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