Sel SEL-451-5 User manual

Schweitzer Engineering Laboratories, Inc. SEL-451-5-Based Autosynchronizer Data Sheet
A custom-engineered solution for safe,
secure autosynchronization of generation
onto the power system
Major Features and Benefits
SEL combines engineering services with the field-proven SEL-451-5 Relay for Advanced Autosynchronizing
(A25A) systems with the features and flexibility that customers have come to expect from SEL products and
systems. The SEL-451-5-based A25A is sold as a configuration and documentation disc. The user separately
purchases the SEL-451-5 Protection, Automation, and Bay Control System Relay per the Model Option Table
requirements detailed in this data sheet. Alternatively, the user can contact SEL Engineering Services to
obtain a fully engineered customized solution. Please refer to the SEL-451-5 data sheet for complete informa-
tion on the standard features available in this powerful device.
The pre-engineered A25A includes the following features:
➤Generator Frequency and Voltage Matching Control. Pulse governor and exciter reference points
to bring a generator into synchronism acceptance criteria. Pulse interval and pulse width parameters
are configurable for multiple synchronization situations. The control supports either fixed or propor-
tional pulse width control characteristics.
➤Breaker Close Delay Compensation. Issue a close signal in advance of zero degrees phase coinci-
dence so that the main contacts make as the generator phase angle difference reaches zero degrees.
➤Generator Frequency Greater Than Bus Frequency (GF > BF) (Antimotoring) Control. Apply in
situations with prime movers with extremely sensitive reverse power protection. The system requires
generator frequency greater than bus frequency to cause initial power flow to be out of the generator to
prevent trip of reverse power protection upon initial synchronization of the generator.
➤Dead-Scope Control. Generate a frequency raise pulse to prevent a near-zero slip-rate condition in
which two systems move very slowly relative to one another and take a long time to rotate into phase.
➤Generator Voltage Greater Than Bus Voltage (GV > BV) Control. Apply in situations where it is
necessary to prevent the generator from absorbing VARs from the system and pulling down the system
voltage on initial synchronization.
SEL-451-5-Based
Autosynchronizer

SEL-451-5-Based Autosynchronizer Data Sheet Schweitzer Engineering Laboratories, Inc.
2
➤Three-Close Conditions. Close the controlled circuit breaker under three conditions with specific
close acceptance criteria: autosynchronize close (phase angle is slipping), parallel close (zero slip con-
ditions), and live generator/dead-bus close.
➤Autosynchronize Acceptance Criteria. Initiate an autosynchronizing close when the generator fre-
quency difference, generator voltage difference, rate-of-change of frequency, and rate-of-change of
voltage are within user-defined parameters. Enable rate-of-change permissives separately to prevent
initiating an autosynchronize close operation when the frequency and voltage are still changing.
➤Parallel Close Acceptance Criteria. Initiate a parallel close when zero slip is detected and the angle,
voltage, and frequency are within acceptable limits. This is often used in dual breaker applications to
close the second synchronizing breaker after the generator has already been synchronized. This per-
missive can be disabled.
➤Dead-Bus Close Acceptance Criteria. Energize a dead bus from the generator in black-start applica-
tions. When the dead-bus close permissive input on the autosynchronizer is energized, the control
checks that the generator voltage and frequency are within acceptable limits and that the bus is dead
and then closes the synchronizing circuit breaker. This permissive can be disabled.
➤Operator Close Permissive. Implement multiple-level close supervision schemes by using the opera-
tor close permissive function. When operator close permissive is enabled, the operator must close the
operator close permissive contact inside the operator close permissive window in addition to meeting
all other close acceptance criteria. This permissive can be disabled.
➤Two Synchronizing Process Initiation Modes. Start and stop the autosynchronization process by one
of two modes: by selecting and deselecting the circuit breaker or by using initiate and abort controls.
➤Easy-to-Tune Settings. Simply set an interval for correction pulses and set slope or duration based
upon observed response rate of generator controls.
➤Digital Relay-to-Relay Communications. Use MIRRORED BITS®communications over fiber-optic
links to control breakers remote from the A25A device or to locate the A25A device remote from the
generator control room. The standard control features Port 3 configured for MIRRORED BITS with gen-
erator control pulse output contacts so that the control can be located remotely from the generator con-
trol room. Add an SEL-2505 Remote I/O Module (or other MIRRORED BITS-capable device with the
appropriate fiber-optic adapter and fiber cable) to locate the synchronizer close to the controlled syn-
chronizing breaker and synchronizing PTs. The remote I/O (RIO) can be located at the generator
exciter and governor. This feature is ideal for cogeneration applications where the cogenerator can
operate with critical load islanded from the grid and needs to be synchronized back to the grid after a
disturbance. Many other configurations are possible with customization. See the SEL-451-5 Data
Sheet for more information on MIRRORED BITS.
➤Advanced Communications Options. Easily integrate into your existing control system with serial or
optional Ethernet communications by using SEL, DNP3, and/or IEC 61850 protocols.
➤Oscillography and Sequence of Events Recording. Record current and voltage waveforms to ana-
lyze operation of each autosynchronization operation. Record sequence of events for binary status
points for fine-tuning autosynchronization system operation and getting to the root cause of distur-
bances.
➤Close Fail Alarm. Alert personnel if the controlled circuit breaker fails to close, within a user-config-
urable time and angle window, when a close command is issued.
➤Close Lockout Alarm. Alert personnel if the controlled circuit breaker opens within a user-configu-
rable time after a close.
➤Too Much Time Alarm. Automatically abort the synchronizing process if a close does not occur
within a maximum allowed time to synchronize. This function can be disabled.
➤Synchronization Operational Parameters Displayed. Troubleshoot and optimize the autosynchroni-
zation operation, using generator frequency and voltage data recorded for the most recent eight correc-
tion pulses. The elapsed time of autosynchronization operation is also displayed.

Schweitzer Engineering Laboratories, Inc. SEL-451-5-Based Autosynchronizer Data Sheet
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➤Optional Second I/O Board. When the optional second I/O board is ordered, the control includes
high-current interrupting contacts for generator frequency and voltage raise and lower contacts. It also
includes contacts for remote annunciation of front-panel indications such as SLIP OK, VOLTAGE OK, and
ANGLE OK and remote annunciation of Close Fail and Close Lockout alarms.
➤Custom ACSELERATOR QuickSet®SEL-5030 Software Settings Interface. Easily set the autosyn-
chronizer by using the provided settings template, which hides all of the settings for unused features of
the SEL-451-5 Relay and organizes all the user settings required to configure autosynchronizer fea-
tures.
➤Settings Groups for Five Generator/Breakers. Use in applications requiring as many as five inde-
pendent generator/breaker combinations.
➤Unprecedented Flexibility. With SEL Engineering Services customization, control multiple genera-
tors and/or multiple synchronizing breakers without the need for complicated synchronizing switch
circuits to route voltage transformer and control signals. Six independent single-phase voltage inputs
with two selectable master frequency-tracking inputs and multiple settings groups allow flexibility.
Ordering Information
Configuration and Documentation
Disc
The pre-engineered system configuration and documen-
tation disc can be ordered using part number
9163X451ASCD. The disc shown in Figure 1 includes a
QuickSet template that provides a customized user inter-
face for setting up the SEL-451-5 Relay as an A25A. It
also includes a detailed instruction manual and logic dia-
grams documenting the features, application, and pro-
gramming of the A25A.
Figure 1 Configuration and Documentation Disc
End users who purchase a configuration and documenta-
tion disc can use it to configure as many SEL-451-5
relays as needed for use on their power system facilities.
Use of the disc to configure advanced autosynchronizers
for other end users without permission from SEL is pro-
hibited.
SEL-451-5 Model Option Table
The autosynchronizer system requires an SEL-451-5,
purchased separately. The pre-engineered system is con-
figured as a fixed, single-function device with all inputs
and outputs (I/O) preassigned as described in Typical
Connections on page 10.
The SEL-451-5 is available in two standard configura-
tions: a three-rack unit version with standard I/O or a
four-rack unit version with a second I/O board. The stan-
dard autosynchronizer configuration requires a part num-
ber per the model option table (MOT) indicated in
Table 1. See Typical Connections on page 10 for more
information on the features the optional I/O board pro-
vides.
Custom Engineered Systems
The power and flexibility of the SEL-451-5 allow SEL
Engineering Services to customize the programming to
build advanced synchronizing systems. In many cases,
this can be more economical than designing and testing
complex synchronizing switching circuits. In other cases,
customization can create synchronizing systems that are
simply not possible to obtain from conventional technol-
ogy. See Application Examples on page 14 for more
information on possibilities. Contact SEL Engineering
Services to discuss whether the pre-engineered system is
right for your application or for a proposal on a custom
engineered system.

SEL-451-5-Based Autosynchronizer Data Sheet Schweitzer Engineering Laboratories, Inc.
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Note 1: Select option per requirements of the installation.
Note 2: Select Option 1 or 5 per requirements of the installation.
Note 3: The pre-engineered automatic synchronizer does not include configuration of these communications protocols.
Note 4: Select Option 1X if standard I/O is required. Select Option 27 if the second I/O board is required. See Table 3 for
additional features provided with the second I/O board.
Figure 2 Rear Panel of SEL-451-5 With Standard I/O (a) and With Optional Second I/O Board (b)
Table 1 Pre-Engineered Autosynchronizer Model Option Table Requirements
Position 123456789101112131415161718192021
Selection04515 X X XX X
Notes 112 33 11441 1
(a) (b)

Schweitzer Engineering Laboratories, Inc. SEL-451-5-Based Autosynchronizer Data Sheet
5
Control Functions
Successfully synchronizing a generator requires that
three parameters be within close acceptance criteria.
➤Slip (frequency difference) in acceptance band
➤Voltage difference in acceptance band
➤Angle difference near zero
The heart of an autosynchronizer is the slip-compensated
advanced angle close function that compensates for the
breaker mechanism delay and energizes the synchroniz-
ing breaker close coil at the precise instant to cause the
main contacts to make contact at zero degrees angle dif-
ference.
Additionally, the A25A has features to control the gener-
ator to match frequency and voltage by pulsing the refer-
ence points of the governor and voltage regulator
controls, respectively, to bring these parameters into the
synchronizing acceptance bands.
Start Sync Process Mode
Before a circuit breaker can be closed, the circuit breaker
must be selected by asserting one of the circuit breaker
selection inputs on the back of the control. Selecting a
breaker loads all the settings associated with that breaker.
One of two modes can be used to initiate the synchroniz-
ing process.
Start/Stop on Initiate and Abort Mode
When Start/Stop on Initiate and Abort mode is enabled,
the operator must select a circuit breaker for autosyn-
chronization. The synchronizing close process can be
initiated, or the circuit breaker can be closed by initiating
the autosynchronizer when one of the three close permis-
sive conditions is asserted (synchronizing close, parallel
close, dead-bus close).
Start/Stop on Circuit Breaker Selected Mode
When Start/Stop on Circuit Breaker Selected mode is
enabled, the operator must select a circuit breaker for
autosynchronization. The circuit breaker will close
immediately, or the autosynchronizing process will start
when one of the three close permissive conditions
asserts.
Frequency Matching
The A25A can adjust the generator frequency to match
the frequency of the bus. When isolated from the system,
the governor control operates in isosynchronous (fre-
quency control) mode. The control raises or lowers the
frequency reference point on the governor control via
pulsing contacts. The user can select between OFF, Fixed
Pulse Mode, and Proportional Pulse Mode.
Figure 3 shows the proportional pulse control character-
istic when the GF > BF (antimotoring) feature is enabled.
Figure 4 shows the control characteristic when the
GF > BF feature is disabled.
At zero slip, the generator angle will not rotate into phase
with the power system and a close cannot occur. When
GF > BF is not enabled, zero slip is inside the control
dead band, and no correction pulses will be sent to the
governor to change the slip rate off of zero. Figure 4
shows that the proportional pulse characteristic is modi-
fied by addition of a dead-scope band. If the frequency is
within the dead-scope band of ±20 mHz, a frequency
raise correction pulse will be output to move the slip rate
off of zero.
The following user settings define the control
characteristic:
➤Slip allowed (hertz)
➤Pulse width (seconds) (fixed pulse mode)
➤Proportional pulse slope (seconds/hertz) (propor-
tional pulse mode)
➤Pulse interval (seconds)
➤Enable/disable GF > BF
The pulse interval defines the time between the rising
edges of consecutive correction pulses. This time should
be greater than the settle time of the generator frequency
after each correction pulse.
The width of each correction pulse is proportional to the
deviation of the frequency from the center of the correc-
tion dead band when Proportional Pulse Mode is
enabled. As the frequency approaches the center of the
dead band, the correction pulses become shorter to pre-
vent hunting.
When GF > BF is enabled, the control ensures that the
allowable slip is positive (generator frequency greater
than bus frequency) so that power flow is out of the gen-
erator upon initial synchronization. This feature is rec-
ommended for applications that have prime movers with
extremely sensitive reverse power protection. The center
of the dead band is offset in the positive direction from
zero slip by one half of the slip allowed setting.
The correction dead band is fixed with a 20 percent mar-
gin inside the slip allowed synchronism acceptance set-
ting.

SEL-451-5-Based Autosynchronizer Data Sheet Schweitzer Engineering Laboratories, Inc.
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Figure 3 Proportional Frequency Correction Pulse Characteristic With GF>BF Enabled
Figure 4 Proportional Frequency Correction Pulse Characteristic With GF>BF Disabled
Voltage Matching
The A25A can adjust the generator voltage to match the
voltage of the bus. When isolated from the system, the
voltage regulator control operates in voltage control
mode. The control raises or lowers the voltage reference
point on the exciter control via pulsing contacts. The user
can select between OFF, Fixed Pulse Mode, and Propor-
tional Pulse Mode.
Figure 5 shows the proportional pulse control character-
istic when the GV > BV feature is enabled. Figure 6
shows the control characteristic when the GV > BV fea-
ture is disabled. The GV > BV control is used when you
want to ensure that the generator does not draw VARs
from the system upon initial synchronization to the bus.
The following user settings define the control character-
istic:
➤Voltage difference allowed (per-unit volts)
➤Pulse width (seconds) (fixed pulse mode)
➤Proportional pulse slope (seconds/per-unit volts)
(proportional pulse mode)
➤Pulse interval (seconds)
➤Enable/disable GV > BV
Gen. Frequency < Bus Frequency Gen. Frequency > Bus Frequency
Correction Dead Band
20% Slip Allowed
Gen. Frequency = Bus Frequency
80% Slip Allowed
Proportional Pulse
Slope Setting,
Seconds/Hertz
Seconds
Proportional Correction Pulse Range, ±400% Slip Allowed
Raise Gen. Freq. Pulse Width
Slip Allowed
Hertz
Lower Gen. Freq. Pulse Width
Correction Deadband
Hertz
Lower Gen. Freq. Pulse Width
Raise Gen. Freq. Pulse Width
+ Slip
Allowed
- Slip
Allowed
±80% Slip Allowed
Gen. Frequency < Bus Frequency Gen. Frequency > Bus Frequency
Seconds
Proportional Pulse
Slope Setting,
Seconds/Hertz
Proportional Correction Pulse Range, ±400% Slip Allowed
Gen. Frequency = Bus Frequency
±0.20 Hz Dead-Scope Band

Schweitzer Engineering Laboratories, Inc. SEL-451-5-Based Autosynchronizer Data Sheet
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The pulse interval defines the time between the rising
edges of consecutive correction pulses. This time should
be greater than the settle time of the generator voltage
after each correction pulse.
The width of each correction pulse is proportional to
deviation of the voltage from the center of the correction
dead band when Proportional Pulse Mode is enabled. As
the voltage approaches the center of the dead band, the
correction pulses become shorter to prevent hunting. The
correction dead band is fixed with a 20 percent margin
inside the voltage difference allowed synchronism accep-
tance setting.
Figure 5 Proportional Voltage Correction Pulse Characteristic With GV>BV Enabled
Figure 6 Proportional Voltage Correction Pulse Characteristic With GV>BV Disabled
Gen. Voltage = Bus Voltage
Correction Dead Band
PU Volts
Raise Gen. Voltage Pulse Width Lower Gen. Voltage Pulse Width
Proportional Correction Pulse Range, ±400% Voltage Difference Allowed
Gen. Voltage < Bus Voltage Gen. Voltage > Bus Voltage
Proportional Pulse
Slope Setting,
Seconds/PU Volt
±80% Voltage Difference Allowed
+Voltage
Difference
Allowed
-Voltage
Difference
Allowed
Seconds
Gen. Voltage = Bus Voltage
Correction Deadband
PU Volts
Raise Gen. Voltage Pulse Width Lower Gen. Voltage Pulse Width
Proportional Correction Pulse Range, ±400% Voltage Difference Allowed
Gen. Voltage < Bus Voltage Gen. Voltage > Bus Voltage
Proportional Pulse
Slope Setting,
Seconds/PU Volt
80% Voltage Difference Allowed
Voltage
Difference
Allowed
Seconds

SEL-451-5-Based Autosynchronizer Data Sheet Schweitzer Engineering Laboratories, Inc.
8
Synchronism Acceptance Criteria
Synchronizing close acceptance criteria include the fol-
lowing:
➤Slip allowed (Hz)
➤dF/dt allowed (Hz/second or OFF)
➤Voltage difference allowed (per-unit volts)
➤dV/dt allowed (per-unit V/second or OFF)
The system initiates a close at the slip-compensated
advanced angle as soon as the acceptance criteria are sat-
isfied. The optional rate-of-change checks prevent the
system from initiating a close operation when the fre-
quency and voltage are still changing.
Parallel Close Acceptance Criteria
For a parallel close scenario, the generator is already syn-
chronized to the system as determined by the absence of
a detectable slip. Often, a parallel close scenario occurs
when you want to close a second synchronizing breaker
via the autosynchronizer in a double-breaker bus
arrangement (ring bus, breaker-and-a-half bus, or double
bus double breaker) after the generator has already been
synchronized.
For a parallel close scenario, the breaker can be closed
immediately without waiting for frequency and voltage
matching processes to occur and the angle to slip towards
zero. So, the breaker is closed immediately if the parallel
close acceptance criteria are satisfied.
➤Generator and bus frequency are within the healthy
acceptance band
➤Generator and bus voltage are within the healthy
acceptance band
➤Angle is within the parallel close permissive win-
dow
This permissive can be disabled if parallel closing via the
A25A is not required.
Dead-Bus Close Acceptance
Criteria
Dead-bus close acceptance criteria include the following:
➤Generator frequency is within the healthy accep-
tance band
➤Generator voltage is within the healthy acceptance
band
➤Bus voltage is within the dead acceptance band
➤Operator dead-bus permissive input is asserted
The autosynchronizer monitors single-phase voltage
transformer (VT) inputs for generator and bus voltage
sensing. Thus, it cannot discern between a dead bus and a
blown VT fuse. To prevent an out-of-synchronization
close via the dead-bus permissive path when a VT fuse
blows, the dead-bus close acceptance criteria require an
operator to assert the dead-bus close enable input to con-
firm that a dead-bus close is necessary.
This permissive can be disabled if dead-bus closing via
the A25A is not required.
Operator Close Permissive
In some applications, a human operator should also agree
that it is safe to close the breaker before the synchroniz-
ing close output is asserted. When operator close permis-
sive is enabled, the operator must close the operator close
permissive contact inside the operator close permissive
window in addition to meeting all other close acceptance
criteria. This option requires either the optional second
I/O board or a remote I/O module to provide the operator
close permissive input to the A25A.
The characteristic of the operator close permissive is
shown in Figure 7. The slip-compensated advance angle
for a generator fast condition is the hatched area shown
in Figure 7. The operator close window is the black area
shown in Figure 7. The advanced angle and the operator
close window would be on the opposite side of zero
degrees for a generator slow condition.
If the operator closes the permissive contact outside of
the operator close permissive window, the close output is
locked out until the generator angle passes through and
back out of the synchronism-check angle window. This
feature prevents operators from taking themselves out of
the control loop by simply holding the control switch in
the closed position and letting the A25A perform the
close.
Figure 7 Operator Close Permissive Window
Fast
Slow
Parallel Close Window
Slip-Compensated
Advance Angle
Operator Close
Permissive Window

Schweitzer Engineering Laboratories, Inc. SEL-451-5-Based Autosynchronizer Data Sheet
9
Compensated Close Control
Independently configure the close mechanism delay for
as many as five controlled circuit breakers. As the phase
angle difference between the two systems closes toward
0 degrees, the close signal asserts in advance of 0 degrees
according to the measured slip rate and the breaker close
mechanism delay, so that the main contacts make contact
at precisely the instant when the phase angle between the
two systems is zero.
Close Success Monitoring
Once the automatic synchronizer is initiated, the syn-
chronizing process continues until one of the following
things happens:
➤The selected circuit breaker closes
➤The process is manually aborted by the operator
➤The breaker is deselected
➤The maximum time allowed to synchronize the
timer expires (if the function is enabled)
➤A close is attempted and the breaker fails to close,
asserting the Close Fail alarm
There are three close failure alarm functions.
Close Fail Alarm
A Close Fail alarm asserts if the system attempts an auto-
matic close and the selected circuit breaker fails to close.
The system latches this alarm in nonvolatile memory;
you must reset this alarm before you can attempt another
automatic close of that circuit breaker.
Close Lockout Alarm
A Close Lockout alarm asserts if a circuit breaker opens
within a time you define after an automatic close occurs.
The system latches this alarm in nonvolatile memory;
you must reset this alarm before you can attempt another
automatic close of that circuit breaker.
Maximum Time Allowed Alarm
The Maximum Time Allowed to Synchronize alarm
asserts if the close acceptance criteria are not met, mean-
ing that a close attempt can be initiated within the
allowed time. The system latches this alarm in nonvola-
tile memory; you must reset this alarm before you can
attempt another automatic close of that circuit breaker.
This alarm can be disabled.
Antipump (One Close Attempt Allowed) Logic
Once an automatic close has been initiated, a latch is set
that blocks any additional close attempts. The latch is
automatically reset when the breaker is deselected.

SEL-451-5-Based Autosynchronizer Data Sheet Schweitzer Engineering Laboratories, Inc.
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Typical Connections
Note 1: Synchronizing switch contacts for switching VT and I/O connections for the five generators are not shown for
simplicity.
Note 2: A user setting defines whether CB Status contact is 52A or 52B.
Note 3: The contact sensing input debounce parameters are configured for application with either ac or dc wetting
voltage. When using dc wetting voltage, observe polarity marks.
Note 4: If the optional second I/O board is ordered and high-current interrupting contacts are required for Raise and
Lower outputs, the terminal numbers change from starting with “A” to starting with “B” and the output contact
numbers change from 1xx series to 2xx series. The optional high-current interrupting contacts are polarity-sensitive,
with the lower number terminal as the “+” terminal.
Figure 8 A25A Typical Connection Diagram
VAY
VBY
VCY
VAZ
VBZ
VCZ
SEL-451-5
25A
VA
Generator
Synchronizing
Circuit Breaker
BUS
VA
Z13
Z14
Z15
Z16
Z17
Z18
Z19
Z20
Z21
Z22
Z23
Z24
A01
A02
OUT
101
A07
A08
OUT
104
A09
A10
OUT
105
A12
A13
OUT
106
A15
A16
OUT
107
Raise Frequency
Lower Frequency
Raise Voltage
Lower Voltage
Close
A20
A21
IN
101
52A or 52B
A22
A23
IN
102
A24
A25
IN
103
A26
A27
IN
104
A28
A29
IN
105
A30
A31
IN
106
+
+–
+–
+
+
+
+
+
A32
IN
107
+
+
Select
Breaker 1
Select
Breaker 2
Select
Breaker 3
Select
Breaker 4
Select
Breaker 5
Enable Dead-
Bus Close
VCVB VCVB
Note 1
Note 1
Note 1
Note 2
Note 1
Note 1
Note 4
Note 3

Schweitzer Engineering Laboratories, Inc. SEL-451-5-Based Autosynchronizer Data Sheet
11
Table 2 shows a complete listing of input and output functions for the standard I/O board.
Table 3 shows a complete listing of input and output functions for the optional second I/O board.
Table 2 I/O for Standard I/O Board
Outputs Function Inputs Function
OUT101a
aHigh-current interrupting contact.
Close IN101 Select Breaker 1
OUT102aIN102 Select Breaker 2
OUT103aClose Fail/Lockout IN103 Select Breaker 3
OUT104 Raise Frequency IN104 Select Breaker 4
OUT105 Lower Frequency IN105 Select Breaker 5
OUT106 Raise Voltage IN106 CB Status 52A or 52B
OUT107 Lower Voltage IN107 Enable Dead-Bus Close
OUT108 Self-Test Fail Alarm
Table 3 I/O for Optional Second I/O Board
Outputs Function Inputs Function
OUT201a
aHigh-current interrupting contact.
IN201 Alarm Reset
OUT202aIN202
OUT203aIN203
OUT204aRaise Frequency IN204
OUT205aLower Frequency IN205
OUT206aRaise Voltage IN206 Abort Synchronizing Process
OUT207aLower Voltage IN207 Initiate Synchronizing Process
OUT208aIN208 Operator Close Permissive
OUT209aVoltage OK to initiate
OUT210aFrequency OK to initiate
OUT211aSlip OK
OUT212aVoltage OK
OUT213aAngle OK
OUT214 Close Fail
OUT215 Close Lockout

SEL-451-5-Based Autosynchronizer Data Sheet Schweitzer Engineering Laboratories, Inc.
12
Table 4 shows a complete listing of input and output functions for the optional Remote I/O module connected via MIR-
RORED BITS. See the SEL-451-5 Data Sheet for more information on MIRRORED BITS.
User Interface
The user interface allows system operators to monitor the
autosynchronization process locally via the front panel of
the device. The control can be customized by SEL Engi-
neering Services to provide remote control and monitor-
ing via a communications interface or local control via
the front-panel pushbuttons.
Front-Panel HMI
The functionality of the front-panel LEDs and liquid
crystal display (LCD) indications are pre-engineered to
the functions shown in Figure 9 and Figure 10. The
labels are completely user-configurable. The configura-
tion and documentation disc includes label template files
that match the labeling shown in Figure 9 and Figure 10.
Users can easily modify these label files to provide appli-
cation-specific labels.
Figure 9 shows the front-panel layout of the control
pushbuttons and indicating LEDs when users enable
Start/Stop on Initiate/Abort mode for Start Synchroniz-
ing Process mode.
Figure 10 shows the front-panel layout of the control
pushbuttons and indicating LEDs when users enable
Start/Stop on CB Selected mode for Start Synchronizing
Process mode.
The control can be customized by SEL Engineering Ser-
vices to use the optional 12-pushbutton front panel, SEL
Fast Message communications, or any of the other avail-
able communications protocols to obtain remote access
to all control functions, metering, and status indications.
Figure 9 Front-Panel HMI Start Synchronizing Process
Mode Start/Stop on Initiate/Abort
Figure 10 Front-Panel HMI Start Synchronizing
Process Mode Start/Stop on CB Selected
The programmable LCD provides a summary of all criti-
cal parameters during the synchronizing process.
Figure 11 shows the information the 11-line LCD pro-
vides.
Ta b l e 4 I /O f o r M IRRORED BITS When Optional RIO Device Used
TMB Function RMB Function
TMB1A Voltage OK to initiate RMB1A Alarm Reset
TMB2A Frequency OK to initiate RMB2A
TMB3A Close Fail/Lockout RMB3A
TMB4A Raise Generator Frequency RMB4A
TMB5A Lower Generator Frequency RMB5A Enable Dead-Bus Close
TMB6A Raise Generator Voltage RMB6A Abort Synchronizing Process
TMB7A Lower Generator Voltage RMB7A Initiate Synchronizing Process
TMB8A RMB8A Operator Close Permissive
ENABLED
TRIP
FREQ. OK TO
INITIATE
GEN FREQ. HI
LOWER GEN
FREQUENCY
GEN FREQ. LO
RAISE GEN
FREQUENCY
SLIP OK
dF/dt OK
ANGLE OK
VOLTAGE OK TO
INITIATE
GEN VOLT. HI
LOWER GEN
VOLTAGE
GEN VOLT. LO
RAISE GEN
VOLTAGE
VOLTAGE
DIFFERENCE OK
dV/dt OK
ALARM, SEE LCD
CB 1
SELECTED
CB 2
SELECTED
CB 3
SELECTED
CB 4
SELECTED
CB 5
SELECTED
ABORT
SYNC
PROCESS
INITIATE
SYNC CL/
CB CLOSED
SELECTED
CB OPEN
ENABLED
TRIP
FREQ. OK TO
INITIATE
GEN FREQ. HI
LOWER GEN
FREQUENCY
GEN FREQ. LO
RAISE GEN
FREQUENCY
SLIP OK
dF/dt OK
ANGLE OK
VOLTAGE OK TO
INITIATE
GEN VOLT. HI
LOWER GEN
VOLTAGE
GEN VOLT. LO
RAISE GEN
VOLTAGE
VOLTAGE
DIFFERENCE OK
dV/dt OK
ALARM, SEE LCD
CB 1
SELECTED
CB 2
SELECTED
CB 3
SELECTED
CB 4
SELECTED
CB 5
SELECTED
SELECTED
CB CLOSED
SELECTED
CB OPEN

Schweitzer Engineering Laboratories, Inc. SEL-451-5-Based Autosynchronizer Data Sheet
13
Figure 11 Synchronizing Process Status Summary
Screen
The programmable LCD also provides a summary of the
generator frequency and voltage that the system recorded
for the most recent eight correction pulses. Figure 12 and
Figure 13 show the information the 11-line LCD pro-
vides. You can access these displays by pressing the
pushbuttons on the front of the control.
Figure 12 Frequency Matching Screen
Figure 13 Voltage Matching Screen
Customized QuickSet Settings
Template
A QuickSet template is provided with the autosynchro-
nizer system that gives the user a custom settings inter-
face, as shown in Figure 14. The template works inside
the QuickSet settings environment. This template orga-
nizes the settings for the autosynchronizer functionality
and hides most SEL-451-5 settings unused in the auto-
synchronizer control application.
Figure 14 QuickSet Template
SYNC STATUS
GEN FREQ XX.XXX HZ
BUX FREQ XX.XXX HZ
SLIP FREQ XX.XXX HZ
ANG DIF XXXX.X DEG
FREQ COR XXX PULSES
GEN VOLT XXX.XXX kV
BUS VOLT XXX.XXX kV
VLT DIF XXXX.XXX kV
VOT COR XXX PULSES
ELAPSD T XXX.X SEC
ROTATING DISPLAY
Press for menu
FREQ MATCHING DETAIL
FREQ COR XXX PULSES
dF/dt X.XXX HZ/s
G F N-0 XXX.XXX kV
G F N-1 XXX.XXX kV
G F N-2 XXX.XXX kV
G F N-3 XXX.XXX kV
G F N-4 XXX.XXX kV
G F N-5 XXX.XXX kV
G F N-6 XXX.XXX kV
G F N-7 XXX.XXX kV
ROTATING DISPLAY
Press for menu
VOLT MATCHING DETAIL
VOLT COR XXX PULSES
dV/dt X.XXX HZ/s
G V N-0 XXX.XXX kV
G V N-1 XXX.XXX kV
G V N-2 XXX.XXX kV
G V N-3 XXX.XXX kV
G V N-4 XXX.XXX kV
G V N-5 XXX.XXX kV
G V N-6 XXX.XXX kV
G V N-7 XXX.XXX kV
ROTATING DISPLAY
Press for menu

SEL-451-5-Based Autosynchronizer Data Sheet Schweitzer Engineering Laboratories, Inc.
14
Application Examples
SEL autosynchronization systems measure voltage and
frequency on both the generator and the power system,
send correction pulses to adjust the governor and exciter
as necessary, and automatically close the breaker, sepa-
rating the two systems once synchronization acceptance
criteria are met. This process ensures safe, secure auto-
synchronization of generation onto the power system.
Autosynchronization can reduce risk over manual syn-
chronization operations by ensuring that voltage differ-
ence and frequency difference (slip) are less than
maximum acceptance criteria and by closing the breaker
at the exact moment that the slipping systems come into
phase. Smooth synchronization reduces torsional stresses
to the generator and prime mover that cause accumulated
damage over the life of the generation system.
SEL autosynchronization systems are extremely flexible.
In addition to synchronizing a generator to the power
system, the system can also synchronize an islanded
power system back to the grid.
The following application examples are just a few of the
many configurations possible with SEL Engineering Ser-
vices customization. Contact the synchronizing experts
in SEL Engineering Services to discuss your application
requirements and get a proposal for an advanced syn-
chronizing system to improve reliability, reduce cost and
complexity, and improve operational flexibility.
Application Example 1: Synchronizing
Multiple Generators
Figure 15 shows a conventional autosynchronization
(25A) application example that uses the SEL system to
synchronize multiple generators. In this example, three
generators, two combustion-turbine generators (CT1 and
CT2), and one steam-turbine generator (ST1) in a com-
bined cycle power plant are connected to a collector bus.
Device A25A provides automatic close control of circuit
breakers G1, G2, and G3.
Figure 15 Synchronizing Multiple Generators
Output contacts connected to the governor system raise
and lower frequency. Output contacts connected to the
exciter system raise and lower voltage. The advance
angle-compensated autosynchronized close contacts are
connected to the close circuit of the circuit breakers.
While the pre-engineered scheme can be used in this
application, the VT signals and control signals would
have to be routed through synchronizing switch or selec-
tor contacts. With SEL Engineering Services customiza-
tion, the synchronizing switching circuits can be
eliminated. The application is unconventional in that
SELOGIC®control equations provide all switching of VT
circuits, governor and exciter correction pulse outputs,
and circuit breaker close outputs, eliminating the need
for complicated and unreliable synchronizing switch wir-
ing.
In this application, you would select the correct VT sig-
nals for measurement of the generator and system fre-
quency and voltage in programmable logic from the six
available single-phase inputs. You can then add optional
I/O boards to the SEL-451-5 to control as many genera-
tors and generator breakers as necessary via separate out-
put contacts. This functionality, combined with the
extensive communications capabilities available with the
SEL-451-5, simplifies implementation of operation via a
computerized integration system.
Application Example 2: Synchronizing at
Multiple Locations
Figure 16 shows a custom application that uses a cogene-
ration system to ensure reliable power supply to a critical
industrial load bus, where loss of power can result in
severe safety issues or severe economic losses. In this
application, we simplify the diagram by not showing CT
connections.
SEL-451
TH
Utility
Grid
11
CT1
G1
TL
ST1
G3
CT2
G2
1
1
A25A

Schweitzer Engineering Laboratories, Inc. SEL-451-5-Based Autosynchronizer Data Sheet
15
Device 67-SEP, located at the critical load bus, includes
voltage and frequency elements as well as directional
overcurrent elements that separate the critical load bus
from the utility when the device detects a disturbance on
the utility supply. Device 25A-L (local), located in the
cogeneration control room, provides autosynchronization
control for circuit breaker (CB) G and CB TIE. Device
25A-R (remote), located at the utility tie substation some
distance away, provides autosynchronization control and
directional overcurrent protection for CB U.
To synchronize the generator to the system via CB G,
device 25A-L, located in the cogeneration control room,
measures the generator and system frequency and volt-
age from the generator voltage transformer (VT) and the
auxiliary bus VT, respectively. The device uses software
to select the appropriate VT inputs from the six available
single-phase inputs on the SEL-451-5 relay. No external
switching of VT signals is necessary. Output contacts for
raising and lowering frequency are connected to the gov-
ernor system. Output contacts for raising and lowering
voltage are connected to the exciter system. The advance
angle-compensated autosynchronizing close command is
directly connected to the close circuit of CB G.
Figure 16 Synchronizing at Multiple Locations
To synchronize the islanded critical load bus to the sys-
tem via CB TIE, device 25A-L measures the generator
and system voltages at the critical load bus VT and the
additional load bus VT, respectively. These signals are
connected to two single-phase VT inputs on the
SEL-451-5 relay. Device 67-SEP on CB TIE receives the
advance angle-compensated autosynchronization close
command via MIRRORED BITS Channel A. Alternatively,
you could use an SEL-2505 or SEL-2506 Remote I/O
Module for the remote close command if a MIRRORED
BITS-capable relay is not used at CB TIE.
Device 25A-R provides both directional overcurrent pro-
tection and autosynchronization functionality for CB U.
Thus, it measures three-phase voltage on the utility side
of CB U and single-phase voltage on the cogeneration
side of CB U. It sends frequency and voltage correction
pulses to device 25A-L via MIRRORED BITS Channel B
when you select CB U for autosynchronizing close.
Application Example 3: Dual Breaker Syn-
chronizer With RIO
Figure 17 shows a custom application where the high-
voltage substation and the generating station are physi-
cally separated and you want to maximize isolation of
the protection and control systems between the two facil-
ities. The A25A (SEL-451-5) is configured to autosyn-
chronize two breakers. The RIO (SEL-2505) is
configured to pass voltage and frequency correction
pulses from the A25A to the generator and pass operator
controls from the control room to the A25A.
Figure 17 Dual-Breaker Synchronizer With Fiber-Optic
Link Between High-Voltage Yard and Control Room
Separation
Breaker
Additional
Loads
Critical
Loads
Aux
Bus
SEL-451
GTH
SEL-451
67-SEP
SEL-351S
1
GEN
Utility
Grids
25A–L
1
1
11
1
3
25A–R
U
G
GTL
TIE
MIRRORED BITS B
MIRRORED BITS A
G
21
SEL-451
1 1
1
SEL-
2505
M
IRRORED
B
ITS
High-Voltage
Substation
Generating
Station

SEL-451-5-Based Autosynchronizer Data Sheet Schweitzer Engineering Laboratories, Inc.
16
Guideform Specification
The SEL Advanced Autosynchronization System, based on the SEL-451-5 microprocessor-based relay, shall provide
control, protection, monitoring, and automation. Relay self-checking functions shall be included. Specific requirements
are as follows:
➤Frequency Matching. The system shall provide
fixed or proportional pulse width frequency match-
ing outputs to bring the slip frequency within the
acceptance criteria.
➤Voltage Matching. The system shall provide fixed
and proportional pulse-width voltage matching
outputs to bring the generator voltage within the
acceptance criteria.
➤Easy Control Characteristic Parameters. The
system shall include independent settings for pulse
interval, proportional pulse slope or duration, and
synchronism acceptance band to configure the fre-
quency matching and voltage matching control
characteristics.
➤Antimotoring. The system shall have the capabil-
ity to optionally only allow synchronization when
the frequency of the generator is greater than the
frequency of the system.
➤Generator Voltage Greater Than Bus Voltage.
The system shall have the capability to optionally
only allow synchronization when the voltage of the
generator is greater than the voltage of the system.
➤Dead Scope. The system shall have the capability
to send a frequency correction pulse to the gover-
nor when a dead-scope (near zero slip) condition is
detected.
➤Operator Close Permissive. The system shall
have the capability to optionally restrict synchro-
nizing close unless an operator asserts a close com-
mand within a operator close permissive angle
window.
➤VT Sensing Selection. The system shall have the
capability of measuring six individual single-phase
voltage signals and of being programmed by SEL
Engineering Services to select appropriate syn-
chronizing sources and references from these sig-
nals via programmable logic equations without
external switching of VT circuits.
➤Control Binary I/O Selection. The system shall
have the capability of isolated control I/O for each
generator and breaker and of being programmed by
SEL Engineering Services to select appropriate I/O
without external switching of I/O circuits.
➤Control Characteristic and Synchronism
Acceptance Settings. The system shall be capable
of storing separate sets of settings for as many as
five generator and breaker combinations.
➤Synchronism Acceptance Criteria. The system
shall be capable of ensuring that the voltage differ-
ence, frequency difference, and optionally, the
rate-of-change of voltage and rate-of-change of
frequency meet acceptance criteria before an auto-
matic close operation is initiated.
➤Slip Compensated Advanced Angle Close Con-
trol. The system shall be capable of compensating
for breaker close mechanism delay and measured
slip rate to issue a close command so that the main
contacts of the circuit breaker make at the moment
that the two voltages come into phase.
➤Parallel Closing Control. The system shall be
capable of optionally closing a generator breaker
under zero slip conditions after the generator has
been synchronized to the system.
➤Dead-Bus Closing Control. The system shall be
capable of optionally closing a live generator onto
a dead bus.
➤Two Modes of Start Control. The system shall be
capable of controlling the synchronizing process
by using operator initiate and abort controls or by
simply selecting a breaker.
➤High-Interrupting Current Pulse Contacts. The
system shall optionally include governor and
exciter pulsing contacts capable of interrupting
10 Adc with L/R = 40 ms at 125 Vdc.
➤Data Recording. The system shall be capable of
recording the correction pulse duration and con-
trolled parameter for frequency and voltage match-
ing functions for the last eight correction pulses.
These data can be used to fine-tune the propor-
tional pulse control slope and interval settings
when commissioning the system. The system shall
also record the number of correction pulses and
elapsed time parameters for the synchronizing pro-
cess.
➤Relay-to-Relay Logic Communications. The sys-
tem shall be capable of communicating control
actions via a serial communications link to remote
I/O devices. The serial communications link shall
be suitable for operation via fiber-optic modems.
➤IRIG-B Time Input. The components of the sys-
tem shall include an interface port for either a stan-
dard or high-accuracy demodulated IRIG-B time-
synchronization input signal.
➤Environment. The components of the system shall
be suitable for continuous operation over a tem-
perature range of –40° to +85°C.
➤Communications. The components of the system
shall include four independent EIA-232 serial ports
for external communication.
➤PC Interface. The components of the system shall
be capable of being set by Microsoft®Windows®-
based graphical and ASCII terminal interfaces.

Schweitzer Engineering Laboratories, Inc. SEL-451-5-Based Autosynchronizer Data Sheet
17
➤IEC 61850 Ethernet Communication. The com-
ponents of the system shall be capable of providing
IEC 61850-compliant communication. The
IEC 61850 capability shall include GOOSE mes-
saging and defined logical node data points.
➤Distributed Network Protocol (DNP). The com-
ponents of the system shall be capable of incorpo-
rating certified DNP3 Level 2 Outstation protocol
and Ethernet DNP3 LAN/WAN communication.
➤Terminal Connectors. The components of the
system shall include the ability to remove the
screw-terminal block connectors from the back of
the relay to disconnect I/O, dc battery monitor, and
power without removing each wire connection.
➤Synchrophasors. The components of the system
shall provide high-accuracy synchrophasor data
that are compliant with the IEEE C37.118 synchro-
phasor data standard. The IEEE C37.118 synchro-
phasor data shall be supported on serial and
Ethernet ports of the relay. The relay shall provide
the capability to produce as many as five PMU data
configurations.
➤HMI Display. The components of the system shall
include custom configurable display information to
display status, analog quantities with units, user-
defined labels, and alarm information.
➤Reliability. The vendor shall supply the actual
measured mean time between failures (MTBF) for
the components of the system upon request.
➤Service. The components of the system shall
include no-charge technical support for the life of
the product.
➤Manufacturer. The components of the system
shall be manufactured in the U.S.A.
➤Conformal Coating. The components of the sys-
tem shall have optional conformal coating to pro-
tect the circuit boards from harsh environments.
➤Warranty Return. The vendor shall support a 72-
hour turnaround on all warranty repairs.
➤Warranty. The components of the system shall
include a ten-year, no-questions-asked warranty
for all material and workmanship defects. In addi-
tion, the warranty shall cover accidental customer-
induced damage.

SEL-451-5-Based Autosynchronizer Data Sheet Schweitzer Engineering Laboratories, Inc.
18
Specifications
Please refer to the product data sheet for the SEL-451-5 Protection, Automation, and Control System for front-panel and
rear-panel diagrams, relay dimensions, and additional specifications. This data sheet contains information on specific
features and functions provided in the pre-engineered advanced autosynchronizer system.
General
Station Identifier: ASCII 40 characters
Relay Identifier: ASCII 40 characters
Nominal System Frequency: 50, 60
Device Set Up
Start Synchronizing Process
Mode: I = start/stop on ini/abort S = start/stop on CB selected
Generator Voltage Display
Base: G = Generator voltage base B = Bus voltage base
Breaker Status Sense: 52A = closed when CB closed
52B = closed when CB open
Operator Close Permissive
Mode: N = Contact not required Y = Contact required to close
Maximum Time Allowed To
Synchronize: 1–120 Minutes 0 = Off
Enable RIO Module: N = RIO module not used
Y = RIO module used
Event Reporting
CT Ratio, Input W: 1–50000 turns
CT Ratio, Input X: 1–50000 turns
Sensing
Generator PT Ratio
(Input Y): 1–10000 turns
Generator Nominal Voltage: 20–200 secondary V
Scale Generator Voltage
Display by SQRT(3): Y, N
Bus PT Ratio (Input Z): 1–10000 turns
Bus Nominal Voltage: 20–200 secondary V
Scale Bus Voltage Display by
SQRT(3): Y, N
Initiate Autosync
Upper Frequency Limit: 45–65 Hz
Lower Frequency Limit: 45–65 Hz
Upper Voltage Limit: 0.8–1.2 per-unit V
Lower Voltage Limit: 0.8–1.2 per-unit V
Close Acceptance
Enable GF > BF: Y, N
Slip Frequency: 0.025–0.500 Hz
Rate-of-Change of
Frequency: 0.010–1.000 Hz/s 0 = Off
Enable GV > BV: Y, N
Voltage Difference: 0.01–0.50 per-unit V
Rate-of-Change of Voltage: 0.001–1.000 per-unit V/s
0 = Off
Enable Parallel Close
Permissive: Y, N
Parallel Close/Operator
Permissive Window: 3.0°–80.0°
Dead-Bus Voltage: 0.01–0.50 per-unit V
0 = Off
Breaker Close Time: 1.00–30.00 cycles
Control
Frequency Correction Pulse
Interval: 1.00–30.00 s 0 = Off
Frequency Correction Pulse
Mode: P = Proportional F = Fixed
Frequency Pulse Width: 0.01–100 seconds or seconds/Hz
Voltage Correction Pulse
Interval: 1.00–30.00 s 0 = Off
Voltage Correction Pulse
Mode: P = Proportional F = Fixed
Voltage Pulse Width: 0.01–100.00 seconds or seconds/V
per-unit
Close Alarms
Close Fail Time: 0.10–60.00 s
Close Fail Angle: 3.0°–80.0°
Close Lockout: 0.50–60.00 s

Schweitzer Engineering Laboratories, Inc. SEL-451-5-Based Autosynchronizer Data Sheet
19
Factory Assistance
We appreciate your interest in SEL products and services. If you have any questions or comments, please contact us at:
Engineering Services Division
Schweitzer Engineering Laboratories, Inc.
2350 NE Hopkins Court
Pullman, WA 99163-5603 U.S.A.
Tel: [phone]
Fax: [phone]
Internet: www.selinc.com
Email: [e-mail]

20
© 2009–2015 by Schweitzer Engineering Laboratories, Inc. All rights reserved.
All brand or product names appearing in this document are the trademark or registered
trademark of their respective holders. No SEL trademarks may be used without written
permission. SEL products appearing in this document may be covered by U.S. and Foreign
patents.
Schweitzer Engineering Laboratories, Inc. reserves all rights and benefits afforded under
federal and international copyright and patent laws in its products, including without lim-
itation software, firmware, and documentation.
The information in this document is provided for informational use only and is subject to
change without notice. Schweitzer Engineering Laboratories, Inc. has approved only the
English language document.
This product is covered by the standard SEL 10-year warranty. For warranty details, visit
www.selinc.com or contact your customer service representative.
*PDSAUTO-01*
SCHWEITZER ENGINEERING LABORATORIES
2350 NE Hopkins Court • Pullman, WA 99163-5603 USA
Phone: [phone] • Fax: [phone]
Internet: www.selinc.com • E-mail: in[email protected]om
SEL-451-5-Based Autosynchronizer Data Sheet Date Code 20151112