Schweitzer Engineering Laboratories SEL-421-7 User manual

Schweitzer Engineering Laboratories, Inc. SEL-421-7 Data Sheet
Protection, Automation, and Control
System With Sampled Values
or TiDL Technology
Key Features and Benefits
The SEL-421-7 Protection, Automation, and Control System With Sampled Values or TiDL Technology combines high-
speed distance and directional protection with complete control for a two-breaker bay.
➤Complete Distance Protection. You can apply as many as five zones of phase and ground distance and directional
overcurrent elements. Select mho or quadrilateral characteristics for any phase or ground distance element. Use the
optional high-speed distance elements and series-compensation logic to optimize protection for critical lines or
series-compensated lines. Patented coupling capacitor voltage transformer (CCVT) transient overreach logic
enhances the security of Zone 1 distance elements. Best Choice Ground Directional Element®logic optimizes
directional element performance and eliminates the need for many directional settings. Apply the distance and
directional elements in communications-based protection schemes such as POTT, DCB, and DCUB, or for
instantaneous or time-step backup protection.
➤Power Swing Blocking and Out-of-Step Tripping. You can select power swing blocking of distance elements for
stable power swings or out-of-step tripping for unstable power swings. Zero-setting, out-of-step detection logic is
available, eliminating the need for settings and power system studies.
➤Switch-Onto-Fault. Disconnect status inputs and voltage elements can enable high-speed protection.
➤Synchronism Check. Synchronism check can prevent circuit breakers from closing if the corresponding phases
across the open circuit breaker are excessively out of phase, magnitude, or frequency. The synchronism-check
function has a user-selectable synchronizing voltage source and incorporates slip frequency, two levels of maximum
angle difference, and breaker close time into the closing decision.
➤Reclosing Control. You can incorporate programmable single-pole or three-pole trip and reclose of one or two
breakers into an integrated substation control system. Synchronism and voltage checks from multiple sources
provide complete bay control.
➤Fault Locator. Utilities can efficiently dispatch line crews to quickly isolate line problems and restore service faster.
SEL-421-7 Protection,
Automation, and Control System

SEL-421-7 Data Sheet Schweitzer Engineering Laboratories, Inc.
2
➤Dual CT Input. You can combine currents within the relay from two sets of CTs for protection functions or keep
them separately available for monitoring and station integration applications.
➤Primary Potential Redundancy. Multiple voltage inputs to the relay provide primary voltage input redundancy.
Upon loss-of-potential (LOP) detection, the relay can use inputs from an electrically equivalent source connected
to the relay. Protection remains in service without compromising security.
➤Comprehensive Metering. The built-in, high-accuracy metering functions can improve feeder loading. Use watt
and VAR measurements to optimize feeder operation. Minimize equipment needs with full metering capabilities,
including: rms, maximum/minimum, demand/peak, energy, and instantaneous values.
➤Auxiliary Trip/Close Pushbuttons. These optional pushbuttons are electrically isolated from the rest of the relay.
They function independently from the relay and do not need relay power.
➤Bay Control. The relay provides bay control functionality with status indication and control for disconnect
switches. The relay features control for as many as two breakers and status indication of as many as three breakers.
Numerous predefined user-selectable mimic displays are available; the selected mimic appears on the front-panel
screen in one-line diagram format. The one-line diagram includes user-configurable labels for disconnect
switches, breakers, bay name, and display for as many as six analog quantities. The relay features SELOGIC
programmable local control supervision of breaker and disconnect switch operations.
➤Breaker Failure. High-speed (less than one cycle) open-pole detection logic reduces coordination times for critical
breaker failure applications. Apply the relay to supply breaker failure protection for all supported breakers. Logic
for breaker failure retrip and initiation of transfer tripping is included.
➤IEC 60255-149 Compliant Thermal Model. The relay can provide a configurable thermal model for the protection
of a wide variety of devices. This function can activate a control action or issue an alarm or trip when equipment
overheats as a result of adverse operation conditions. A separate resistance temperature detector (RTD) module is
required for this application.
➤Ethernet Access. The optional Ethernet card grants access to all relay functions. Use IEC 61850 Manufacturing
Message Specification (MMS) or DNP3 protocol directly to interconnect with automation systems. You can also
connect to DNP3 networks through a communications processor. Use File Transfer Protocol (FTP) for high-speed data
collection. Connect to substation or corporate LANs to transmit synchrophasors by using TCP or UDP internet protocols.
➤Serial Data Communication. The relay can communicate serial data through SEL ASCII, SEL Fast Message,
SEL Fast Operate, MIRRORED BITS®, and DNP3 protocols. Synchrophasor data are provided in either SEL Fast
Message or IEEE C37.118 format.
➤Automation. The enhanced automation features include programmable elements for local control, remote control,
protection latching, and automation latching. Local metering on the large front-panel LCD eliminates the need for
separate panel meters. Serial and Ethernet links efficiently transmit key information, including metering data, protection
element and control I/O status, synchrophasor data, IEC 61850 Edition 2 GOOSE messages, Sequential Events
Recorder (SER) reports, breaker monitoring, relay summary event reports, and time synchronization. Apply expanded
SELOGIC®control equations with math and comparison functions in control applications. Incorporate as many as
1000 lines of automation logic to accelerate and improve control actions.
➤Synchrophasors. You can make informed load dispatch decisions based on actual real-time phasor measurements
from relays across your power system. Record streaming synchrophasor data from the relay for system-wide disturbance
recording. Control the power system by using local and remote synchrophasor data.
➤Breaker and Battery Monitoring. You can schedule breaker maintenance when accumulated breaker duty
(independently monitored for each pole) indicates possible excess contact wear. The relay records electrical and
mechanical operating times for both the last operation and the average of operations since function reset. Alarm
contacts provide notification of substation battery voltage problems (as many as two independent battery monitors
in some SEL-400 series relays) even if voltage is low only during trip or close operations.
➤Digital Secondary Systems (DSS) Technologies. You can order the relay as either an SV subscriber relay or a
TiDL relay. DSS capable relays receive current and voltage information that is published by remote merging units
instead of standard PT and CT inputs. DSS technologies reduce copper cable lengths and associated installation
labor costs and improve the overall safety of the substation.
➤IEC 61850-9-2LE SV Relay. The SV subscriber relay can subscribe to current and voltage information that is
published by as many as seven remote SV merging units that are compliant with the IEC 61850-9-2LE guideline.
➤TiDL Relay. The TiDL relay can receive current and voltage information from as many as eight SEL-TMUs (TiDL
Merging Units) over direct point-to-point fiber-optic connections. The TiDL relay automatically synchronizes data
collection, alleviating the need or impact of an external clock on protection.

Schweitzer Engineering Laboratories, Inc. SEL-421-7 Data Sheet
3
➤Selective Protection Disabling. The subscriber or TiDL relay provides selective disabling of protection functions
by using hard-coded logic or available torque-control equations in case of a loss of communications between your
merging unit and relay that results in the loss of relevant analog data.
➤Current Summation. The relay can combine multiple SV stream currents to simplify external wiring.
➤Six Independent Settings Groups. The relay includes group logic to adjust settings for different operating conditions,
such as station maintenance, seasonal operations, emergency contingencies, loading, source changes, and adjacent
relay settings changes. Select the active group settings by control input, command, or other programmable conditions.
➤Software-Invertible Polarities. Inverting individual or grouped CT and PT polarities allows you to account for
field wiring or zones of protection changes. CEV files and all metering and protection logic use the inverted polarities,
whereas COMTRADE event reports do not use inverted polarities but rather record signals as applied to the relay.
➤Parallel Redundancy Protocol (PRP). PRP provides seamless recovery from any single Ethernet network failure.
The Ethernet network and all traffic are fully duplicated with both copies operating in parallel.
➤IEC 61850 Operating Modes. The relay supports IEC 61850 standard operating modes such as Test, Blocked,
On, and Off.
➤IEEE 1588, Precision Time Protocol (PTP). PTP provides high-accuracy timing over an Ethernet network.
➤Digital Relay-to-Relay Communications. MIRRORED BITS communications can monitor internal element conditions
between bays within a station, or between stations, using SEL fiber-optic transceivers. Send digital, analog, and
virtual terminal data over the same MIRRORED BITS channel.
➤Sequential Events Recorder (SER). The SER records the last 1000 events, including setting changes, startups,
and selectable logic elements.
➤Oscillography and Event Reporting. The relay records voltages, currents, and internal logic points at a sampling
rate as fast as 8 kHz. Offline phasor and harmonic-analysis features allow investigation of bay and system performance.
Time-tag binary COMTRADE event reports with high-accuracy time stamping for accuracy better than 10 s.
➤Digitally Signed Upgrades. The relay supports upgrading the relay firmware with a digitally signed upgrade file.
The digitally signed portion of the upgrade file helps ensure firmware and device authenticity after it is sent over a
serial or Ethernet connection.
➤Increased Security. The relay divides control and settings into seven relay access levels; the relay has separate
breaker, protection, automation, and output access levels, among others. Set unique passwords for each access level.
➤Rules-Based Settings Editor. You can communicate with and set the relay by using an ASCII terminal or use
Grid Configurator to configure the relay and analyze fault records with relay element response. Use as many as
200 aliases to rename any digital or analog quantity in the relay.

SEL-421-7 Data Sheet Schweitzer Engineering Laboratories, Inc.
4
Functional Overview
Figure 1 SEL-421-7 SV Subscriber or TiDL Functional Overview
ENV
50BF 5150
50BF 5150
79
4
EIA-232
1
IRIG-B
2
Ethernet
DSS
Inputs
Station Bus
Process Bus
21 67 68
81O
U
SEL-421-7
27 59
32
Mapped BK1
Currents
Mapped 52A1
Statuses
Mapped 52A2
Statuses
Mapped
Voltages
Mapped BK2
Currents
Four-port Ethernet card ordering option depicted.
ANSI NUMBERS/ACRONYMS AND FUNCTIONS
21 Phase and Ground Distance
25 Synchronism Check
27 Undervoltage
32 Directional Power
49 IEC 60255-Compliant Thermal Model
50 Overcurrent
(Phase, Zero-Sequence, and Negative-Sequence)
50BF Dual Breaker Failure Overcurrent
51 Time-Overcurrent
(Phase, Zero-Sequence, and Negative-Sequence)
59 Overvoltage
67 Directional Overcurrent
(Phase, Zero-Sequence, and Negative-Sequence)
68 Out-of-Step Block/Trip
79 Single- and Three-Pole Reclosing
81 Over- and Underfrequency
ADDITIONAL FUNCTIONS
16 SEC Access Security (Serial, Ethernet)
85 RIO SEL MIRRORED BITS Communications
BRM Breaker Wear Monitor
DFR Event Reports
ENV SEL-2600 RTD Module*
LGC SELOGIC Control Equations
LOC Fault Locator
MET High-Accuracy Metering
PMU Synchrophasors
SBM Station Battery Monitor
SER Sequential Events Recorder
SIP Software-Invertible Polarities
* Optional Feature
Note: Both copper and fiber-optic Ethernet ports are available.
16 S
E
C
LGCDFRBRM MET
PMU SERSBM SIP
49
25

Schweitzer Engineering Laboratories, Inc. SEL-421-7 Data Sheet
5
SV
The SEL-421-7 SV Subscriber subscribes to data streams
that are published from a merging unit, such as the
SEL-421-7 SV Publisher or SEL-401 Protection, Auto-
mation, and Control Merging Unit. The SEL-421-7 SV
Publisher provides full backup protection while the
SEL-401 can provide basic phase overcurrent and
breaker failure protection in the absence of communica-
tion. Using the process bus, the SEL-421-7 SV Publisher
or SEL-401 can provide voltage and current information
to multiple relays that subscribe to SV streams (see
Figure 1 and Figure 2). The data are synchronized using
Precision Time Protocol (PTP).
TiDL
The SEL-421-7 TiDL receives and automatically syn-
chronizes data streams from connected and commissioned
SEL-TMUs. The TiDL technology does not require an
external time source for local relay protection functions.
Figure 2 SEL-421-7 SV Publisher Functional Overview
Five-port Ethernet card ordering option depicted.
Bus
3
Line
Bus
3
21
1
1
25
50BF
5150
50BF
5150
67 68
79
81
O
U
SEL-421-7
27 59
ENV
4
EIA-232
2
Ethernet
Station Bus
(Ports 5C, 5D)
1
IRIG-B
2
Ethernet
Process Bus
(Ports 5A, 5B)
32
1
Ethernet
Enginnering
Access
(Port 5E)
ANSI NUMBERS/ACRONYMS AND FUNCTIONS
21 Phase and Ground Distance
25 Synchronism Check
27 Undervoltage
32 Directional Power
49 IEC 60255-Compliant Thermal Model
50 Overcurrent
(Phase, Zero-Sequence, and Negative-Sequence)
50BF Dual Breaker Failure Overcurrent
51 Time-Overcurrent
(Phase, Zero-Sequence, and Negative-Sequence)
59 Overvoltage
67 Directional Overcurrent
(Phase, Zero-Sequence, and Negative-Sequence)
68 Out-of-Step Block/Trip
79 Single- and Three-Pole Reclosing
81 Over- and Underfrequency
ADDITIONAL FUNCTIONS
16 SEC Access Security (Serial, Ethernet)
85 RIO SEL MIRRORED BITS Communications
BRM Breaker Wear Monitor
DFR Event Reports
ENV SEL-2600 RTD Module*
LGC SELOGIC Control Equations
LOC Fault Locator
MET High-Accuracy Metering
PMU Synchrophasors
SBM Station Battery Monitor
SER Sequential Events Recorder
SIP Software-Invertible Polarities
* Optional Feature
Note: Both copper and fiber-optic Ethernet ports are available.
LGCDFRBRM MET
PMU SERSBM SIP
16
S
E
C
3
49
Figure 3 SV Network
Process Bus
q
qTime synchronization
is required for SV
communications. Time
synchronization can be
done over a process
bus or station bus
Figure 4 SEL TiDL System
T-Protocol

SEL-421-7 Data Sheet Schweitzer Engineering Laboratories, Inc.
6
Protection Features
Complete Distance Protection
The SEL-421-7 simultaneously measures as many as five
zones of phase and ground mho distance protection plus
five zones of phase and ground quadrilateral distance
protection. You can apply these distance elements,
together with optional high-speed distance elements, in
communications-assisted and step-distance protection
schemes. You can use expanded SELOGIC control equa-
tions to tailor the relay further to your particular application.
The relay includes LOP detection, load encroachment,
and CCVT transient detection logic for enhanced security.
Optional series-compensated line logic can also be added
to prevent overreach of the Zone 1 distance element,
resulting from the series capacitor transient response.
Each of the distance elements has a specific reach setting.
The ground distance elements include three zero-sequence
compensation factor settings (k01, k0R, and k0F) to cal-
culate ground fault impedance accurately. Setting k01
uses positive-sequence quantities to adjust zero-sequence
transmission line impedance for accurate measurement.
Settings k0F and k0R account for forward and reverse
zero-sequence mutual coupling between parallel trans-
mission lines.
Figure 5–Figure 8 show the performance times of the
high-speed and standard distance elements for a range of
faults, locations, and source impedance ratios (SIR).
Subcycle Tripping Times Using Optional High-Speed Elements
Figure 5 Mho Single-Phase-to-Ground Faults
Figure 6 Mho Phase-to-Phase Faults
Fault Location as % of Reach Setting
0% 20% 40% 60% 80% 100%
Time in Cycles
Standard Speed Mho Ground Elements
0.25
0.50
0.75
1.25
1.50
1.0
1.75
0
SIR = 0.1
SIR = 1.0
SIR = 10.0
Fault Location as % of Reach Setting
0% 20% 40% 60% 80% 100%
Time in Cycles
High-Speed Mho Ground Elements
0.25
0.50
0.75
1.25
1.50
1.0
1.75
0
SIR = 0.1
SIR = 1.0
SIR = 10.0
Fault Location as % of Reach Setting
0% 20% 40% 60% 80% 100%
Time in Cycles
Standard Speed Mho Phase Elements
0.25
0.50
0.75
1.25
1.50
1.0
1.75
0
SIR = 0.1
SIR = 1.0
SIR = 10.0
Fault Location as % of Reach Setting
0% 20% 40% 60% 80% 100%
Time in Cycles
High-Speed Mho Phase Elements
0.25
0.50
0.75
1.25
1.50
1.0
1.75
0
SIR = 0.1
SIR = 1.0
SIR = 10.0

Schweitzer Engineering Laboratories, Inc. SEL-421-7 Data Sheet
7
Mho Distance Elements
The SEL-421-7 uses mho characteristics for phase and
ground distance protection. Two zones are fixed in the
forward direction, and the remaining three zones can be
set for either forward or reverse. All mho elements use
positive-sequence memory polarization that expands the
operating characteristic in proportion to the source imped-
ance (Figure 9). This provides dependable, secure opera-
tion for close-in faults.
As an optional addition to the standard distance elements,
there are three zones (either three forward, or two forward
and one reverse) of high-speed distance elements. These
high-speed elements use voltage and current phasors derived
from a fast half-cycle filter to provide subcycle tripping
times. Settings are automatically associated with the stan-
dard element zone reach, requiring no additional settings.
Quadrilateral Distance Elements
The SEL-421-7 provides five zones of quadrilateral
phase and ground distance characteristics for improved
fault and arc resistance coverage and reach-limiting action
on short lines. The top line of the quadrilateral character-
istic automatically tilts with load flow to avoid under-
and overreaching. Available settings prevent overreach-
ing of the quadrilateral characteristic from nonhomoge-
neous fault current components. You can use the mho and
quadrilateral distance elements separately or concur-
rently.
Out-of-Step Detection
The relay provides two different algorithms for out-of-step
detection. One of the two schemes may be selected by
the user.
The zero-setting method requires no power system stud-
ies or any settings (other than enabling). Using local voltage
measurements (see Figure 10) to closely approximate the
swing center voltage (SCV) allows the relay to use the rate-
of-change of SCV to quantify the power swing condition.
The second algorithm is a conventional out-of-step detec-
tion that provides timers and blinders that are set outside
any of the distance element reach settings. A power swing
is declared when an impedance locus travels through the
blinders slower than a preset time.
Figure 7 Quadrilateral Single-Phase-to-Ground Faults
Figure 8 Quadrilateral Phase-to-Phase Faults
Fault Location as % of Reach Setting
0% 20% 40% 60% 80% 100%
Time in Cycles
Standard Speed Quad Ground Elements
0.25
0.50
0.75
1.25
1.50
1.0
1.75
0
SIR = 0.1
SIR = 1.0
SIR = 10.0
Fault Location as % of Reach Setting
0% 20% 40% 60% 80% 100%
Time in Cycles
High-Speed Quad Ground Elements
0.25
0.50
0.75
1.25
1.50
1.0
1.75
0
SIR = 0.1
SIR = 1.0
SIR = 10.0
Fault Location as % of Reach Setting
0% 20% 40% 60% 80% 100%
Time in Cycles
Standard Speed Quad Phase Elements
0.25
0.50
0.75
1.25
1.50
1.0
1.75
0
SIR = 0.1
SIR = 1.0
SIR = 10.0
Fault Location as % of Reach Setting
0% 20% 40% 60% 80% 100%
Time in Cycles
High-Speed Quad Phase Elements
0.25
0.50
0.75
1.25
1.50
1.0
1.75
0
SIR = 0.1
SIR = 1.0
SIR = 10.0
Figure 9 Mho Characteristic
Expanded
Characteristic
Steady-State
Characteristic
Relay Reach
Z
R
Z
S
X
R

SEL-421-7 Data Sheet Schweitzer Engineering Laboratories, Inc.
8
Directional Elements
The SEL-421-7 includes a number of directional
elements for supervision of overcurrent elements and
distance elements. The negative-sequence directional
element uses the same patented principle proven in the
SEL-321. This directional element can be applied in vir-
tually any application, regardless of the amount of
negative-sequence voltage available at the relay location.
The following three directional elements working together
provide directional control for the ground overcurrent
elements:
➤Negative-sequence voltage-polarized directional
element
➤Zero-sequence voltage-polarized directional element
➤Zero-sequence current-polarized directional element
Our patented Best Choice Ground Directional Element
selects the best ground directional element for the system
conditions and simplifies directional element settings.
(You can override this automatic setting feature for spe-
cial applications.)
Communications-Assisted
Tripping Schemes
Use MIRRORED BITS communications with SEL fiber-
optic transceivers for 3–6 ms relay-to-relay transmission
time. Among the schemes supported are the following:
➤Permissive overreaching transfer tripping (POTT)
for two- or three-terminal lines
➤Directional comparison unblocking (DCUB) for
two- or three-terminal lines
➤Directional comparison blocking (DCB)
Use the SELOGIC control equation TRCOMM to program
specific elements, combinations of elements, inputs, etc.,
to perform communications scheme tripping and other
scheme functions. The logic readily accommodates the
following conditions:
➤Current reversals
➤Breaker open at one terminal
➤Weak-infeed conditions at one terminal
➤Switch-onto-fault conditions
Step-distance and time-overcurrent protection provide
reliable backup operation should the communications
channel be lost.
Combined Current for Protection
Flexibility
For traditional relays, when protecting a line fed from two
breakers, such as a breaker-and-a-half system or double-
breaker system, you must parallel the CTs before con-
necting these inputs to the relay. The relay accepts two
separate CT inputs (these CTs can be a different ratio) and
combines these currents mathematically. This allows col-
lecting separate current metering and breaker monitor infor-
mation for each breaker and breaker failure functions on a
per-breaker basis. Breaker diagnostic reports from the
SEL-421 provide you comparative breaker information
that you can use for advanced, proactive troubleshooting.
Multifunction Recloser
With Flexible Applications
The SEL-421-7 includes both single-pole and three-pole
trip and reclose functions, for either one or two breakers
(Figure 11). Synchronism check is included for breaker
control. Synchronizing and polarizing voltage inputs are
Figure 10 Applying VS to Approximate the Swing Center Voltage Provides an Accurate Local Quantity to Detect Power
Swings
θ
I
Vcosϕ
ϕ
SCV
Swing Center
SCV ≅VS • cos(ϕ)
O’ Z1R • I
Z1S • I Z
L1
I
V
R
E
R
V
S
E
S

Schweitzer Engineering Laboratories, Inc. SEL-421-7 Data Sheet
9
fully programmable with dead line/dead bus closing logic
as well as zero-closing-angle logic to minimize system
stress upon reclosing. Program as many as two single-
pole reclose attempts and four three-pole reclose attempts
as well as combined single-/three-pole reclosing sequences.
Select leader and follower breakers directly, or use a
SELOGIC control equation to determine reclosing order
based on system conditions. Coupled with independent-
pole-operating circuit breakers, this reclosing system
gives maximum flexibility for present system conditions
and for future requirements.
Additional Features
Front-Panel Display
The LCD shows event, metering, setting, and relay self-
test status information. The target LEDs display relay target
information as described in Figure 12.
The LCD is controlled by the navigation pushbuttons
(Figure 13), automatic messages the relay generates, and
user-programmed analog and digital display points. The
rotating display scrolls through alarm points, display points,
and metering screens. If none are active, the relay scrolls
through displays of the fundamental and rms metering
screens. Each display remains for a user-programmed
time (1–15 s) before the display continues scrolling. Any
message generated by the relay because of an alarm con-
dition takes precedence over the rotating display.
Figure 12 and Figure 13 show close-up views of the front
panel of the SEL-421. The front panel includes a 128 x 128
pixel, 3" x 3" LCD screen; LED target indicators; and
pushbuttons with indicating LEDs for local control func-
tions. The asserted and deasserted colors for the LEDs
are programmable. Configure any of the direct-acting
pushbuttons to navigate directly to any HMI menu item.
Quickly view events, alarm points, display points, or the
SER.
Figure 11 Two-Breaker Reclosing With Synchronism Check
52-1
52-2
Line
Bus 2
Bus 1
79
25
Figure 12 Factory-Default Status and Trip Target LEDs
(12 Pushbutton, 24 Target LED Option)
Figure 13 Factory-Default Front-Panel Display and
Pushbuttons
03/15/01 GROUP 1
00:00:05.387
EVENT: BCG T
LOCATION: 48.47
FREQ: 60.00
SHOT: 1P=0 3P=1
BK1 OPEN
BK2 CLOSED
EVENT SUMMARY 10002

SEL-421-7 Data Sheet Schweitzer Engineering Laboratories, Inc.
10
Bay Control
The SEL-421-7 provides dynamic bay one-line diagrams
on the front-panel screen with disconnect and breaker
control. You can download the Grid Configurator inter-
face from selinc.com to obtain additional user-selectable
bay types. The bay control can control as many as ten
disconnects and two breakers, depending on the one-line
diagram selected. Certain one-line diagrams provide sta-
tus for as many as three breakers and five disconnect
switches. Operate disconnects and breakers with ASCII
commands, SELOGIC control equations, Fast Operate
Messages, and from the one-line diagram. The one-line
diagram includes user-configurable apparatus labels and
as many as six user-definable analog quantities.
One-Line Bay Diagrams
The SEL-421-7 offers a variety of preconfigured one-line
diagrams for common bus configurations. Once you
select a one-line diagram, you can customize the names for
all of the breakers, disconnect switches, and buses. Most
one-line diagrams contain analog display points. You can
set these display points to any of the available analog quanti-
ties with labels, units, and scaling. The SEL-421-7
updates these values along with the breakers and switch
position in real time to give instant status and complete
control of a bay. The following diagrams demonstrate
some of the preconfigured bay arrangements available in
the SEL-421-7.
Programmable interlocks help prevent operators from
incorrectly opening or closing switches or breakers. The
SEL-421-7 not only prevents the operator from making
an incorrect control decision, but can notify and/or alarm
upon initiation of an incorrect operation.
Circuit Breaker Operations From the
Front Panel
Figure 14–Figure 17 are examples of some of the select-
able one-line diagrams in the SEL-421-7. Select the one-
line diagram from the Bay settings. Additional settings
for defining labels and analog quantities are also found in
the Bay settings. One-line diagrams are composed of the
following:
➤Bay names and bay labels
➤Busbar and busbar labels
➤Breaker and breaker labels
➤Disconnect switches and disconnect switch labels
➤Analog display points
Figure 18 shows the breaker control screens available
when the ENT pushbutton is pressed with the circuit
breaker highlighted as shown in Figure 18(a).
Figure 14 Breaker-and-a-Half
Figure 15 Ring Bus With Ground Switch
Figure 16 Double Bus/Double Breaker
Figure 17 Source Transfer Bus
BAYNAME
BK2
BK1
SW1 SW2
BK3
BAYLAB2BAYLAB1
BUSNAM1
BUSNAM2
ESCNAVIG
BAYNAME
6 ANALOGS
I:99999.9 A
V:99999.9 KV
P:99999.9 MW
Q:99999.9 MV
F:99.9 HZ
BAYLAB1
SW2
SW3
BK1
BK2
SW1
BAYLAB2
ESCNAVIG
BAYNAME
6 ANALOGS
I:99999.9 A
V:99999.9 KV
P:99999.9 MW
Q:99999.9 MV
F:99.9 HZ
BUSNAM1
SW2
SW3
BK1 BK2
SW1
BUSNAM2
ESCNAVIG
BAYNAME
BUSNAM1
BK1 BK2
BUSNAM2
BAYLAB1
I:99999.9 A
V:99999.9 KV
P:99999.9 MW
I:99999.9 A
V:99999.9 KV
P:99999.9 MW
ESCNAVIG

Schweitzer Engineering Laboratories, Inc. SEL-421-7 Data Sheet
11
Rack-Type Breakers Mosaics
The SEL-421-7 supports the display of rack-type (also
referred to as truck-type) circuit breakers. The rack-type
breakers have three positions: racked out, test, and racked
in. When in the test or racked-in positions, the breaker
can be displayed as open or closed. When racked out, no
breaker open/close display are available. The rack-type
breakers are a display-only functionality and do not impact
any circuit breaker control capabilities.
Status and Trip Target LEDs
The SEL-421-7 includes programmable status and trip
target LEDs, as well as programmable direct-action con-
trol pushbuttons on the front panel. Figure 12 and
Figure 13 show these targets.
The SEL-421-7 features a versatile front panel that you
can customize to fit your needs. 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. The blank
slide-in label set is included with the SEL-421-7. You
can use templates supplied with the relay or hand label
supplied blank labels and print label sets from a printer.
Alarm Points
You can display messages on the SEL-421-7 front-panel
LCD that indicate alarm conditions in the power system.
The relay uses alarm points to place these messages on
the LCD.
Figure 19 shows a sample alarm points screen. The relay
can display as many as 66 alarm points. The relay auto-
matically displays new alarm points while in manual-
scrolling mode and in autoscrolling mode. You can con-
figure the alarm points message and trigger it either
immediately by using inputs, communications, or condi-
tionally by using powerful SELOGIC control equations.
The asterisk next to the alarm point indicates an active
alarm. Use the front-panel navigation pushbuttons to
clear inactive alarms.
Figure 18 Screens for Circuit Breaker Selection
Bus Labels
BAYNAME
BAYNAME
OPEN BREAKER
CLOSE BREAKER
OPEN
Bkrnam
PRESS TO ACTIVATE
Bay not in
LOCAL Control!
Cannot issue
controls.
Press ENT with breaker highlighted
Breaker
Highlighted
(a) Bay Screen
(c) LOCAL bit NOT asserted
(b) Breaker Control Screen
After three seconds,
re-display the previous screen
BUS 2
Dis 4
Bkr 1
Dis 3
Dis 1 Dis 2
BUS 1
BUS T
Bay Name
Disconnect
Switch Label
Disconnect
Switch Label
Disconnect
Switch Label
Analog
Quantities
Display
Breaker
Label
6 ANALOGS
I:99999.9 A
V:99999.9 KV
P:99999.9 MW
Q:99999.9 MV
F:60.000 HZ
ESCNAVIG
ESCNAVIG

SEL-421-7 Data Sheet Schweitzer Engineering Laboratories, Inc.
12
Advanced Display Points
Create custom screens showing metering values, special
text messages, or a mix of analog and status information.
Figure 20 shows an example of how display points can
be used to show circuit breaker information and current
metering. As many as 96 display points can be created.
All display points occupy only one line on the display at
all times. The height of the line is programmable as either
single or double as shown in Figure 20. These screens
become part of the autoscrolling display when the front
panel times out.
Communications Features
See Specifications on page 23 for specific supported protocols.
The relay offers the following communications features:
➤Four independent EIA-232 serial ports.
➤Access to event history, relay status, and meter
information from the communications ports.
➤Password-controlled settings management and
automation features.
➤SCADA interface capability, including FTP,
IEC 61850, DNP3 LAN/WAN (via Ethernet), and
DNP3 (via serial port). The relay does not require
special communications software. You only need
ASCII terminals, printing terminals, or a computer
supplied with terminal emulation and a serial
communications port.
➤Synchrophasor data at 60 message-per-second data
format.
Ethernet Card
The Ethernet card has five small form-factor pluggable
(SFP) ports.aPORT 5A and PORT 5B are reserved for the
process bus network. PORT 5C and PORT 5D are reserved
for the station bus network. The process and station bus
networks support PRP and fast failover redundancy
modes. PORT 5E operates on an isolated network with a
unique IP address making it ideal for engineering and
data access. All ports support 100 Mbps speeds. PORT 5A
and PORT 5B also support 1 Gbps speeds to satisfy poten-
tially large traffic requirements on the process bus. The
process bus, station bus, and engineering access net-
Figure 19 Sample Alarm Points Screen
*Unauthorized Access
*Xfmr Fan Failed
*Xfmr Heat Overload
ALARM POINTS
Press to acknldge
Figure 20 Sample Display Points Screen
Circuit Breaker 1
--Closed--
DISPLAY POINTS
Circuit BK1 SF6 Gas
--Alarm--
Circuit Breaker 2
A PH= 119.6 A pri
SF6 ALARM
Figure 21 System Functional Overview
Automation or Synchrophasors
Over Ethernet:
Five Ethernet Ports
(PORT 5A, PORT 5B, PORT 5C,
PORT 5D, and PORT 5E)
100BASE-FX
1000BASE-X
C37.118
To Remote SEL Relay
Using M
IRRORED B ITS
Spare
Front Port Local
Operator or
Engineering Access
IEC 61850 or
DNP LAN/WAN
Communications
Processor
Serial Communication:
Three Rear EIA-232 Ports
One Front EIA-232 Port
aSFP transceivers are not included with the card and must be ordered
separately. See selinc.com/products/sfp for a list of compatible SFP
transceivers.

Schweitzer Engineering Laboratories, Inc. SEL-421-7 Data Sheet
13
works use separate MAC addresses and are logically
delineated, including in the Configured IED Description
(CID) file.b
Use popular Telnet applications for easy terminal com-
munications with SEL relays and other devices. Transfer
data at high speeds for fast file uploads. The Ethernet
card communicates using FTP applications for easy and
fast file transfers.
Communicate with SCADA by DNP3 and other substa-
tion IEDs by using IEC 61850 Manufacturing Message
Specification (MMS) and GOOSE messaging.
Choose Ethernet connection media options for primary
and standby connections:
➤10/100BASE-T twisted pair networkc
➤100BASE FX fiber-optic network
➤1000BASE-X fiber-optic networkd
Telnet and FTP
Use Telnet to access relay settings, metering, and event
reports remotely by using the ASCII interface. Use FTP to
transfer settings files to and from the relay via the high-
speed Ethernet port.
DNP3 LAN/WAN
DNP3 LAN/WAN provides the relay with DNP3 Level 2
Outstation functionality over Ethernet. Configure DNP3
data maps for use with specific DNP3 masters.
PTP
The Ethernet card provides the ability for the relay to accept
IEEE 1588 PTPv2 for data time synchronization. PTP
support includes the Default, Power System, and Power
Utility Automation Profiles. When connected directly to
a grandmaster clock providing PTP at 1-second synchro-
nization intervals, the relay can be synchronized to an
accuracy of ±100 ns in the PTP time scale.
SNTP Time Synchronization
Use SNTP to synchronize relays to as little as ±1 ms with
no time source delay. Use SNTP as a primary time source,
or as a backup to a higher accuracy time input to the relay.
PRP
Use PRP to provide seamless recovery from any single
Ethernet network failure, in accordance with IEC 62439-3.
The Ethernet network and all traffic are fully duplicated
with both copies operating in parallel.
HTTP Web Server
The relay can serve read-only webpages displaying cer-
tain settings, metering, and status reports. The web server
also allows quick and secure firmware upgrades over
Ethernet. As many as four users can access the embedded
HTTP server simultaneously.
IEC 61850 Ethernet Communications
IEC 61850 Ethernet-based communication protocols
provide interoperability between intelligent devices within
the substation. Standardized logical nodes allow inter-
connection of intelligent devices from different manufac-
turers for monitoring and control of the substation.
Eliminate system RTUs by streaming monitor and con-
trol information from the intelligent devices directly to
remote SCADA client devices.
bThis paragraph describes the five-port Ethernet card ordering option.
It does not apply to the four-port Ethernet card ordering option.
cFour-port Ethernet card ordering option only.
dGigabit speeds are only available on PORT 5A and PORT 5B of the five-
port Ethernet card ordering option.
Figure 22 Example PTP Network
GPS

SEL-421-7 Data Sheet Schweitzer Engineering Laboratories, Inc.
14
You can order the relay with IEC 61850 protocol for relay
monitor and control functions, including:
➤As many as 128 incoming GOOSE messages. You
can use the incoming GOOSE messages to control
as many as 256 control bits in the relay with <3 ms
latency from device to device depending on network
design. These messages provide binary control
inputs to the relay for high-speed control functions
and monitoring.
➤As many as eight outgoing GOOSE messages.
Configure outgoing GOOSE messages for Boolean
or analog data such as high-speed control and
monitoring of external breakers, switches, and other
devices. Boolean data are provided with <3 ms latency
from device to device depending on network design.
➤IEC 61850 Data Server. The relay equipped with
embedded IEC 61850 Ethernet protocol provides
data according to predefined logical node objects.
Each relay supports as many as seven unbuffered
MMS report client associations. Relevant Relay
Word bits are available within the logical node
data, so status of relay elements, inputs, outputs, or
SELOGIC control equations can be monitored.
➤As many as 256 virtual bits. Configure the virtual
bits within GOOSE messaging to represent a variety
of Boolean values available within the relay. These
bits that the relay receives are available for use in
SELOGIC control equations.
➤As many as 64 remote analog outputs. Assign the
remote analog outputs to virtually any analog quantity
available in the relay. You can also use SELOGIC
math variables to develop custom analog quantities
for assignment as remote analog outputs. Remote
analog outputs that use GOOSE messages provide
peer-to-peer transmission of analog data. Each relay
can receive as many as 256 remote analog inputs
and use those inputs as analog quantities within
SELOGIC control equations.
➤IEC 61850 standard operating modes. The relay
supports Test, Blocked, On, and Off. The relay also
supports Simulation mode for added flexibility.
MMS File Services
This service of IEC 61850 MMS provides support for file
transfers completely within an MMS session. All relay
files that can be transferred via FTP can also be transferred
via MMS file services.
MMS Authentication
When enabled via a setting in the Configured IED Descrip-
tion (CID) file, the relay requires authentication from any
client requesting to initiate an MMS session.
Architect Software
Use ACSELERATOR Architect SEL-5032 Software to
manage the IEC 61850 configuration for devices on the
network. This Windows-based software provides easy-
to-use displays for identifying and binding IEC 61850
network data among logical nodes that use IEC 61850-
compliant CID files. Architect uses CID files to describe
the data available in each relay.
Serial Communications
MIRRORED BITS Communications
The SEL patented MIRRORED BITS technology provides
bidirectional relay-to-relay digital communication.
Figure 23 shows two relays with SEL-2815 Fiber-Optic
Transceivers that use MIRRORED BITS communications.
MIRRORED BITS communications can operate simultane-
ously on any two serial ports. This bidirectional digital
communication creates additional outputs (transmitted
MIRRORED BITS) and additional inputs (received
MIRRORED BITS) for each serial port operating in the
MIRRORED BITS communications mode.
Communicated information can include digital, analog,
and virtual terminal data. Virtual terminal allows opera-
tor access to remote relays through the local relay. You
can use this MIRRORED BITS protocol to transfer infor-
mation between stations to enhance coordination and
achieve faster tripping.

Schweitzer Engineering Laboratories, Inc. SEL-421-7 Data Sheet
15
Open Communications Protocols
The relay does not require special communications software. ASCII terminals, printing terminals, or a computer sup-
plied with terminal emulation and a serial communications port are all that is required. Table 1 lists a brief description of
the terminal protocols.
Figure 23 Integral Communication Provides Secure Protection, Monitoring, and Control as Well as Terminal Access to
Both Relays Through One Connection
Fiber-Optic Cable
SEL-2815 SEL-2815
Bus 1 Bus 2
1Transmission Line 2
Digital, Analog, and Virtual Terminal Data
Other
Relays
Other
Relays
TX
RX
SEL-400 Series Relay
TX
RX
SEL-400 Series Relay
Table 1 Open Communications Protocol
Type Description
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 bay data in an appropriate format for
direct import into spreadsheets and database programs. Data are checksum protected.
Extended Fast Meter, Fast
Operate, and Fast SER
Binary protocol for machine-to-machine communications. Quickly updates communications processors, RTUs,
and other substation devices with metering information, bay element, 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 that control operator metering information is not lost
while a technician is transferring an event report.
Ymodem Support for reading event, settings, and oscillography files.
Optional DNP3 Level 2
Outstation
DNP with point remapping. Includes access to metering data, protection elements, contact I/O, targets, SER,
relay summary event reports, and settings groups.
IEEE C37.118 Phasor measurement protocol.
MIRRORED BITS SEL protocol for exchanging digital and analog information among SEL relays and for use as low-speed termi-
nal connection.
IEC 61850 Ethernet-based international standard for interoperability between intelligent devices in a substation.
PRP PRP provides redundant Ethernet network capabilities for seamless operation in the event of loss to one network.
SNTP Ethernet-based SNTP for time synchronization among relays.
FTP and Telnet Use Telnet to establish a terminal-to-relay connection over Ethernet. Use FTP to move files in and out of the
relay over Ethernet.

SEL-421-7 Data Sheet Schweitzer Engineering Laboratories, Inc.
16
Automation
Flexible Control Logic and
Integration Features
Use the control logic to perform the following:
➤Replace traditional panel control switches
➤Eliminate remote terminal unit (RTU)-to-bay wiring
➤Replace traditional latching relays
➤Replace traditional indicating panel lights
Eliminate traditional panel control switches with 64 local
control points. Set, clear, or pulse local control points
with the front-panel pushbuttons and display. Program
the local control points to implement your control scheme
via SELOGIC control equations. Use the local control
points for such functions as trip testing, enabling/disabling
reclosing, and tripping/closing circuit breakers.
Eliminate RTU-to-bay wiring with 64 remote control
points per relay. Set, clear, or pulse remote control points
via serial port commands. Incorporate the remote control
points into your control scheme via SELOGIC control
equations. Use remote control points for SCADA-type
control operations (e.g., trip, close, settings group selection).
Replace traditional latching relays for such functions as
remote control enable with 64 latching control points.
Program latch set and latch reset conditions with SELOGIC
control equations. Set or reset the latch control points via
control inputs, remote control points, local control points,
or any programmable logic condition. The relay retains
the states of the latch control points after turning on fol-
lowing a power interruption.
Replace traditional indicating panel lights and switches
with as many as 24 latching target LEDs and as many as
12 programmable pushbuttons with LEDs. Define cus-
tom messages (i.e., BREAKER OPEN, BREAKER CLOSED,
RECLOSER ENABLED) to report power system or relay con-
ditions on the large format LCD. Control displayed mes-
sages with SELOGIC control equations by driving the
LCD via any logic point in the relay.
SELOGIC Control Equations With
Expanded Capabilities and Aliases
Expanded SELOGIC control equations put relay logic in
the hands of the engineer. Assign inputs to suit your
application, logically combine selected bay elements for
various control functions, and assign outputs to your
logic functions.
Programming SELOGIC control equations consists of
combining relay elements, inputs, and outputs with
SELOGIC control equation operators (Table 2). Any ele-
ment in the Relay Word can be used in these equations.
For complex or unique applications, these expanded
SELOGIC functions allow superior flexibility.
Use the relay alias capability to assign more meaningful
names to analog and Boolean quantities. This improves
the readability of customized programming. Use as many
as 200 aliases to rename any digital or analog quantity.
The following is an example of possible applications of
SELOGIC control equations that use aliases.
Table 2 SELOGIC Control Equation Operators
Operator Type Operators Comments
Boolean AND, OR, NOT Allows combination of measuring units.
Edge Detection F_TRIG, R_TRIG Operates at the change of state of an internal function.
Comparison >, , =, <=, <, < >
Arithmetic +, –, *, / Uses traditional math functions for analog quantities in an easily programmable equation.
Numerical ABS, SIN, COS, LN, EXP,
SQRT, LOG
Precedence Control ( ) Allows multiple and nested sets of parentheses.
Comment #, (* *) Provides for easy documentation of control and protection logic.
=>>SET T <Enter>
1: PMV01,THETA
(assign the alias “THETA” to math variable PMV01)
2: PMV02,TAN
(assign the alias “TAN” to math variable PMV02)
=>>SET L <Enter>
1: # CALCULATE THE TANGENT OF THETA
2: TAN:=SIN(THETA)/COS(THETA)
(use the aliases in an equation)

Schweitzer Engineering Laboratories, Inc. SEL-421-7 Data Sheet
17
Add programmable control functions to your relay and
automation systems. New functions and capabilities enable
using analog values in conditional logic statements. The
following are examples of possible applications of
SELOGIC control equations with expanded capabilities.
➤Emulate a motor-driven reclose timer, including
stall, reset, and drive-to-lockout conditions.
➤Scale analog values for SCADA retrieval.
➤Initiate remedial action sequence based on load
flow before fault conditions.
➤Interlock breakers and disconnect switches.
➤Restrict breaker tripping in excessive duty
situations without additional relays.
➤Hold momentary change-of-state conditions for
SCADA polling.
Metering and Monitoring
Access a range of useful information in the relay with the
metering function. Metered quantities include fundamen-
tal primary and secondary current and voltage magni-
tudes and angles for each terminal. RMS voltage and
current metering is also provided. Fundamental phase
and real and reactive power, per-phase voltage magni-
tude, angle, and frequency are displayed in the metering
report for applications that use the relay voltage inputs.
Table 3 Metering Capabilities
Capabilities Description
Instantaneous Quantities
Voltages
VA, B, C (Y), VA, B, C (Z), V3V0, V1, 3V2
0–300 V with phase quantities for each of the six voltage sources available as separate
quantities.
Currents
IA, B, C (W), IA, B, C (X),
IAL, IBL, ICL, (combined currents),
IGL, I1L, 3I2L (combined currents)
Phase quantities for each of the two current sources available as separate quantities or
combined as line quantities.
Differential Metering
Currents
IA, B, C, I1, 3I2, 3I0
Local terminal/all
Remote Terminals
Differential Current
IA, B, C, I1, 3I2, 3I0
Local terminal/all
Remote terminals
Alpha Plane
k
alpha
Alpha plane ratio
Alpha plane angle
Power/Energy Metering Quantities
MW, MWh, MVAR, MVARh, MVA, PF, 
single-phase and three-phase
Available for each input set and as combined quantities for the line.
Demand/Peak Demand Metering
IA, B, C, 3I2, 3I0Thermal or rolling interval demand and peak demand.
MW, MVAR, MVA, single-phase Thermal or rolling interval demand and peak demand.
MW, MVAR, MVA, three-phase Thermal or rolling interval demand and peak demand.
Synchrophasors
Voltages (Primary Magnitude, Angle)
VA, B, C (Y), VA, B, C (Z)
Primary phase quantities (kV) for each of the six voltage sources available.
Currents
IA, B, C (W), IA, B, C (X)
Primary phase quantities (A) for each of the six voltage sources available.
Frequency
FREQ
dF/dT
Frequency (Hz) as measured by frequency source potential inputs.
Rate-of-change in frequency (Hz/s).

SEL-421-7 Data Sheet Schweitzer Engineering Laboratories, Inc.
18
Event Reporting and SER
Event reports and SER features simplify post-fault analy-
sis and help improve your understanding of both simple
and complex protective scheme operations. These fea-
tures also aid in testing and troubleshooting relay settings
and protective schemes.
Oscillography and Event Reporting
In response to a user-selected internal or external trigger,
the voltage, current, and element status information con-
tained in each event report confirms relay, scheme, and
system performance for every fault. The relay provides
sampling rates as fast as 8 kHz for analog quantities in a
COMTRADE file format, as well as eight-sample-per-
cycle and four-sample-per-cycle event reports. The relay
stores as much as 3 seconds of 8 kHz event data. The
relay supports inclusion of user-configurable analogs in
the events. Reports are stored in nonvolatile memory.
Relay settings operational in the relay at the time of the
event are appended to each event report.
Each relay provides event reports for analysis with soft-
ware such as SEL-5601-2 SYNCHROWAVE®Event Soft-
ware. With SYNCHROWAVEEvent, you can display
events from several relays to make the fault analysis eas-
ier and more meaningful. Because the different relays
time-stamp the events with values from their individual
clocks, be sure to time synchronize the relay with an
IRIG-B clock input or PTP source to use this feature.
Event Summary
Each time the relay generates a standard event report, it
also generates a corresponding event summary. This is a
concise description of an event that includes the follow-
ing information:
➤Relay/terminal identification
➤Event date and time
➤Event type
➤Event number
➤Time source
➤Active settings group
➤Targets asserted during the fault
➤Current magnitudes and angles for each terminal
➤Pre-fault and fault calculated zero- and negative-
sequence currents
➤Voltage magnitudes and angles
➤Terminals tripped for this fault
➤Recloser shot count at time of trigger (if applicable)
➤Fault location (if applicable)
➤Breaker status (open/close)
With an appropriate setting, the relay sends an event
summary in ASCII text automatically to one or more
serial ports each time an event report is triggered.
SV Reporting
The SV Subscriber includes a comprehensive report of
the SV communication stream. The ASCII command
COM SV displays statistics information from the sample
values stream to aid in troubleshooting.
SER
Use this feature to gain a broad perspective of relay ele-
ment operation. Items that trigger an SER entry are select-
able and can include as many as 250 monitoring points,
such as I/O change-of-state and element pickup/dropout.
The relay SER stores the latest 1000 events.
Analog Signal Profiling
The relay provides analog signal profiling for as many as
20 analog quantities. Select any analog quantity mea-
sured or calculated by the relay for analog signal profil-
ing. You can select signal sampling rates of 1, 5, 15, 30,
and 60 minutes through settings. The analog signal pro-
file report provides a comma-separated variable (CSV)
list that you can load into any spreadsheet or database for
analysis and graphical display.
SELOGIC enable/disable functions can start and stop sig-
nal profiling based on Boolean or analog comparison
conditions.
Substation Battery Monitor for DC
Quality Assurance
The relay measures and reports the substation battery
voltage for up to two battery systems. The SEL-411L,
SEL-421, SEL-451 support two battery monitors while
the SEL-487B, SEL-487E, and SEL-487V support one.
Each battery monitor supports programmable threshold
comparators and associated logic provides alarm and
control for batteries and chargers. The relay also provides
dual ground detection. Monitor dc system status alarms
with an SEL communications processor and trigger mes-
sages, telephone calls, or other actions.
The measured dc voltage is reported in the METER display
via serial port communications, on the LCD, and in the
event report. Use the event report data to see an oscillo-
graphic display of the battery voltage. Monitor the sub-
station battery voltage drops during trip, close, and other
control operations.

Schweitzer Engineering Laboratories, Inc. SEL-421-7 Data Sheet
19
Breaker Contact Wear Monitoring
Circuit breakers experience mechanical and electrical wear
during each operation. Effective scheduling of breaker
maintenance takes into account the manufacturer’s pub-
lished data of contact wear versus interruption levels and
operation count.
➤Every time the breaker trips, the relay integrates
interrupted current. When the result of this integration
exceeds the threshold set by the breaker wear curve
(Figure 24), the relay can alarm via an output contact
or the optional front-panel display. With this
information, you can schedule breaker maintenance
in a timely, economical fashion.
➤The relay monitors last and average mechanical and
electrical interruption time per pole. You can easily
determine if operating time is increasing beyond
reasonable tolerance and then schedule proactive
breaker maintenance. You can activate an alarm
point if operation time exceeds a preset value.
The relay also monitors breaker motor run time, pole dis-
crepancy, and breaker inactivity.
Diagrams and Dimensions
Figure 24 Breaker Contact Wear Curve and Settings
kA Interrupted
(Set Point 1)
(Set Point 2)
(Set Point 3)
Breaker Manufacturer's
Maintenance Curve
Close to Open Operations
Figure 25 4U Front Panel, Panel-Mount Option
RESET
TARGET
TRIP
ENABLED
SCHWEITZER
ENGINEERING
LABORATORIES
PORT F
ESC ENT
SEL-421
PROTECTION AUTOMATION CONTROL
79 LOCKOUT
ZONE 4
ZONE 2
ZONE 3
ZONE 1
BKR FAIL
BKR CLOSE
SOTF
TIME
COMM
INST
51
79 RESET
50
25 SYNCH
79 CYCLE
GROUND
PHASE B
PHASE C
PHASE A
IRIG LOCK
PMCU OK
LOP
OSB
SPT
ENABLED
COMM
SCHEME
ENABLED
ALT
SETTINGS
RELAY
TEST
MODE
MANUAL
CLOSE
ENABLED
RECLOSE
ENABLED
AUX 1
AUX 2
AUX 3
AUX 4
BREAKER
CLOSED
BREAKER
OPEN
i7285a

SEL-421-7 Data Sheet Schweitzer Engineering Laboratories, Inc.
20
Figure 26 SEL-421-7 SV Subscriber 4U Rear Panel, High-Speed INTC (200 Slot) Interface Board
Five-port Ethernet card ordering option depicted.
PORT 1
PORT 2
EIA-232
PORT 3
1
9
1
9
1
9
TIME IRIG–B
BAY 2 BAY 3 BAY 4
BAY 1
196-1921.A
i7285a
31
GND
302928
27
2625
+/H –/N
POWER
–
+
Vdc 2
+
Vdc 1
MONITOR
–
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
09
08
07
06
05
04
03
02
01 B
200
B
200 ++++++++
OUT01 OUT02 OUT03 OUT04 OUT05 OUT06 OUT07 OUT08 OUT14 OUT15OUT09 OUT10 OUT11 OUT12 OUT13
+++++
IN01 IN02 IN03 IN04 IN05 IN06 IN07 IN08
ACT LNK
100M
PORT 5E
ACT LNK
PORT 5D
ACT LNK
PORT 5C
ACT LNK ACT LNK
PORT 5B
100/1000M
PORT 5A
ZZ
Figure 27 SEL-421-7 SV Publisher 4U Rear Panel, High-Speed INTC (200 Slot) Interface Board
Figure 28 SEL-421-7 TiDL 4U Rear Panel
Five-port Ethernet card ordering option depicted.
PORT 1
PORT 2
EIA-232
PORT 3
1
9
1
9
1
9
TIME IRIG–B
BAY 2 BAY 3 BAY 4
BAY 1
196-1921.A
i7285a
31
GND
302928
27
2625
+
/H
–
/N
POWER
–
+
Vdc 2
+
Vdc 1
MONITOR
Z
–
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
09
08
07
06
05
04
03
02
01 B
200
B
200 ++++++++
OUT01 OUT02 OUT03 OUT04 OUT05 OUT06 OUT07 OUT08 OUT14 OUT15OUT09 OUT10 OUT11 OUT12 OUT13
+++++
IN01 IN02 IN03 IN04 IN05 IN06 IN07 IN08
ACT LNK
100M
PORT 5E
ACT LNK ACT LNK
PORT 5DPORT 5C
ACT LNK
PORT 5B
ACT LNK
100/1000M
PORT 5A
IBWIAW ICW IAX IBX ICX
01 02 03 04 05 06 07 08 09 10 11 12
Z
VAY VBY VCY VBZVAZ VCZ
13 14 15 16 17 18 19 20 21 22 23 24
Five-port Ethernet card ordering option depicted.
PORT 1
PORT 2
EIA-232
PORT 3
1
9
1
9
1
9
TIME IRIG–B
BAY 2 BAY 3 BAY 4
BAY 1
31
GND
302928
27
2625
+/H –/N
POWER
–
+
Vdc 2
+
Vdc 1
MONITOR
Z
–
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
09
08
07
06
05
04
03
02
01 B
200
B
200 ++++++++
OUT01 OUT02 OUT03 OUT04 OUT05 OUT06 OUT07 OUT08 OUT14 OUT15OUT09 OUT10 OUT11 OUT12 OUT13
+++++
IN01 IN02 IN03 IN04 IN05 IN06 IN07 IN08
i7285a
ACT LNK
100M
PORT 5E
ACT LNK ACT LNK
PORT 5DPORT 5C
ACT LNK
PORT 5B
ACT LNK
100/1000M
PORT 5A
EN AL
PORT 6A
EN AL
PORT 6B
EN AL
PORT 6C
EN AL
PORT 6D
EN AL
PORT 6E
EN AL
PORT 6F
EN AL
PORT 6G
EN AL
PORT 6H
TiDL CONNECTIONS ONLY