Statement in Section 4
R, Sep-07
•Moved content of Section 6, Maintenance to Section 4
•Added manual part number and revision to all footers
•Updated power supply burden data in Section 1
•
Updated Target Indicator description in Section 3
Q
•This revision letter not used
P, Nov-06
•Updated Output Specs in Section 1
•Added footnote to Figures 1-2 and 1-3
•Updated drawings of case cover in Section 4, Installation
•Updated front panel drawing in Section 2, Controls and Indicators
•Moved manual Revision History to the front of the manual
•
Updated drawing on front cover
O
•This revision letter not used
N, Aug-02
•Updated drawings in the manual to label terminal 15 (COM) as
Vctrl
•
Corrected various minor errors throughout the manual
M, Feb-01
•Changed the Specifications, illustrations, and the descriptions
throughout the manual for the minimum voltage required to
operate the sync-check function
•Corrected Figure 1-6, Style Chart
•Added contact-sensing burden and enhanced Surge Withstand
Capability description
•Added new covers information
•Changed Section 5, Testing to reflect the minimum voltage
requirements for sync-check function

iv 9170200990
Contents BE1-25
Manual
Revision and Date
Change
L, Aug-98
•Added Power Supply information to Section 3 and added new wide
range power supply information to Section 1
•Corrected Style Chart by changing Power Supply Type T from 230
Vac to 240 Vac
•Moved Testing information from Section 4 to new Section 5,
Testing
•Added new outline dimensions to include all options (S1 Case,
Double-Ended, Semi-Flush, and Projection Mounting)
•Corrected ground symbol in Figure 4-7, Internal Diagram
•
Updated front cover and Manual Change information
K, Dec-97
•Deleted the reference to Service Manual 9170200620 on page 1-1
•Corrected an error found on page 1-11 in Minimum Voltage
Requirement from “45 ±2 Vac” to “80 Vac”
•Updated front cover and Manual Change information
J, Oct-97
•Added three new types (A, B, & C) to Option 2. This included new
paragraphs describing Average Detectors
I
•This revision letter not used
H, Jan-96
•Corrected power supply type P, voltage input, and range from Vdc
to Vac
•Minor page layout changes developed from using a word
processor application upgrade
G, Jan-95
•Reformatted instruction manual as Windows Help file for electronic
documentation
F, Mar-92
•Added new Figure 4-7, Internal Diagram and incorporated new
instruction manual format
E, May-90
•Edited General Information section and Controls and Indicators
section for clarification
•
Revised Figure 4-12 and edited Operational Test Procedure
D, Jul-88
•Added test plug/adapter information
•
Added TB2 terminal strip to connection diagrams
C, Jun-87
•Revised manual to reflect introduction of power supply status
option
B, Dec-86
•Added note to Style Chart
•Added footnote to power supply table and deleted the words make
and from inductive contact specification
•Corrected and clarified phase angle specifications
•
Corrected typographical errors on Slip Frequency graph
A, Nov-85
•Added information to Figures 4-4, 4-9, and 4-10
•Added storage recommendation paragraph

9170200990 v
BE1-25 Contents
Contents
Introduction.................................................................................................................................................1-1
Controls and Indicators..............................................................................................................................2-1
Functional Description................................................................................................................................3-1
Installation..................................................................................................................................................4-1
Testing........................................................................................................................................................5-1
Specifications.............................................................................................................................................6-1

vi 9170200990
Contents BE1-25

9170200990 1-1
BE1-25 Introduction
1 • Introduction
The BE1-25 is a solid-state synchronism check relay designed to permit breaker closure when the
desired maximum phase angle conditions have held for a specified minimum time. The maximum
allowable phase angle and time delay requirements can be set on front panel thumbwheel switches. Five
voltage measuring options are available that identify significant line and bus voltage conditions, and this
information is used to influence the relay output.
Application
BE1-25 Sync-Check Relays are recommended for situations that require verification of synchronism prior
to closing a circuit breaker. Typical applications are:
•Paralleling a generator to a system.
•Reestablishing a connection between two parts of a power system.
•Supervising fast transfer schemes, where fast pickup and dropout of the phase measuring circuit
are required.
If optional voltage measuring circuits are incorporated (Option 2), the BE1-25 can determine whether an
input is live, dead, or in an overvoltage state.
Sync-Check Function
BE1-25 Sync-Check function measures the phase angle between single-phase voltages of line and bus.
Then sync-check verifies that this angle is less than the front panel PHASE ANGLE selector setting. If the
measured angle has met these criteria for the time period defined by the front panel TIME DELAY setting,
the SYNC output contact closes.
Note
Sync-Check Voltage sensing circuits are guaranteed to operate at a
minimum voltage of 80 volts. They are guaranteed not to operate at
voltages less than 20 volts. Some units may operate at voltages in
between these two levels because of the individual characteristics of
specific components. Minimum voltage detection is usually in the
range of 45 to 55 volts.
The allowable phase angle is adjustable over the range of 1 to 99 degrees. The time delay is adjustable
over either of two ranges: 1 to 99 cycles, 50/60 hertz (using the bus frequency as the reference), or 0.1 to
99 seconds (using the internal crystal controlled oscillator as the reference).
An optional target may be specified to indicate operation of the Sync-Check function.
Contact Sensing
To control operation of the relay, an input from the breaker auxiliary 52b contact is required to signal the
breaker status. If the breaker is open, the relay is enabled to perform its function. When the breaker
closes, the 52b input changes state and causes the relay to terminate its close signal.
Two configurations of the 52b contact sensing input are available to provide additional flexibility for the
protection circuit designer:
•Isolated contact sensing monitors a current supplied by the relay through an isolated contact.
•Non-isolated contact sensing monitors the presence of voltage at its input due to the closure of a
contact.

1-2 9170200990
Introduction BE1-25
See the Installation chapter for typical control circuit connections for each configuration.
Voltage Monitor Options
Mode Switches
Two Mode switches are located on the Voltage Monitor card. Mode Switch No. 1 serves the bus Voltage
Monitor function. Mode Switch No. 2 serves the line Voltage Monitor function. Mode switch positions are
as follows:
NORMAL Mode (Up) - allows measuring elements to establish live and dead reference levels for
the input level.
NOT-OV Mode (Down) - allows measuring elements to establish live and Not-Overvoltage
reference levels for the input level.
When a Mode Switch is in the NORMAL Mode position (Up), a dead level is defined as a monitored
voltage level below the DEAD reference setting. See Figure 1-1 for voltage monitor acceptance zones. A
live level is defined as a monitored voltage above the LIVE reference setting.
When a Mode Switch is in the NOT-OV Mode position (Down), a dead level is defined as a monitored
voltage less than the LIVE reference setting, and a live level is defined as a monitored voltage greater
than the LIVE reference setting, but less than the NOT-OV setting. (An input is considered over-voltage
when it exceeds the NOT-OV reference setting.)
It is permissible to operate the line input in either the same mode or a different mode than the bus input.
This flexibility allows the BE1-25 to be used, for example, to close a generator breaker onto a dead bus,
or to prevent closure if the generator and/or bus voltage is too high.
See the Controls and Indicators chapter for a complete description and precautions on setting the Mode
Switches. The location of the switches is shown. Also, see Switch Settings, Condition and Mode Switches
in the Testing chapter.
Figure 1-1. Voltage Monitor Acceptance Zones

9170200990 1-3
BE1-25 Introduction
Condition Switches
Five Condition Switches are located on the Voltage Monitor Card, each with two positions to select ON
(Down) and OFF (Up). When ON, Condition Switch No. 1 programs the relay to require recognition that
the line and bus are not in an overvoltage condition (NOT OV) before the SYNC output is allowed.
Condition Switches No. 2 through No. 5 modify the voltage monitor response according to a programmed
set of external conditions. The possible external conditions for each of these four switches are:
Switch 2. Live Line/Live Bus (LL-LB)
Switch 3. Dead Line/Live Bus (DL-LB)
Switch 4. Live Line/Dead Bus (LL-DB)
Switch 5. Dead Line/Dead Bus (DL-DB)
When a selected condition has been recognized, the voltage monitor circuit may be instructed to
immediately energize the Sync-Check output relay, or (if provided) the Voltage Monitor output relay. (See
Figure 1-1, Note 1.)
See the Controls and Indicators chapter for a complete description and precautions on setting the
Conditions Switches. The location of the switches is shown.
Voltage Difference
A voltage monitor is available that checks the phasor or average voltage difference between the two
inputs. This can be used to prevent the closure of a generator breaker if the voltage difference is too great
(even if the phase angle and voltage level monitoring circuits indicate that proper closing conditions are
otherwise present).
The voltage difference option (included with option 2-A, 2-B, 2-C, 2-R, 2-T or 2-U) is typically used to
reduce the amount of possible system shock or transients when closing a breaker. This option compares
the voltage between line and bus against a selected limit, and initiates either an enable or an inhibit signal
for the sync-check logic, thereby narrowing the voltage across the breaker contacts (as compared to a
simple sync-check acting alone). Figure 1-2 shows closing zones obtained by combining phasor voltage
difference, phase angle limit, and line and bus live/dead voltage limits. Figure 1-3 shows closing zones
obtained by combining average voltage difference, phase angle limit, and line and bus live/dead voltage
limits.
Figure 1-2. Closing Zone (Phasor Sensing)

1-4 9170200990
Introduction BE1-25
Figure 1-3. Closing Zone (Average Sensing)
∗Lines apply only if using the NOT-OV mode setting. When operating in NORMAL mode, the 135V
(MAX) line applies as an upper limit.
Option 2-R, 2-T, or 2-U (Phasor Voltage Difference)
Figure 1-4 may be used as an aid in formulating the voltage difference control settings. Note that the
center reference phasor (
V
B
) represents the monitored bus voltage, while the adjacent phasor (
V
L
)
represents the monitored line voltage. The voltage difference control (∆V) forms an area of acceptance
limit when rotated through 360 degrees. This allows either the voltage difference or the phase angle to be
selected, and the remaining value to be calculated.
Calculate the voltage difference (∆V) using the law of cosines. The equation is:
∆V V V V V
L B L B
= + − ⋅ ⋅ ⋅(cos )
2 2
2
1
2
θ
Equation 1-1
When
VL
is tangent to the voltage difference circle, the ∆V phasor is perpendicular to
VL
at the phase
angle limit. Accordingly, the voltage difference or the phase angle can be calculated by equations 2 and
3, respectively.
∆V V sin
B
= θ
Equation 1-2
θ∆ =− sin V
V
1
B
Equation 1-3
where:
∆V = Voltage Difference
VL
= Line Voltage
VB
= Bus Voltage
θ= Phase Angle
Note that the point where
VL
is tangent to the voltage difference circle represents the most extreme
condition of θfor a closure. Assuming that a constant voltage difference exists, the following condition is
valid: If the magnitude of the line voltage decreases, the phase angle must also decrease to allow sync-
acceptance. Therefore, the minimum line voltage possible for sync-acceptance occurs at zero phase
angle.

9170200990 1-5
BE1-25 Introduction
Figure 1-4. Closing Zone Calculation Diagram (Phasor Sensing)
Option 2-A, 2-B, or 2-C (Average Voltage Difference)
This option is similar to option 2-T, 2-R, or 2-U except for the sensing method. This option provides
average voltage sensing instead of phasor voltage sensing. This provides a constant ∆V setting
independent of the phase relationship between the line and bus voltages.
Figure 1-5 may be used as an aid in formulating the voltage difference control settings. Note that the
center reference phasor (
VB
) represents the monitored bus voltage, while the adjacent phasor (
VL
)
represents the monitored line voltage. The voltage difference control (∆V) forms an area of acceptance
limit.
Figure 1-5. Closing Zone Diagram (Average Sensing)
Output Relay
The Voltage Monitor output relay option G or H provides additional supervision of the breaker closing
circuit, or provides an indication of the existing voltage conditions for the supervisory control system.
VLVB
P0004-37
θ
V
P0004-39
VB
L
V

1-6 9170200990
Introduction BE1-25
When a Voltage Monitor output relay is installed, the SYNC relay is no longer directly operable by voltage
monitor logic. However, the live line/live bus condition may be utilized to enable the Sync-Check function.
Detailed instructions and precautions for setting the Mode switches and Condition switches are provided
in the Controls and Indicators chapter. The location of the switches is shown.
Voltage sensing connections are shown in the Installation chapter.
Other Options
Expandable Window
An expandable window (option 9 in the second position of the Style Number) is available to enable a local
operator (through a switch) or a remote dispatcher (through the supervisory control system) to expand the
preset phase angle window by a programmed ratio.
Under normal conditions, the phase angle setting is determined by the maximum angular difference that
has been calculated as suitable to meet the expected load flow of the total system. However, under
emergency conditions, the load flow throughout the system may result in excessive phase angle
separation across the opened breaker.
In order to reestablish load on a previously faulted line quickly, it may be necessary to expand the
allowable phase window. With this option, closing a contact input to the relay expands the preset phase
setting by a programmed multiple of 2 or 3 (according to the position of a jumper on the circuit card).
This option is not suggested for use in generator applications for the following reason: The phase angle
setting for a generator breaker is determined by the maximum phase difference that can be tolerated by
the generator when connected to the system. An excessive angle can result in excessive mechanical
forces in the generator and associated mountings.
Internal connections for the expandable window along with control circuit connections are shown in the
Installation chapter.
External Condition Switches
If a line and bus Voltage Monitor output is incorporated in the relay, the internal Condition Switches may
be functionally operated by remotely located external contacts. This capability is provided by Voltage
Monitor option 2-C, 2-U, or 2-V, but requires a voltage dropping Resistor Module to be mounted on the
relay back panel (see the Installation chapter).
Push-to-Energize Output Pushbuttons
Two PUSH-TO-ENERGIZE OUTPUT switches are available to provide a means of verifying external
output wiring without the inconvenience of having to test the entire relay. These optional switches are
provided for each isolated output function (Sync-Check, Auxiliary Sync-Check and Voltage Monitor), and
may be actuated by inserting a thin, non-conducting rod through access holes in the front panel. See the
Controls and Indicators chapter for location.
Model and Style Number
The electrical characteristics and operational features of the BE1-25 Sync-Check Relays are defined by a
combination of letters and numbers that make up its Style Number. The model number, together with the
Style Number, describes the options included in a specific device, and appears on the front panel,
drawout cradle, and inside the case assembly.
Upon receipt of a relay, be sure to check the Style Number against the requisition and the packing list to
ensure that they agree.

9170200990 1-7
BE1-25 Introduction
Style Number Example
The Style Number identification chart (Figure 1-6) defines the electrical characteristics and operational
features included in BE1-25 relays. For example, if the Style Number were M9H-A6P-N4R0F, the device
would have the following:
BE1-25 Model Number (designates the relay as a Basler Electric, Class 100, Sync-Check Relay)
MSingle-phase sensing
9Expandable phase angle window
HVoltage Monitor relay and Push-to-Energize outputs
A6 0.1 to 99 seconds timing range
POperating power derived from 125 Vdc or 120 Vac
NNo target
4Non-isolated contact sensing input
RLine and Bus Voltage Monitor; also a Voltage Difference Monitor with Condition Switches
internal to the relay.
0No auxiliary output
FSemi-flush mounting
Figure 1-6. Style Number Identification Chart

1-8 9170200990
Introduction BE1-25

9170200990 2-1
BE1-25 Controls and Indicators
2 • Controls and Indicators
BE1-25 controls and indicators are located on the front panel and right-side interior. The controls and
indicators are shown in Figure 2-1 and Figure 2-2, and described in Table 2-1. Your relay may not have
all of the controls and indicators shown and described here.
Figure 2-1. Location of Controls and Indicators (Front Panel View)

2-2 9170200990
Controls and Indicators BE1-25
Figure 2-2. Location of Controls and Indicators (Interior View)
Table 2-1. Controls and Indicators
Callout
Control or Indicator
Function
A
SYNC Indicator
Red LED lights when an in-sync condition has been of
sufficient duration to match the TIME DELAY setting. Lighting
of the LED coincides with closure of the Sync Output contacts.
The LED extinguishes when 52b opens or the in-sync condition
ceases.
B
TIME DELAY Selector
Thumbwheel switches establish the time delay between
sensing the desired in-sync condition and closing the Sync
Output contact. Time delay is in units of seconds or of cycles,
according to the option selected.
Option A6: Adjustable in 1-second increments over a range of
01 to 99 seconds when multiplier switch (callout D) is in the X
1.0 position. Alternatively, the range is 0.1 to 9.9 seconds with
the multiplier switch in the X 0.1 position.
Option A7: Adjustable in 1-cycle increments from 1 to 99
cycles. The multiplier switch (callout D) is omitted.
Note
A setting of 00 will inhibit closing of the SYNC output.
C
POWER Indicator
LED lights to indicate that the relay power supply is functioning
properly.
D
TIME DELAY Multiplier
Switch
Explained above in B, TIME DELAY Selector.
P0046-05

9170200990 2-3
BE1-25 Controls and Indicators
Callout
Control or Indicator
Function
E
ΔV Indicator
Red LED lights when the difference between the bus and line
voltage is less than the ΔV setting.
ΔV Adjustment
Continuously adjustable from 1 to 135 Vac. Adjustment is by
small screwdriver through an access hole in the front panel.
CW rotation increases the voltage difference setting.
F
DL/NOT OV Indicator
When in the NORMAL Mode:
Red LED lights when the line voltage is less than the reference
voltage established by the DL/NOT OV setting that defines a
dead line.
When in the NOT OV Mode:
Red LED lights when the line voltage does not exceed the
reference voltage established by the DL/NOT OV setting that
defines an overvoltage condition.
DL/NOT OV Adjustment
Continuously adjustable over the range of 10 to 135 Vac.
Adjustment is by small screwdriver through an access hole in
the front panel. CW rotation increases voltage setting.
G
LL Indicator
Red LED lights when the line voltage exceeds the reference
voltage established by the LL setting.
LL Adjustment
Continuously adjustable from 10 to 135 Vac. Adjustment is by
small screwdriver through an access hole in the front panel.
CW rotation increases the voltage setting.
H
Target Reset Switch
Allows manual reset of the target.
I and J
PUSH-TO-ENERGIZE
OUTPUT Switches
Momentary pushbuttons are accessible by inserting a 1/8 inch
diameter non-conducting rod through access holes in the front
panel. Switch I, when actuated, closes the Sync Output
contacts and (if specified) the Auxiliary Sync Output contacts.
Switch J closes the (optional) Voltage Monitor Output contacts.
K
Target Indicator (Optional)
Electronically latching red indicator lights when the Sync
Output relay is or was energized.
L
LB Indicator
Red LED lights when bus voltage exceeds the reference
voltage established by the LB setting that defines a live bus
condition.
LB Adjustment
Continuously adjustable over a range of 10 to 135 Vac.
Adjustment is by small screwdriver through an access hole in
the front panel. CW rotation increases voltage setting.
M
V Indicator
Red LED lights whenever the (optional) Voltage Monitor Output
relay is energized.
N
DB/NOT OV Indicator
When in the NORMAL Mode:
Red LED lights when the bus voltage is less than the reference
voltage established by the DB/NOT OV setting that defines a
dead bus condition.
When in the NOT OV Mode:
Red LED lights when the bus voltage does not exceed the
reference voltage established by the DB/NOT OV setting that
defines an overvoltage condition.
DB/NOT OV Adjustment
Continuously adjustable over the range of 10 to 135 Vac.
Adjustment is by small screwdriver through an access hole in
the front panel. CW rotation increases the voltage

2-4 9170200990
Controls and Indicators BE1-25
Callout
Control or Indicator
Function
O
PHASE ANGLE Selector
Note
A PHASE ANGLE setting of 00 inhibits operation of
the relay.
Thumbwheel switches set the acceptable maximum phase
difference between the line and bus voltages. This phase
difference window is adjustable in 1 degree increments over a
range of 1 to 99 degrees.
P
PHASE ANGLE Indicator
Red LED lights when the phase angle is within the limits
established by the adjacent PHASE ANGLE Selector.
Q
Switchable jumper for
EXPAND option
Position of jumper in Figure 2-2 controls the width of the
expanded phase angle window as a multiple of the PHASE
ANGLE setting. The two positions are X2 and X3.
R
MODE Switch No. 1 (Bus)
and MODE Switch No. 2
(Line)
Up = NORMAL Mode
Down = NOT OV Mode
When in the NORMAL Mode:
1. A high voltage threshold is established by front panel
controls, above which the bus (or line, as the case may be)
is considered live.
2. A low voltage threshold is established by front panel
controls, below which the bus (or line) is considered dead.
When in the NOT OV Mode:
1. A voltage above the high voltage setpoint setting is
considered overvoltage.
2. A voltage below the low voltage setpoint setting is defined
as dead.
3. A voltage between the two setpoints is defined as live. This
condition is indicated by the illumination of two LEDs: either
LL or LB and the corresponding NOT OV.
S
CONDITION Switch
No. 1 (Not-Overvoltage
Enable to the sync logic
circuitry)
Up = OFF: Disables the NOT OV Mode of operation during a
live line/live bus condition.
Down = ON: Allows the NOT OV Mode of operation to add a
further constraint to the live line/live bus condition (assuming
that the NOT OV Mode has been previously selected on Mode
Switch No. 1 or No. 2). The additional constraint is that the line
and/or bus must not be in the overvoltage region. (This switch
does not affect the Voltage Monitor Output relay.)