Schweitzer Engineering Laboratories SEL-787-3 User manual

Schweitzer Engineering Laboratories, Inc. SEL-787-3, -4 Data Sheet
Major Features and Benefits
The SEL-787 Transformer Protection Relay provides unsurpassed protection, integration, and control features in a
flexible, compact, and cost-effective package. The SEL-787 offers an extensive variety of protection features, depending
on the model and options selected. In this document, SEL-787 refers to all the models in Table 1. For protection func-
tions specific to a given MOT, the relay is referred to as SEL-787-4X, SEL-787-3E, or SEL-787-3S explicitly, where
needed. Model options SEL-787-4X, SEL-787-3E, and SEL-787-3S are all considered base models. Table 2 shows the
protection features available across different models.
SEL-787-3E Model SEL-787-3S Model SEL-787-4X Model
Table 1 Current (ACI) and Voltage (AVI) Card Selection for SEL-787 Models
Model Description/Application Slot Z Card
(MOT Digits) Slot Z Inputs Slot E Card (MOT Digits) Slot E Inputs
787-4X 4 Winding/Terminal Current Differential 6 ACI
(81, 82, 85)
IAW1, IBW1, ICW1,
IAW2, IBW2, ICW2
6ACI
(A1, A2, A5)
IAW3, IBW3, ICW3,
IAW4, IBW4, ICW4
787-3E 3 Winding/Terminal Current Differential
1 Neutral Current Input
3 Voltage Inputs (Phase)
6ACI
(81, 82, 85)
IAW1, IBW1, ICW1,
IAW2, IBW2, ICW2
4ACI/3AVI
(72, 73, 76, 77)
IAW3, IBW3, ICW3,
IN, VA, VB, VC
787-3S 3 Winding/Terminal Current Differential
3 Voltage Inputs (Phase)
1 Voltage Input (Vsync or Vbat)
6ACI
(81, 82, 85)
IAW1, IBW1, ICW1,
IAW2, IBW2, ICW2
3ACI/4AVI
(71, 75)
IAW3, IBW3, ICW3,
VS/VBAT, VA, VB,
VC
SEL-787-3, -4 Transformer Protection
Relay

SEL-787-3, -4 Data Sheet Schweitzer Engineering Laboratories, Inc.
2
Table 2 Protection Element Table
Protection Elements
4 Windings
3 Windings With IN
Channel and 3-Phase
Voltages
3 Windings With
VS/VBAT Channel and
3-Phase Voltages
SEL-787-4X SEL-787-3E SEL-787-3S
87 Phase Differential X X X
REF Restricted Earth Fault XaXaXa
50P Phase Overcurrent X X X
50Q Neg.-Seq. Overcurrent XXX
50G Ground Overcurrent X X X
50N Neutral Overcurrent X
51P Phase Time-Overcurrent X X X
51Q Neg.-Seq. Time-Overcurrent XXX
51G Ground Time-Overcurrent X X X
51PC Combined Winding Phase Time-
Overcurrent XXX
51GC Combined Winding Ground Time-
Overcurrent XXX
51N Neutral Time-Overcurrent X
27P Phase Undervoltage X X
27PP Phase-to-Phase Undervoltage X X
27S VS Channel Undervoltage X
59P Phase Overvoltage X X
59PP Phase-to-Phase Overvoltage X X
59Q Neg.-Seq. Overvoltage X X
59G Ground Overvoltage X X
59S VS Channel Overvoltage X
24 Volts/Hz X X
25 Synchronism Check X
32 Directional Power X X
49RTD RTDs XXX
60LOP Loss of Potential X X
81 Over- and Underfrequency X X
BF Breaker Failure X X X
aRefer to Table 3 for the available REF elements based on the configuration of Winding 3.
Table 3 Available Differential and REF Elements Based on the Configuration of Winding 3
Elements SEL-787-3E SEL-787-3S SEL-787-4X
Differential Protection Windings (Standard) 3 3 4
REF Elements (Standard) 1 0 0
Differential Protection Windings
(Winding 3 Configured for REF)
223
REF Elements
(Winding 3 Configured for REF)
322

Schweitzer Engineering Laboratories, Inc. SEL-787-3, -4 Data Sheet
3
➤Standard Protection Features. Make use of standard dual-slope differential protection with harmonic blocking and
restraint for as many as four windings and as many as three independent restricted earth fault (REF) elements for
sensitive ground-fault detection in grounded wye-transformers. The SEL-787 Transformer Protection Relay allows
configuration of Winding 3 for either differential or REF protection. Refer to Table 3 for the available REF elements
based on the configuration of Winding 3. The relay also includes phase, negative-sequence, residual ground, and
neutral-ground overcurrent elements for backup protection. Breaker failure protection for as many as four three-pole
breakers also comes standard.
➤Additional Protection Features. Take advantage of SEL-787-3E/S volts/hertz protection with frequency tracking
from 15 to 70 Hz for generator step-up and variable frequency applications. Use over- and underfrequency and over-
and undervoltage elements to implement load shedding and other control schemes on the relay.
➤Synchronism Check/Station DC Battery Monitor. Program the VS/VBAT voltage channel in the SEL-787-3S
model to perform a synchronism check across a circuit breaker or to monitor dc voltage levels of the substation
battery.
➤Transformer Monitoring. Measure accumulated through-fault levels with the transformer through-fault monitor.
Additionally, use the optional 4–20 mA or RTD thermal inputs to monitor ambient, load tap-changer (LTC) tank,
and transformer oil temperature.
➤Operator Controls. Take advantage of eight programmable front-panel pushbuttons, each with two programmable
tricolor LEDs, for various uses, such as easy trip and close control and status indication for all the breakers. Use the
operator control interface pushbuttons to easily implement local and remote operator control schemes using 32 local
and 32 remote control bits. Use SELOGIC®control equations and slide-in, configurable front-panel labels to change
the function and identification of target LEDs and operator control pushbuttons and LEDs.
➤Relay and Logic Settings Software. Use ACSELERATOR QuickSet®SEL-5030 Software to reduce engineering costs
related to relay settings and logic programming and to simplify development of SELOGIC control equations. Verify
proper CT polarity and phasing through use of the built-in phasor display.
➤Metering and Reporting. Use built-in metering functions that eliminate separately mounted metering devices.
Analyze Sequential Events Recorder (SER) reports and oscillographic event reports for rapid commissioning,
testing, and post-fault diagnostics. Unsolicited SER protocol allows station-wide collection of binary SER messages.
➤Additional Standard Features. Further enhance your power system protection by taking advantage of several other
SEL-787 standard features in communication, monitoring, and support. Modbus®RTU, Event Messenger support,
MIRRORED BITS®communications, as well as load profile and breaker wear monitoring all come standard with the
SEL-787. The relay also supports 12 additional external RTDs (SEL-2600 series module), IRIG-B input, advanced
SELOGIC control equations, IEEE®C.37.118-compliant synchrophasor protocol, and an SEL-2812 compatible ST®
fiber-optic serial port.
➤Optional Features. Communicate with a number of additional optional communications protocols and ports,
digital/analog I/O, and RTDs. Optional communications protocols include IEC 61850, Modbus®TCP/IP, Simple
Network Time Protocol (SNTP), DNP3 LAN/WAN, DNP3 serial, and IEC 60870-5-103. Elective communications
ports include EIA-232 or EIA-485, and single or dual, copper or fiber-optic Ethernet ports. Several digital/analog
I/O options are available. These include 4 AI/4 AO, 4 DI/4 DO, 8 DI, 8 DO, 3 DI/4 DO/1 AO, and 4 DI/3 DO. An
optional 10 internal RTD card is also available for the SEL-787 relay.
➤Language Support. Choose English or Spanish for your serial ports, including the front-panel serial port. The
standard relay front-panel overlay is in English; a Spanish overlay is available as an ordering option.

SEL-787-3, -4 Data Sheet Schweitzer Engineering Laboratories, Inc.
4
Functional Overview
Figure 1 SEL-787-3E Functional Diagram
3
3
3
1
Temperature Alarm
and Trip
SEL-787-3E Transformer Protection Relay
52
52
Overcurrent Time-Overcurrent
Combined
Time-
Overcurrent
Overcurrent Time-Overcurrent
• Sequential Events Recorder
• Event Reports
• SEL ASCII, Ethernet*, Modbus TCP*, IEC 61850*, DNP3
LAN/WAN*, DNP3 Serial*, 60870-5-103*, Modbus RTU,
Telnet, FTP, SNTP*, and DeviceNet
TM
Communications*
• Synchrophasor Data and IEEE C37.118 Compliant Protocol
• Front-Panel Programmable Tricolor LED Targets
• Two Inputs and Three Outputs Standard
• I/O Expansion*--Additional Contact Inputs, Contact
Outputs, Analog Inputs, Analog Outputs, and RTD Inputs
• Single or Dual Ethernet Copper or Fiber-Optic
Communications Port*
Σ5151 P
G
8787
Overcurrent Time-Overcurrent
Overcurrent Time-Overcurrent
3232
2424 8181 O
U
Volts/Hertz Frequency
LOPLOP
27P27P 5959
Restricted Earth
Fault (REF)
Directional
Power
Loss of Potential
Undervoltage Overvoltage
Current
Differential
3
52
• Battery-Backed Clock, IRIG-B Time Synchronization
• Instantaneous, Differential, Harmonic, and RMS
Metering
• Programmable Pushbuttons and LED Indicators
• Through-Fault Monitoring
• Transformer Thermal Monitoring
• Circuit Breaker Contact Wear Monitor
• Advanced SELOGIC Control Equations
• 32 Programmable Display Messages
• MIRRORED BITS Communications
*Optional Functions
Internal or External
RTD Input

Schweitzer Engineering Laboratories, Inc. SEL-787-3, -4 Data Sheet
5
Figure 2 SEL-787-3S Functional Diagram
3
3
3
1
Temperature Alarm
and Trip
SEL-787-3S Transformer Protection Relay
52
52
Overcurrent Time-Overcurrent
Combined
Time-
Overcurrent
Overcurrent Time-Overcurrent
• Sequential Events Recorder
• Event Reports
• SEL ASCII, Ethernet*, Modbus TCP*, IEC 61850*, DNP3
LAN/WAN*, DNP3 Serial*, 60870-5-103*, Modbus RTU,
Telnet, FTP, SNTP*, and DeviceNet
TM
Communications*
• Synchrophasor Data and IEEE C37.118 Compliant Protocol
• Front-Panel Programmable Tricolor LED Targets
• Two Inputs and Three Outputs Standard
• I/O Expansion*--Additional Contact Inputs, Contact
Outputs, Analog Inputs, Analog Outputs, and RTD Inputs
• Single or Dual Ethernet Copper or Fiber-Optic
Communications Port*
Σ5151 P
G
8787
Overcurrent Time-Overcurrent
Undervoltage Overvoltage
3232
2424 8181 O
U
Volts/Hertz Frequency
LOPLOP
27P27P 5959
Synch Check
Directional
Power
Loss of Potential
Undervoltage Overvoltage
Current
Differential
3
52
• Battery-Backed Clock, IRIG-B Time Synchronization
• Instantaneous, Differential, Harmonic, and RMS
Metering
• Programmable Pushbuttons and LED Indicators
• Through-Fault Monitoring
• Transformer Thermal Monitoring
• Circuit Breaker Contact Wear Monitor
• Advanced SELOGIC Control Equations
• 32 Programmable Display Messages
• MIRRORED BITS Communications
*Optional Functions
Internal or External
RTD Input
2525
27S27S 59S59S

SEL-787-3, -4 Data Sheet Schweitzer Engineering Laboratories, Inc.
6
Figure 3 SEL-787-4X Functional Diagram
3
Temperature Alarm
and Trip
SEL-787-4X Transformer Protection Relay
52
52
Overcurrent Time-Overcurrent
Combined
Time-
Overcurrent
Overcurrent Time-Overcurrent
• Sequential Events Recorder
• Event Reports
• SEL ASCII, Ethernet*, Modbus TCP*, IEC 61850*, DNP3
LAN/WAN*, DNP3 Serial*, 60870-5-103*, Modbus RTU,
Telnet, FTP, SNTP*, and DeviceNet
TM
Communications*
• Synchrophasor Data and IEEE C37.118 Compliant Protocol
• Front-Panel Programmable Tricolor LED Targets
• Two Inputs and Three Outputs Standard
• I/O Expansion*--Additional Contact Inputs, Contact
Outputs, Analog Inputs, Analog Outputs, and RTD Inputs
• Single or Dual Ethernet Copper or Fiber-Optic
Communications Port*
Σ51
51
P
G
87
87
Current
Differential
3
• Battery-Backed Clock, IRIG-B Time Synchronization
• Instantaneous, Differential, Harmonic, and RMS
Metering
• Programmable Pushbuttons and LED Indicators
• Through-Fault Monitoring
• Transformer Thermal Monitoring
• Circuit Breaker Contact Wear Monitor
• Advanced SELOGIC Control Equations
• 32 Programmable Display Messages
• MIRRORED BITS Communications
*Optional Functions
Internal or External
RTD Input
3
52
52
Overcurrent Time-Overcurrent
Combined
Time-
Overcurrent
Overcurrent Time-Overcurrent
Σ51
51
P
G
3

Schweitzer Engineering Laboratories, Inc. SEL-787-3, -4 Data Sheet
7
Protection Features
The SEL-787 Relay offers dual-slope differential charac-
teristic for transformer differential protection. The
SEL-787 includes a complete set of phase, negative-
sequence, and residual overcurrent elements for each ter-
minal (winding), as well as REF and neutral-overcurrent
elements for grounded wye transformers.
Use as many as 12 independent RTD-driven thermal
elements with trip and alarm levels to monitor ambient
and equipment temperatures throughout the substation.
For the optional volts/hertz element, you can add three-
phase voltage inputs that give the SEL-787 volts/hertz
protection with definite-time and time-delay
characteristics, along with directional power, over- and
underfrequency, and over- and undervoltage elements with
two independent pickup levels and time delay.
Transformer Differential
The SEL-787 has three restrained differential elements
(87R). These elements use operate and restraint quanti-
ties calculated from as many as four winding input cur-
rents. Set the differential elements with either single- or
dual-slope percentage differential characteristics.
Figure 4 illustrates a dual-slope setting. The percent-
slope characteristic helps prevent undesired relay opera-
tion because of a possible unbalance between CTs during
external faults. CT unbalance can result from TAP
changing in the power transformer and error difference
between the CTs on either side of a power transformer.
Figure 4 Dual-Slope Restrained Differential
Characteristic
With the SEL-787, you can choose harmonic blocking,
harmonic restraint, or both, to provide reliable
differential protection during transformer inrush
conditions. Even-numbered harmonics (second and
fourth) provide security during energization, while fifth-
harmonic blocking provides security for overexcitation
conditions. Set second-, fourth-, and fifth-harmonic
thresholds independently.
An additional alarm function for the fifth-harmonic
current employs a separate threshold and an adjustable
timer to warn of overexcitation. This may be useful for
transformer applications in or near generating stations. A
set of unrestrained differential current elements simply
compares the differential operating current quantity to a
setting value, typically about 10 times the TAP setting.
This pickup setting is only exceeded for internal faults.
The three independent unrestrained differential elements
(87U) provide rapid assertion without delay when
differential operate current levels exceed the 87U pickup
threshold that is set. Typical 87U pickup level settings
are between 8 and 10 per unit of operate current.
Restricted Earth Fault (REF)
Protection
Apply the REF protection feature to provide sensitive
detection of internal ground faults on grounded
wye-connected transformer windings and auto-
transformers. Order the SEL-787-3E with the Slot Ecard
containing the 1 A or 5 A neutral current input for REF
protection. The single-phase 1 A or 5 A CT, provided as
a Slot Eordering option, is used for introduction of neu-
tral operating current. Also, across all available models,
you can program Winding 3 for inclusion in differential
protection or program Phase A and/or Phase B of
Winding 3 for REF protection.
When Winding 3 is set for REF protection, you can
apply the operate quantity (neutral current) to Phase A or
Phase B of Winding 3 for REF protection. Polarizing
current is derived from the residual current calculated for
the protected winding(s). A sensitive directional element
determines whether the fault is internal or external. Zero-
sequence current thresholds supervise tripping.
Overcurrent Protection
The SEL-787 offers instantaneous overcurrent and time-
overcurrent elements. All the elements can be controlled
individually by means of SELOGIC torque control equa-
tions associated with the element.
Instantaneous Overcurrent Elements
The following instantaneous overcurrent elements are
available in the SEL-787.
➤Four instantaneous phase overcurrent (50P) elements
per winding that operate on the maximum of the
phase currents. A peak detection algorithm is used to
enhance element sensitivity during high-fault current
conditions where severe CT saturation may occur.
➤Per-phase instantaneous overcurrent (50P) elements,
one element per phase, that operate on the corre-
sponding phase current of Winding 3 (only available
Operating Region
Restraining Region
IRT
70%
25%
IOP
087P = 0.3
Slope 2
(SLP2)
IRS1 = 6
Slope 1
(SLP1)

SEL-787-3, -4 Data Sheet Schweitzer Engineering Laboratories, Inc.
8
on Winding 3). A peak detection algorithm is used to
enhance element sensitivity during high-fault current
conditions where severe CT saturation may occur.
➤Two instantaneous negative-sequence overcurrent
(50Q) elements per winding that operate on the calcu-
lated negative-sequence current.
➤Two residual instantaneous overcurrent (50G) ele-
ments per winding that operate on the calculated
residual (3I0) current.
➤Two neutral instantaneous overcurrent (50N) ele-
ments that operate on the neutral current associated
with the neutral channel (MOT dependent).
Time-Overcurrent Elements
The time-overcurrent elements support the IEC and U.S.
(IEEE) time-overcurrent characteristics shown in
Table 4. Electromechanical disk reset capabilities are
provided for all time-overcurrent elements. The follow-
ing time-overcurrent elements are available in the
SEL-787.
➤One maximum phase time-overcurrent (51P) element
per winding that operates on the maximum of the cor-
responding winding phase currents.
➤Three per-phase (A-, B-, and C-phase) time-overcur-
rent (51P) elements, one element per phase, that oper-
ate on the corresponding phase current of Winding 3
(only available on Winding 3).
➤One negative-sequence time-overcurrent (51Q) ele-
ment per winding that operates on the calculated neg-
ative-sequence current.
➤One residual time-overcurrent (51G) element per
winding that operates on the calculated residual (3I0)
current.
➤One neutral time-overcurrent (51N) element that
operates on the neutral current associated with the
neutral channel (MOT dependent).
Combined Time-Overcurrent Elements
The combined time-overcurrent elements can be used for
transformers connected to ring-bus or breaker and one-
half systems. The relay only allows you to combine
Winding 1 and Winding 2 and/or Winding 3 and
Winding 4 currents. The combined time-overcurrent ele-
ments support the IEC and U.S. (IEEE) time-overcurrent
characteristics shown in Table 4. Electromechanical disk
reset capabilities are provided for all combined time-
overcurrent elements. The following combined time-
overcurrent elements are available in SEL-787.
➤Two phase time-overcurrent (51P) elements, one each
for combined Windings 1 and 2 and Windings 3
and 4, that operate on the maximum of the corre-
sponding combined phase currents.
➤Two zero-sequence time-overcurrent (51G) elements,
one each for combined Windings 1 and 2 and
Windings 3 and 4, that operate on the calculated zero-
sequence current of the corresponding combined cur-
rents.
Breaker Failure Protection
The SEL-787 offers breaker failure protection for as
many as four three-pole breakers. Use breaker failure
detection to issue re-trip commands to the failed breaker
or to trip adjacent breakers using the relays contact out-
put logic or communications-based tripping schemes.
Breaker failure is initiated by the breaker failure initiate
(BFI) SELOGIC input. The BFI input is typically driven
by local and remote open/trip commands to the breaker.
Once the BFI input is received, the breaker failure
element monitors positive- and negative-sequence
current magnitudes and the breaker auxiliary contacts to
determine when to initiate the breaker failure delay timer.
If current or breaker auxiliary contact status does not
indicate an open breaker condition within the time set by
the breaker failure delay timer, the element issues a
breaker failure trip output.
Figure 5 Breaker Failure Protection
Volts/Hertz Protection
Overexcitation occurs when the magnetic core of a
power apparatus becomes saturated. When saturation
occurs, stray flux is induced in nonlaminated compo-
nents, which can result in overheating. By ordering the
voltage option for the SEL-787, you can add a volts/hertz
element to detect overexcitation. An SEL-787 with
optional voltage inputs provides a sensitive definite-time
delayed element, plus a tripping element with a compos-
ite operating time.
For example, the relay calculates the present transformer
volts/hertz as a percentage of nominal, based on present
measured values and the nominal voltage and frequency
settings. The relay starts a timer when the system voltage
causes an excursion that exceeds the volts/hertz
overexcitation setting. If the condition remains for the set
time delay, the relay asserts and typically provides an
Table 4 Time-Overcurrent Curves
U.S. (IEEE) IEC
Moderately Inverse Standard Inverse
Inverse Very Inverse
Very Inverse Extremely Inverse
Extremely Inverse Long-Time Inverse
Short-Time Inverse Short-Time Inverse
BFD
0
BFT
BFI
|I1| + |I2|
0.02 • INOM
52A
52ABF

Schweitzer Engineering Laboratories, Inc. SEL-787-3, -4 Data Sheet
9
alarm function. The element is supervised by the
SELOGIC torque control equation, which enables or
disables the element as required by the application.
Use the SEL-5806 Volts/Hertz User Curve Design
Software to set the user-defined curve (see Figure 6). For
tripping, the relay provides a time-integrating element
with a settable operating characteristic. You can set the
relay element to operate as an inverse-time element; a
user-defined curve element; a composite element with an
inverse-time characteristic and a definite-time
characteristic; or a dual-level, definite-time element.
For any of these operating characteristics, the element
provides a linear reset characteristic with a settable reset
time. The torque control setting also supervises this
element. The tripping element has a percent-travel
operating characteristic similar to that used by an
induction-disk, time-overcurrent element. This
characteristic emulates the heating effect of
overexcitation on transformer components.
Figure 6 SEL-5806 Volts/Hertz User Curve Design
Example
Over- and Undervoltage Protection
The SEL-787 with voltage inputs contains phase over-
and undervoltage, and sequence overvoltage elements
that help create protection and control schemes, such as
undervoltage load shedding or standby generation
start/stop commands. All voltage elements provide two
pickup levels with definite-time delay settings. The fol-
lowing over- and undervoltage elements are available:
➤Phase undervoltage (27P) and overvoltage (59P) ele-
ments that operate on the measured phase-to-neutral
voltages.
➤Phase-to-phase undervoltage (27PP) and overvoltage
(59PP) elements that operate on the measured
phase-to-phase voltages.
➤Negative-sequence overvoltage (59Q) and residual-
ground overvoltage (59G) elements that operate on
the calculated negative-sequence and residual-ground
voltage, respectively.
➤Phase undervoltage (27S) and phase overvoltage
(59S) elements that operate on VS channel voltage.
Loss-of-Potential Detection
The SEL-787 with optional voltage inputs contains loss-
of-potential (LOP) detection logic on the three-phase
voltage input to the relay. The LOP logic detects open
voltage transformer fuses or other conditions that cause a
loss of relay secondary voltage input. The SEL-787 with
optional voltage inputs includes LOP logic that detects
one, two, or three potentially open fuses. This patented
LOP logic is unique, because it does not require settings
and is universally applicable. The LOP feature allows for
the blocking of protection elements to add security
during voltage transformer fuse failure.
Synchronism Check/Station DC
Battery Monitor
The SEL-787 with the voltage option allows you to pro-
gram the VS/Vbat voltage channel for use as either syn-
chronism check or station dc battery monitor. When
programmed as a synchronism-check channel, single-
phase voltage (phase-to-neutral or phase-to-phase) can
be connected to the voltage input for synchronism check
or hot/dead line check across the circuit breaker to which
the three-phase voltages are assigned. When the channel
is programmed for battery monitor, the station dc battery
voltage can be monitored. The relay also allows you to
program over- and undervoltage elements on the voltage
channel.
Over- and Underfrequency Protection
The SEL-787 with optional voltage inputs contains four
frequency elements. Each element operates as either an
over- or underfrequency element with or without time
delay, depending on the element pickup setting.
If the element pickup setting is less than the nominal
system frequency setting, the element operates as an
underfrequency element, picking up if the measured
frequency is less than the set point. If the pickup setting
exceeds the nominal system frequency, the element
operates as an overfrequency element, picking up if the
measured frequency exceeds the set point.
The SEL-787 with optional voltage inputs uses the
positive-sequence voltage to determine system
frequency. All frequency elements are disabled if the
positive-sequence voltage is less than the minimum
voltage threshold.

SEL-787-3, -4 Data Sheet Schweitzer Engineering Laboratories, Inc.
10
Directional Power Element
Protection
The SEL-787 with optional voltage inputs provides two
directional power elements for detecting real (WATTS)
or reactive (VARS) directional power flow levels for the
transformer winding(s) associated with the three-phase
voltage input. Each directional power element has a
definite-time delay setting.
RTD Thermal Protection
When the SEL-787 is equipped with either the optional
10 RTD input expansion card or an external SEL-2600
RTD module with as many as 12 RTD inputs, as many as
12 thermal elements in the relay can be programmed for
two levels of thermal protection per element. Each RTD
input provides an alarm and trip thermal pickup setting in
degrees C, provides open and shorted RTD detection,
and is compatible with the following three-wire RTD
types:
➤PT100 (100 platinum)
➤NI100 (100 nickel)
➤NI120 (120 nickel)
➤CU10 (10 copper)
Operator Controls
Operator controls eliminate traditional panel control
switches. Eight conveniently sized operator controls are
located on the relay front panel (see Figure 7 and
Figure 8). The SER can be set to track operator controls.
Use SELOGIC control equations to change operator
control functions. It is possible to use configurable labels
to change all text in Figure 7 and Figure 8.
Figure 7 Operator Controls (787-4X Model)
Figure 8 Operator Controls (787-3S/3E Models)
The following operator control descriptions are for
factory-set logic.
LOCK: The LOCK operator control blocks selected
functions. Press it for at least three seconds to enable or
disable the lock function. When the LOCK pushbutton is
enabled, the CLOSE operator control is blocked.
BRKRn (n = 1, 2, 3, or 4): Each of these
pushbuttons allows you to select the breaker on which a
CLOSE or TRIP control operation is to be performed.
Only one breaker can be selected at any given time.
Breaker select status for a given breaker is indicated by
the upper pushbutton LED. The lower pushbutton LED
indicates CLOSED/OPEN (RED/GREEN, respectively)
status of the corresponding breaker.
CLOSE and TRIP: Use the CLOSE and TRIP operator
controls to close and open the circuit breaker. You can
program these controls with intentional time delays to
support operational requirements for breaker-mounted
relays. This allows you to press the CLOSE or TRIP
pushbutton, then move to an alternate location before the
breaker command executes.
AUXn (n = 1, 2): The AUXn pushbutton is available
for you to program additional control for your specific
application.
BRKR4
SELECTED
CLOSED/OPEN
BRKR1
CLOSE
CLOSE
BREAKER OPEN
TRIP
AUX1
SELECTED
BRKR2
SELECTED
CLOSED/OPEN
BRKR3
SELECTED
CLOSED/OPEN
CLOSED/OPEN
ENABLED
LOCK
DISABLED
ENABLED
LOCK
DISABLED
SELECTED
CLOSED/OPEN
BRKR1
BRKR2
SELECTED
CLOSED/OPEN
BRKR3
SELECTED
CLOSED/OPEN
CLOSE
CLOSE
BREAKER OPEN
TRIP
AUX1
AUX2

Schweitzer Engineering Laboratories, Inc. SEL-787-3, -4 Data Sheet
11
SEL-787 Application
The SEL-787 is designed to provide differential and
overcurrent protection for power transformers, generator
step-up transformers, and autotransformers with as many
as four windings/terminals. In addition, the SEL-787
contains advanced integration and control features that
will allow its application in a wide variety of automation
and control schemes. Refer to Section 2: Installation and
Section 4: Protection and Logic Functions of the instruc-
tion manual for more details.
Figure 9 shows the application of an SEL-787-4X Relay
for protection of a three-winding transformer. You can
configure windings 1, 2, and 4 on the relay for
differential protection, and you can apply the 50/51
elements associated with each winding towards
overcurrent protection. You can configure A-phase and
B-phase of Winding 3 on the relay for REF protection for
windings 1 and 2, respectively. You can configure
C-phase of Winding 3, along with the RTD thermal
elements, to provide fan bank control and protection. Use
additional RTD thermal elements to monitor load tap
changer (LTC) tank temperatures and SELOGIC
programming to indicate temperature differential alarms
between transformer and LTC tank temperatures.
Figure 10 shows an SEL-787-3E Relay protecting an
autotransformer with three terminals. You can configure
windings 1, 2, and 3 on the relay for differential
protection, and you can apply the 50/51 elements
associated with each winding towards overcurrent
protection. You can configure Channel IN on the relay
for REF protection. You can use the three-phase voltage
inputs for V/Hz, over- and undervoltage, over- and
underfrequency, and directional power protection.
Apply the transformer through-fault monitoring of the
SEL-787 to keep track of accumulated through-fault I2t
values. Monitor the number of through faults,
accumulated I2t, and fault duration times to determine
the frequency (through-fault events per day, week,
month, or year) and impact of external faults on the
transformer.

SEL-787-3, -4 Data Sheet Schweitzer Engineering Laboratories, Inc.
12
Figure 9 SEL-787-4X Provides 3-Winding Transformer Differential Protection, REF Protection, Overcurrent
Protection, and Fan Bank Control With LTC Monitoring
SEL-787-4X Relay
52-4
52-1
A2 (H1)
B2 (H2)
C2 (H3)
a (T1)
b (T2)
c (T3)
Fiber Port
SEL-2600
N
L
E01
E03
E04
E06
E08
E05
E07
E09
E10
E12
E02
A2 B2 C2
Z01
Z02
Z03
Z04
Z05
Z06
52-2 Z07
Z08
Z09
Z10
Z11
Z12
IAW3
IBW3
ICW3
IAW4
IBW4
ICW4
IAW1
IBW1
ICW1
IAW2
IBW2
ICW2
RTDs
E11
Ambient
Temp
Top Oil
Temp
LTC
Note: The CT secondary circuit should be grounded in the relay cabinet.
2000/5 A
13.8 kV
30 MVA
69 kV
200/5 A
IBW3
IAW3
A1 B1 C1
400/5 A
a b c
A1 (X1)
B1 (X2)
C1 (X3)
138 kV
T3
T2
T1
X3
X2
X1
H3
H2
H1

Schweitzer Engineering Laboratories, Inc. SEL-787-3, -4 Data Sheet
13
Figure 10 SEL-787-3E Provides Auto-Transformer Differential Protection, REF Protection, Overcurrent Protection,
and Voltage-Based Protection
52-1
abc
52-3
ABC
SEL-787-3E Relay
IAW3
IBW3
ICW3
IN
IBW2
ICW2
Delta
Tertiary
E01
E02
E03
E04
E05
E06
E07
E08
Z09
Z10
Z11
Z12
52-2
abc
Z01
Z02
Z03
Z04
Z05
Z06
IAW1
IBW1
ICW1
Z08
Z07 IAW2
A (H1)
B (H2)
C (H3)
a (X1) c (X3)
b (X2)
Note: The CT secondary circuit should be grounded in the relay cabinet.
E12
E10
E09
E11
VN
VC
VB
VA
150/5 A
230 kV
50 MVA
138 kV
250/5 A
138 kV
250/5 A
H3H2H1
X3X2X1

SEL-787-3, -4 Data Sheet Schweitzer Engineering Laboratories, Inc.
14
Relay and Logic Settings Software
ACSELERATOR QuickSet simplifies settings and provides
analysis support for the SEL-787. There are several ways
to create and manage relay settings with ACSELERATOR
QuickSet.
➤Develop settings offline with an intelligent settings
editor that only allows valid settings.
➤Create SELOGIC control equations with a drag-and-
drop text editor.
➤Use online help to configure proper settings.
➤Organize settings with the relay database manager.
➤Use a simple PC communications link to load and
retrieve settings.
With ACSELERATOR QuickSet, you can verify settings
and analyze power system events with the integrated
waveform and harmonic analysis tools.
You can use the following features of ACSELERATOR
QuickSet to monitor, commission, and test the SEL-787.
➤Use the human-machine interface (HMI) to monitor
meter data, Relay Word bits, and output contacts sta-
tus during testing.
➤Use the PC interface to remotely retrieve power sys-
tem data.
➤Use the Event Report Analysis tool for easy retrieval
and visualization of ac waveforms and digital inputs
and outputs the relay processes.
➤Use the graphical current phasor displays in the HMI
for visualizing differential current relationships.
Metering and Monitoring
The SEL-787 provides extensive metering capabilities.
See Specifications for metering and power measurement
accuracies. As shown in Table 5, metered quantities
include phase voltages and currents; neutral current;
sequence voltages and currents; harmonics, power,
frequency, and energy; and maximum/minimum logging
of selected quantities.
Table 5 SEL-787 Metered Values (Model Dependent)
Quantity Description
IxWn(x= A, B, C, n= 1, 2, 3, 4) Winding phase current magnitude and angle, primary A
IN1 Neutral current magnitude and angle, primary A
IGWn(n= 1, 2, 3, 4) Residual-ground fault current and angle per winding, primary A
3I2Wn(n= 1, 2, 3, 4) Negative-sequence current and angle per winding, primary A
IOPz(z= 1, 2, 3) Differential operate current, scaled to TAP
IRTz(z= 1, 2, 3) Differential restraint current, scaled to TAP
InF2, InF4, InF5 (n= 1, 2, 3, 4) Current harmonics, InF2/IOPn(%) for 2nd, 4th, 5th harmonics
VA, VB, VC Phase voltages and angles, primary volts, for wye-connected potential transformers
VAB, VBC, VCA Phase-to-phase voltages and angles, primary volts, for delta-connected potential transformers
VG Residual-ground voltage and phase angle, primary volts, for wye-connected potential transformers
3V2 Negative-sequence voltage and phase angle, primary volts
kVA, kW, kVAR Calculated apparent, real, and reactive power scaled to primary values
MWh, MVARh Three-phase positive and negative megawatt-hours, megavar-hours
PF Power factor (leading or lagging)
VS Synchronism-check voltage channel, voltage magnitude and angle, primary volts
VDC Station battery voltage
FREQ Measured system frequency (Hz)
FREQS Measured frequency (Hz) of synchronism-check channel
V/Hz Calculated volts/hertz in percent, using highest measured voltage and frequency
RTDn(n= 1 to 12) RTD temperature measurement (degrees C)

Schweitzer Engineering Laboratories, Inc. SEL-787-3, -4 Data Sheet
15
Synchronized Phasor Measurement
Combine the SEL-787 with an SEL IRIG-B time source
to measure the system angle in real time with a timing
accuracy of ±10 µs. Measure instantaneous voltage and
current phase angles in real time to improve system
operation with synchrophasor information. Replace state
measurement, study validation, or track system stability.
Use SEL-5077 SYNCHROWAVE®Server Software or
SEL-5078-2 SYNCHROWAVE®Console Software to view
system angles at multiple locations for precise system
analysis and system-state measurement (see Figure 11).
Figure 11 View of System Angle at Multiple Locations
Circuit Breaker Contact Wear
Monitor
Circuit breakers experience mechanical and electrical
wear every time they operate. Intelligent scheduling of
breaker maintenance takes into account the manufac-
turer’s published data of contact wear versus interruption
levels and operation count. With the breaker manufac-
turer’s maintenance curve as input data, the SEL-787
breaker monitor feature compares these input data to the
measured (unfiltered) ac current at the time of trip and
the number of close-to-open operations.
Every time the breaker trips, it integrates the measured
current information. When the result of this integration
exceeds the breaker wear curve threshold (see
Figure 12), the relay alarms via output contact,
communications port, or front-panel display. This kind of
information allows timely and economical scheduling of
breaker maintenance.
Figure 12 Breaker Contact Wear Curve and Settings
Through-Fault Monitoring
A through fault is an overcurrent event external to the
differential protection zone. While a through fault is not
an in-zone event, the currents required to feed this exter-
nal fault can cause great stress on the apparatus inside the
differential protection zone. Through-fault currents can
cause transformer winding displacement, leading to
mechanical damage and increased transformer thermal
wear. An SEL-787 through-fault event monitor gathers
current level, duration, and date/time for each through
fault. The monitor also calculates a simple I2t and cumu-
latively stores these data per phase. Use through-fault
event data to schedule proactive transformer bank main-
tenance and help justify through-fault mitigation efforts.
Apply the accumulated alarm capability of the relay to
indicate excess through-fault current (I2t) over time.
Event Reporting and Sequential
Events Recorder (SER)
Event reports and the SER simplify post-fault analysis
and improve understanding of simple and complex pro-
tective scheme operations. In response to a user-selected
trigger, the voltage, current, frequency, and element sta-
tus information contained in each event report confirms
the relay scheme and system performance for every fault.
Decide how much detail is necessary when you request
an event report (e.g., 1/4-cycle or 1/32-cycle resolution,
filtered or raw analog data, respectively).
The relay stores the most recent nineteen 64-cycle or
seventy-seven 15-cycle event reports in nonvolatile
memory. The relay always appends relay settings to the
bottom of each event report.
The following analog data formats are available:
➤1/4-cycle or 1/32-cycle resolution
➤Unfiltered or filtered analog
➤ASCII or Compressed ASCII
The relay SER feature stores the latest 1024 entries. Use
this feature to gain a broad perspective at a glance. An
SER entry helps to monitor input/output change-of-state
occurrences and element pickup/dropout.
The IRIG-B time-code input synchronizes the SEL-787
time to within ±5 ms of the time-source input.
A convenient source for this time code is an SEL-2401
Satellite-Synchronized Clock or the SEL-3530 Real
Time Automation Controller (RTAC), SEL-2032,
SEL-2030, or SEL-2020 Communications Processor (via
Serial Port 3 on the SEL-787).
San Antonio, TX
60.0 Hz
Chicago, IL
60.015 Hz
Monterrey, Mexico
59.996 Hz 59.996 Hz
Pullman, WA Philadelphia, PA
Tampa, FL
60.003 Hz
60.007 Hz
Pullman
Chicago
Philadelphia
Tam pa
San Antonio
Monterrey
kA Interrupted
(Set Point 1)
(Set Point 2)
(Set Point 3)
Breaker Manufacturer's
Maintenance Curve
Close to Open Operations

SEL-787-3, -4 Data Sheet Schweitzer Engineering Laboratories, Inc.
16
Available reports, which also show the status of digital
inputs and outputs, include the following:
➤Analog event reports that use filtered data and show
all analog channels at four samples per cycle.
➤Digital event reports that show pickup of protection
elements including overcurrent, demand, voltage
overexcitation, frequency, and over- and undervolt-
age elements at four samples per cycle.
➤Differential event reports that show differential
quantities, element pickup, SELOGIC control equa-
tion set variables, and inputs and outputs at four sam-
ples per cycle.
➤Raw analog event reports that use unfiltered data at
32 samples per cycle.
Automation
Flexible Control Logic and Integration Features
The SEL-787 is equipped with as many as four inde-
pendently operated serial ports: one EIA-232 port on the
front, one EIA-232 or EIA-485 port on the rear, one
fiber-optic port, and one EIA-232 or EIA-485 port option
card. The relay does not require special communications
software. Use any system that emulates a standard termi-
nal system for engineering access to the relay. Establish
local or remote communication by connecting
computers; modems; protocol converters; printers; an
SEL-3530 RTAC, SEL-2032, SEL-2030, or SEL-2020
Communications Processor; SCADA serial port; or an
RTU. Refer to Table 6 for a list of communications pro-
tocols available in the SEL-787. Apply an SEL commu-
nications processor as the hub of a star network, with
point-to-point fiber or copper connection between the
hub and the SEL-787.
Table 6 Communications Protocols (Sheet 1 of 2)
Type Description
Simple ASCII Plain language commands for human and simple machine communications.
Use for metering, setting, self-test status, event reporting, and other functions.
Compressed ASCII Comma-delimited ASCII data reports.
Allows external devices to obtain relay data in an appropriate format for direct import into spreadsheets and
database programs.
Data are checksum protected.
Extended Fast Meter and
Fast Operate
Binary protocol for machine-to-machine communications.
Quickly updates SEL-3530 RTAC, SEL-2032, SEL-2030, and SEL-2020 communications processors,
RTUs, and other substation devices with metering information, relay elements, I/O status, time tags, open
and close commands, and summary event reports.
Data are checksum protected.
Binary and ASCII protocols operate simultaneously over the same communications lines, so control
operator metering information is not lost while a technician is transferring an event report.
Direct communications with the SEL-2600 RTD Module are possible using the unsolicited Fast Meter
protocol to read incoming temperature data from the SEL-2600.
Fast SER Protocol Provides SER events to an automated data collection system.
DNP3 Serial or Ethernet-based DNP3 protocols.
Provides default and mappable DNP3 objects that include access to metering data, protection elements,
Relay Word bits, contact I/O, targets, SER, relay summary event reports, and setting group selection.
Modbus Serial- or Ethernet-based Modbus protocol with point remapping.
Includes access to metering data, protection elements, contact I/O, targets, SER, relay summary event
reports, and setting groups.
IEC 61850 Ethernet-based international standard for interoperability between intelligent devices in a substation.
Operates remote bits and I/O.
Monitors Relay Word bits and analog quantities.
Synchrophasors IEEE C37.118-compliant synchrophasors for system state, response, and control capabilities.
Event Messenger The use of the SEL-3010 allows you to receive alerts directly on your cell phone.
Alerts can be triggered through relay events and can include measured quantities by the relay.
DeviceNet Allows for connection to a DeviceNet network for access to metering data, protection elements, contact I/O,
targets, and setting groups.

Schweitzer Engineering Laboratories, Inc. SEL-787-3, -4 Data Sheet
17
SEL-787 control logic improves integration in the
following ways:
➤Replaces traditional panel control switches. Elimi-
nate traditional panel control switches with 32 local
bits. Set, clear, or pulse local bits with the front-panel
pushbuttons and display. Program the local bits into
the control scheme with SELOGIC control equations.
Use the local bits to perform functions such as a trip
test or a breaker trip/close.
➤Eliminates RTU-to-relay wiring. Eliminate RTU-to-
relay wiring with 32 remote bits. Set, clear, or pulse
remote bits using serial port commands. Program the
remote bits into the control scheme with SELOGIC
control equations. Use remote bits for SCADA-type
control operations such as trip, close, and settings
group selection.
➤Replaces traditional latching relays. Replace up to
32 traditional latching relays for such functions as
“remote control enable” with latch bits. Program
latch set and latch reset conditions with SELOGIC
control equations. Set or reset the nonvolatile latch
bits using optoisolated inputs, remote bits, local bits,
or any programmable logic condition. The latch bits
retain their state when the relay loses power.
➤Replaces traditional indicating panel lights.
Replace traditional indicating panel lights with 32
programmable displays. Define custom messages
(e.g., Breaker Open, Breaker Closed) to report
power system or relay conditions on the front-panel
display. Use advanced SELOGIC control equations to
control which messages the relay displays.
➤Eliminates external timers. Eliminate external tim-
ers for custom protection or control schemes with 32
general purpose SELOGIC control equation timers.
Each timer has independent time-delay pickup and
dropout settings. Program each timer input with the
element you want (e.g., time qualify a current ele-
ment). Assign the timer output to trip logic, transfer
trip communications, or other control scheme logic.
➤Eliminates settings changes. Selectable setting
groups make the SEL-787 ideal for applications
requiring frequent setting changes and for adapting
the protection to changing system conditions. The
relay stores four setting groups. Select the active
setting group by optoisolated input, command, or
other programmable conditions. Use these setting
groups to cover a wide range of protection and con-
trol contingencies. Switching setting groups switches
logic and relay element settings. Program groups for
different operating conditions, such as rental/spare
transformer applications, station maintenance, sea-
sonal operations, emergency contingencies, loading,
source changes, and downstream relay setting
changes.
Fast SER Protocol
SEL Fast Sequential Events Recorder (SER) protocol
provides SER events to an automated data collection
system. SEL Fast SER protocol is available on any rear
serial port. Devices with embedded processing capability
can use these messages to enable and accept unsolicited
binary SER messages from SEL-787 relays. SEL relays
and communications processors have two separate data
streams that share the same serial port. The normal serial
interface consists of ASCII character commands and
reports that are intelligible to people using a terminal or
terminal emulation package. The binary data streams can
interrupt the ASCII data stream to obtain information,
and then allow the ASCII data stream to continue. This
mechanism allows a single communications channel to
be used for ASCII communications (e.g., transmission of
a long event report) interleaved with short bursts of
binary data to support fast acquisition of metering or
SER data.
SNTP Ethernet-based protocol that provides time synchronization of the relay.
IEC 60870-5-103 Serial communications protocol–international standard for interoperability between intelligent devices in a
substation.
Table 6 Communications Protocols (Sheet 2 of 2)
Type Description

SEL-787-3, -4 Data Sheet Schweitzer Engineering Laboratories, Inc.
18
Ethernet Network Architectures
Figure 13 Simple Ethernet Network Configuration
Figure 14 Simple Ethernet Network Configuration With Dual Redundant Connections (Failover Mode)
Figure 15 Simple Ethernet Network Configuration With Ring Structure (Switched Mode)
CAT 5 shielded twisted pair (STP)
cables with RJ-45 connectors
(SEL-C627/C628) for
copper Ethernet ports
OR
Fiber-optic Ethernet cables with
LC connectors (SEL-C808) for
fiber-optic Ethernet ports
Set Port 1 (Ethernet) settin
g
s in each relay.
NETWORK
SEL-787
SEL-787
SEL-787
SEL-787
NETWORK
Set Port 1 (Ethernet) settin
g
s in each relay.
CAT 5 shielded twisted pair (STP) cables with RJ-45
connectors (SEL-C627/C628) for copper Ethernet ports
OR
Fiber-optic Ethernet cables with LC connectors
(SEL-C808) for fiber-optic Ethernet ports
Set Port 1 (Ethernet) settings in each relay.
SEL-787SEL-787
NETWORK
CAT 5 shielded twisted pair (STP) cables
with RJ-45 connectors (SEL-C627/C628)
for copper Ethernet ports
OR
Fiber-optic Ethernet cables with
LC connectors (SEL-C808) for
fiber-optic Ethernet ports

Schweitzer Engineering Laboratories, Inc. SEL-787-3, -4 Data Sheet
19
Additional Features
MIRRORED BITS Relay-to-Relay
Communications
The SEL-patented MIRRORED BITS®communications
technology provides bidirectional relay-to-relay digital
communication. MIRRORED BITS communications can
operate independently on as many as two EIA-232 rear
serial ports and one fiber-optic rear serial port on a single
SEL-787.
This bidirectional digital communication creates eight
additional virtual outputs (transmitted MIRRORED BITS)
and eight additional virtual inputs (received MIRRORED
BITS) for each serial port operating in the MIRRORED
BITS mode (see Figure 16). Use these MIRRORED BITS to
transmit/receive information between upstream relays
and a downstream relay to enhance coordination and
achieve faster tripping for downstream faults. MIRRORED
BITS technology also helps reduce total scheme
operating time by eliminating the need to assert output
contacts to transmit information.
Figure 16 MIRRORED BITS Transmit and Receive Bits
Status and Trip Target LEDs
The SEL-787 includes 24 tricolor status and trip target
LEDs on the front panel. When shipped from the factory,
all LEDs are predefined and fixed in settings. You can
reprogram these LEDs for specific applications. This
combination of targets is explained and shown in
Figure 18. Some front-panel relabeling of LEDs may be
needed if you reprogram them for unique or specific
applications—see Configurable Labels.
Event Messenger Points
The SEL-787, when used with the SEL-3010 Event
Messenger, can allow for ASCII-to-voice translation of
as many as 32 user-defined messages, along with analog
data that has been measured or calculated by the relay.
This combination allows you to receive voice message
alerts (on any phone) regarding Relay Word bit transi-
tions in the relay.
Verbal notification of breaker openings, fuse failures,
RTD alarms, etc. can now be sent directly to your cell
phone through the use of your SEL-787 and SEL-3010
(must be connected to an analog telephone line). In
addition, messages can include an analog value such as
current, voltage, or power measurements made by the
SEL-787.
Configurable Labels
Use the configurable labels to relabel the operator con-
trols and LEDs (shown in Figure 18) to suit the installa-
tion requirements. This feature includes preprinted labels
(with factory-default text), blank label media, and a Mic-
rosoft®Word template on CD-ROM. This allows quick,
professional-looking labels for the SEL-787. Labels may
also be customized without the use of a PC by writing the
new label on the blank stock provided. The ability to cus-
tomize the control and indication features allows specific
utility or industry procedures to be implemented without
the need for adhesive labels.
Additional Ordering Options
The following options can be ordered for the SEL-787
model (see the SEL-787-3,-4 Model Option Table for
details).
➤Single or dual port Ethernet 10/100BASE-T or
100BASE-FX, Modbus TCP, SNTP, DNP3 Serial,
DNP3 LAN/WAN, FTP, Telnet, IEC 61850,
IEC 60870-5-103
➤EIA-232 or EIA-485 communications
➤Additional EIA-232 or EIA-485 port
➤Analog I/O (4 AI/4 AO)
➤Digital I/O (4 DI/4 DO, 8 DI, 8 DO, 3 DI/4 DO/1 AO,
4 DI/3 DO)
➤Voltage input for synchronism check/station DC bat-
tery monitor
➤10 RTDs
➤Conformal coating for chemically harsh and high-
moisture environments
➤The relay supports the Spanish language as an order-
ing option.
SEL-787
Transmit
Receive
Transmit
Receive
.
.
.
.
Relay 2
0
0
0
1
0
0
.
.
.
.
1
0
0
0
0
0
TMB1
TMB2
TMB8
RMB1
RMB2
RMB8 RMB8
TMB1
TMB2
TMB8
.
.
.
.
.
.
RMB1
RMB2
.
.

SEL-787-3, -4 Data Sheet Schweitzer Engineering Laboratories, Inc.
20
Wiring Diagram for SEL-787-3E Model Option
Figure 17 Wiring Diagram SEL-787-3E Transformer Protection Relay
RX
TX
5 4 3 2 1
9 8 7 6
5 4 3 2 1
9 8 7 6
Port 4 DeviceNet
(Optional)
V–
CAN_L
SHIELD
CAN_H
V+
A
C
B
Typical Wiring
Prot.
Alarm
OUT101
OUT102
OUT103
A01 A02 A03 A04 A05 A06 A07 A08 A09 A10 A11 A12 C01 C02 C03 C04
IRIG-B
-/N+/H
IAW1 IBW1 ICW1 IAW2
TX+
TX–
RX+
RX–
SHIELD
(Optional)
Port 4A EIA-485
IRIG-B Time Source
≤ 1000 m
FO Cable**
1–12 RTDs
Front
Port 3
86T
Optional Input/Output Cards
+
—
+
—
+
—
+
—
+
—
+
—
+
—
+
—
+
—
+
—
10 RTDs
4 Digital Inputs / 4 Digital Outputs
3 Digital Inputs / 4 Digital Outputs / 1 Analog Output
4 Analog Inputs / 4 Analog Outputs
8 Digital Inputs
8 Digital Outputs
(+)
(–)
86T
IN101 IN102
CONTROL INPUTSINPUT POWER OUTPUT CONTACTS
SEL-787-3E
Transformer Protection Relay
** SEL Fiber-Optic Cables
240-1506 — 1 m (3.3 ft) ST/ST
240-1507 — 5 m (16.4 ft) ST/ST
240-1508 — 15 m (49.2 ft) ST/ST
Other lengths available by request
Power Supply
110–240 Vac
24–48 Vdc
110–250 Vdc
(Optional
485)
SEL 2812 compatible ST
Fiber-Optic Serial Port
(Optional)
52-3
OUT301
OUT302
OUTPUT CONTACTS
(Optional)
TC
TC
IBW2 ICW2
(+) (+)(–) (–)
86T
86T
Optional Ethernet (single or dual)
OR
PHASE AND NEUTRAL CURRENTS AND VOLTAGE INPUTS CURRENT INPUTS
Open Delta PT
VC N
52-1
a
(–)(+) (+)
SEL-2600 Series
External RTD Module
With ST Option
(Optional)
E01 E02 E03 E04 E11 E12 Z01 Z04 Z06 Z07Z05Z02 Z03 Z08 Z09 Z10 Z11 Z12
E10E09E08E07E06E05
ICW3 IN VA VB
52-2
a
b
c
a
b
c
XFMR 52-1
52-2
a
52-1
a
52-2
a
A diagram for a four-wire wye
connection is also available in
the instruction manual
4 Digital Inputs / 3 Digital Outputs
IAW3 IBW3