Siemens Static Trip III Manual

vSIEMENS
Static lTip Ill
lnformation and lnstruction Guide
Builetin SG-31 18-01

Hazardous voltages are present in the equipment
which willcause severe personal injuryand equipment
damage. Always de-energize and ground the equip-
ment before maintenance, Maintenance should be
performed only by qualified personnel. The use of
unauthorized parts in the repair of the equipment or
tampering by unqualified personnel will result in dan-
gerous conditions which can cause severe personal
injury or equipment damage. Follow all safety instruc-
tions contained herein.
Circuit breaker indicators shown in this booklet are for illustration purposes only. Circuit
breakers are to be installed in "Discharged" and "Open" positions only'
IMPORTANT
The information contained herein is general in nature and not intended for specif ic
application purposes. lt does not relieve the user of responsibility to_ use sound
practices in application, installation, operation, and maintenance of the equip-
ment purchased. Siemens reserves the rightto make changes in the specifications
shown herein or to make improvements at any time without notice or obligations,
Should a conflict arise between the general information contained in this publi-
cation and the contents of drawings or supplementary material or both, the latter
shall take precedence.
NOTE
*Authorized and qualified personnel-
For the purpose of'this manual a qualified person is one who is familiar with the
installation, construction or operation of the equipment and the hazards involved.
ln addition, he has the following qualifications:
(a) is trained and authorized to de-energize, clear, ground, and tag circuits
and equipment in accordance with established safety practices'
(b) is trained in the proper care and use of protective equipment such as rubber
gloves, hard hat, safety glasses or face shields, flash clothing, etc', in
accordance with established safety practices.
(c) is trained in rendering first aid.
SUMMARY
These instructions do not purport to cover all details or variations in equipment,
npr to provide for every possible contingency to be met in connection with
installaiion, operation, oi maintenance. Should further information be desired or
should particular problems arise which are not covered sufficiently for the
purchaser's purposes, the matter should be referred to the local sales office,
listed on back of this instruction guide,
The contents of this instruction manual should not become part of or modify any
prior or existing agreement, commitment or relationship The sales contract
contains the entire obligation of Siemens Energy & Automation, Inc. The warranty
contained in the contract between the parties is the sole warranty of Siemens
Energy & Automation, lnc. Any statements contained herein do not create new
warranties or modify the existing warranty.
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a,

Static Trip lll
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Table of Contents
General Information
lntroduction
Overcurrent Protection Conf i gurations
LCD Targets
Communications and Metering Functions
Extended Protective Re aying
Logging Functions
Alarm Output
Remote Open/Close/Trip
Functional Characteristrcs Summary
Principles of Operation
Functional Circuit Description
User Control
Current Sensors
Protective Fau lt Operation
Tripping Actuator
External Power Supply
PT Module
BDU Breaker Display Unit
lsolated lnput/Output
Shadow Protection
lnstallation and Adjustments lnstructions
lnstalling and Removing the Trip Unit
Removing and Replacing Trip Unit Cover
Setting the Overcurrent Protection Adjustments
Trlp Unit Current Shaping Adjustments Curve
Long Time Fault Protection
Long Time Setting
Long Time Delay
Thermal Memory
Short Time Pickup
Short Time Delay
lnstantaneous Fauh Prolect'on
lnstantaneous Pickup
Ground Fault Protection
Ground Fault Pickup
Ground Fault DeLay
Ground Fault Memory Circuit
Constructlng a Time-Current Curve
Ground Fault Sensing Diagrams
Current Sensor Wiring Diagrams
Zone lnterlocking
Metering and Extended Protective Relaying
Measured Parameters Specif ications
Power Flow Sign Conventions
Extended Protectrve Relaying Functions
Current Unbalance
Voltage Unbalance
Under Voltage
Over Voltage
Under Frequency
Over Frequency
Reverse Power
Trip Log
Trip Log Stored Parameters
Alarm Functions
Over Range A arms
Under Range Alarms
Unbalance A arms
Power Factor Alarm
Power Factor Scale
Event Log
Alarm Log
Reca b'at r^g aro Reprogra'nrr ng
Password Protectron
Rerrore N4o1 to" rg and Progra.nn 'ng
Loca IMo. to. 1g ard P'ogramming
Fundamental Conf igurat on Parameters
Address
Baud Rate
Phase Sensor Rating
Ground Sensor Rating
Phase Rotatton
Volts Source
Volts Scale
Volts Mode
kW Dernand Period and Number of Pertods
Comm Trip
Comm Close
Comm Open
Default Values
Source for Configuration Parameters
Static Trip lllC Rear Connectors
Ten-Position Rear Connector
Four-Position Rear Connector
Programmable Settings Integrity Protection
Testing
General
Secondary Current Testing
Test Connections
Long Time Pickup Test
Short Time Pickup Test
lnstantaneous Trip Test
Ground Pickup Test
Long Time Delay Test
Thermal Memory Test
Short Time Delay Test
Ground Time Delay Test
Zone lnterlock Test
Load Indicator Output Test
Tripping Actuator Test
Current Sensor Test
Connections
Continuity Checks
Exitation Test
Sensor Polarity
Prmary Current Testing
Hign Polential ard Megger',Iesting
Breaker Display Unit
Breaker Display Unit
Selecting Operating Mode
Data Mode
Reading l\/etering Data
Reading Maximum and Minimum Values
Reading the Alarm (ALRM) Log
Reading the Trip Log
Program Mode
Entering the Password
Changing the Password
Viewing Oonfiguration Parameters and Set-Points
Setting Configuratlon Parameters and Set-Potnts
Clearlng Min/Max and kWhr/kVARhr Values
LED Display Brightness ConLrol
BDU SeltTest Function
BDU Error Messages
Accessories
Zone Interlocktng Components
Zone lnterlock Expanders
Zone lnterlock Coupler
Sealable Transparent Cover
Power Supplies
Portable Test Set - Type PTS4
Communications Secondary Dtsconnects
Breaker Position Switch
lnterposing Relay
Potential Transformers
Ordering lnlormation
Current Sensor and Accessory Part Numbers
Static Trip lll Part Number Designatrons
Trip Unit Catalog Number Defrnitions
1-4
2
a
3
3
3
4
4
4
4
5-7
5
6
6
6
6
7
7
7
7
7
8-17
B
9
9
10
I1
11
12
12
13
13-14
14
15
L3
It)
16
16-17
18
19
20
21-28
21-22
22
22
22
23
23
z3
IJ
24
24
24
24-25
25
25
25
25
to
zo
26
26
26
lo
zo
27
27
27
27
27
aa
27
tt
27
27
/t-zo
zd
28
28
ao
28
ZO
29-35
29
29
29
29-30
30
30
30
30
31
JI
31
31
3Z
32
aa
JZ
32
aa
JJ
JJ-J4
35
36-43
36
JC)
36
36
37
37
co
3B
ea
39
40
41
42
42
42
+J
44-46
44
44
44
44
AR
45
45
46
46
46
47-49
47
48
49
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General lnformation
u,
lntroduction
The trip units of the Static Trip lll family are microprocessor
controiled overcurrent protection devices for application with
Siemens Type RL series of low voltage power circuit breakers
as well us oilret manufacturer's circuit breakers ln addition to
the basic overcurrent protection functions, Static Trip lll trip
units have af ullcomplement of standard and optional features
lncluded in these features are serial communications, energy
,onltoting and additlonal protective relaying functions This
tutt+eatur6s capability together with programmable flexibility
aiLows for the eisy aOiptalion of new and changing protection
requirements.
A standard feature on all trip units is RMS current sensing'
As opposed to peak-current sensing, RMS sensing mea-
.rr"i if," true heating potential of the current waveform This
allows for more accurate overcurrent protection and eliminates
nuisance tripping due to harmonic distortion of the current
waveform.
There are four basic models of the trip units All models are
interchangeable on any frame rating of Siemens Type RL low
voltage power circuit breakers
.-diu'ti" rtip lll models provide basic overcurrent protection'
. Si;il; irip lllC versions provide the added capabilities of
communications and current metering'
o Static Trip lllCP devices have full power metering
. Siuii" Trib llICPX trip units have extended protective relay-
ing capabilities,
Static Trip lll trip units are also available with a universal
mounting package for retrofit applications The trip units may
O" L."dto retrolt the low voltage circuit breakers of almost
every switchgear manufacturer.
1--
c_
lnstantaneous
Pickup
,s,.
Long Time
Setting DelaY
.*:'li[p:;
xSensor Is@6x
Short Time
Pickup DelaY
+t
LCD Target
lndicator
Fault PickuP LED's
LCD Target
Reset
Overcurrent
Protection
Adjustments
Protection
Selection
Switches
Local BDU
Communications
Porl
Communications
Microprocessor
Watchdog LED
Trip Unit
Catalog
Number
lnterlock Port

General lnformation
Overcurrent Protection Conf igurations
Static Trip lll trip units are available in six basic overcurrent
protection configurations to meet specific protection require-
ments, All trip units have Long Time fault protection with
switchable thermal memory. This is designated by the suffix
identifier T immediately following the letters RMS in the catalog
number designation. AII trip units include the LCD target
indicator and fault pickup LED's. The "-T" suffix after the basic
overcurrent protection identifier shows the LCD target is pro-
vided. Zone interlocking capability is also standard on trip
units with short time or ground fault protection, but additional
components and wiring are required to connect trip units
together into a functioning zone-interlocked system. fhe "2"
suffix indicates zone interlocking capability. Available protec-
tion conf igurations are:
Protection Conf iguration
Long Time/lnstantaneous
Long Time/Short Time
Long Time/Short Time/lnstantaneous
Long Time/lnstantaneous/Ground Fault
Long Time/Short Time/Ground Fault
Long Time/Short Time/l nstantaneous/
Ground Fault
LCD Targets
A custom liquid crystal display (LCD) provides a visual indica-
tion of an overcurrent tripping action. Target retention is
provided by capacitive stored energy in the trip unit, eliminat-
ing the need for batteries. ln addition to the tripping informa-
tion, improper operation of the protection microprocessor is
displayed on the LCD. The displayed legends are:
o OVERLOAD - long time delay tripping
. SHORTCIRCUIT-shorttime delayor instantaneoustripping
. GROUND FAULT - ground fault delay tripping
o DISABLED - watchdog circuit indicates protection micro-
processor not f unctioning properly
Communications and Metering Functions
Static Trip lllC trip units meter and communicate phase cur-
rents; Static Trip IIICP trip units meter and communicate
currents, voltages, power, and energy information. Neutral
and ground current metering is available on both models. (See
table for list of parameters measured.)
A second microprocessor, referred to as the communications
microprocessor, is used in these trip units to implement the
communications and metering functions, A green "Comm
Watch' LED, visible from the front of the trip unit, provides a
visual indication of the operation of the second microproces-
sor. When the control powei is present and the microprocessor
is passing the built-in-test routine, the LED blinks with a half-
second pulse every three seocnds. A burst of pulses also
occurs whenever the trip unit is communicating to a master
device via the RS-485 port at the back of the unit.
The same current sensors, used in the overcurrent protec-
tion function, are used in the current metering function.
Special purpose Potential Transformer (PT) modules are
used in measuring the voltages, (see Accessories section).
The accuracy of the integrated digital metering functions
is comparable to separate traditional analog instrumentation.
O lncluded when ground fault protection specified
@ Requ res "N" option and neutral current sensor
O Only displayed for four wire systems
Two communications ports are available from which to read
the metered data. A port on the front of the trip unit provides
access for local monitoring with the Siemens BDU Breaker
Display Unit, (see Breaker Display Un t section). A port on the
back of the trip unit allows the trip unit to be integrated into
the Siemens ACCESSTT/ electrical distribution communica-
tion system. The metered data can be displayed at a Power
MonitorrNa panel or personal computer. Network communica-
tions are over a shielded twisted pair data bus, SEAbus. The
real-time clock in the trip unit is periodically synchronized with
a master clock in the network for accurate, to the second, time
stamping of events.
Extended Protective Relaying
Static Trip ll|CPX trip units provide the same overcurrent
protection, communications, and metering as the Static Trip
lllCP model plus seven additional protective relaying func-
tions. The protection functions have independent pickup
thresholds and delays. The pickup and delay set-points may
be accessed and set remotely via the communications bus
or locally via the BDU Breaker Display Unit, (see Breaker
Dlsplay Unit section), Adjusting of the set-points is protected
by a password to preventtheir being changed by unauthorized
personnel. Viewing of the set-point values is unprotected.
Identifier
RMS-TI-T
RMS-TS.TZ
RMS-TSI-TZ
RN/S-TIG-TZ
RN/S-TSG-TZ
RMS-TSIG-TZ
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Metering Functions
Measured
Parameiers l\ilodel
iltc iltcP
Phase Current
Avg. Phase Currents
Ground Current O
Neutral Current O oni on1
Phase Voltages O
Avg. Phase Voltage O
Line Voitages
Avg. Line Vo tage
kW Demand
kW Hours
kW Hours Reverse
KVAR
kVAR Hours
Power Factor
Freq uency
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General lnformation
Static Trip lllCPX Protective Relay Functions
Protective
Function Pickup Setting
Range (SET=) Time DelaY
Ranqe (DLY=)
Current Unbalance
Voltage Unbalance
Overvoltage
Undervoltage
Reverse Power
Overfrequency
UnderfrequencY
5-50%
60-660v
60-660v
1 0-2000kw
50-70H2
45-60N2
5 seconds
5 seconds
5 seconds
5 seconds
5 seconds
5 seconds
5 seconds
?
Logging Functions
airi; i;p IllC/CP/CPX modeltrip units include several logging
trn"tion. for recording tripping events, pickup conditions'
af armictivity and mini-mum and maximum measured values
Afi fogg"O datu is accessible via the communications bus'
Most"oj the information can also be read using the BDU
u""".ioty Accurate time-stamping of trip and event log data
Lqrii". fj"tiodic synchronization via the communications bus
,.ilg , master deiice such as the Power Monitor display and
,onfioting device. The logging capabilitieswith type of memory'
u" " ".i i oii tv, an d ti m e - st"im I c h a racte r i sti c s a re s u m m a r i ze d
in the following table:
Remote OPen/Close/TriP
b]:rii" iiip'rtalcptcpx trip units can be wired to open and/or
"ni" un electrically operated circuit breaker on command
tro, u io*". Monitor-il unit or other master device using the
nS +g5 communications port The alarm output is used for the
:o"p"n; iomrano, thereby restricting use for other alarm
tuictiont. The 'trip' command uses the tripping actuator to
oo"n tt " circuit breaker and requires no additional compo-
;;;i.;i*iti;g. Not" that if a bell alarm contact is installed on
ttre clrcuit bre"aker using the "trip" command may cause other
,nint"nO"O functions such as prevention of automatic
thr;;;";; Care should be taken to select either "open" or
itrio" functions to meet the intended application' All open'
close anO trip communication commands are secure to pre-
,enl unintenOed operation, and can be disabled atthe trip unit
Functional Characteristics Summary
The{unctionalcharacteristicsofStaticTripllltripunitsare
.rr*utiruO in the following table The catalog number desig-
"rti".. on tf," front of thd trip unit delineate the trip unit's
l[rir"t"titti"s. An explanation of the catalog number desig-
nuiion is given in the Ordering lnformation section'
l_;
O The non-volatile memory is EEPROM which requ res no batterles and is
unaffected by loss of control power' The actjve memory requires control power
to maintain data.
OTheactua|numberofeventsthatmayberecordeddepencsonmemory
- required foreachtypeof event The nominal numberof recorded events isten'
fvents include pickup active and inactive, circuit breaker positLon change'
alarm setpoint activation and release, and alarm relay activation' The most
recent events are retained
O Onty tne most recent trip event is avallable to the BDU' without time-starnp
information.
o ihlnLrl,* fog information isaduplicateof the EventLog messageassoclated
- *ltn t"iuy acivatlon thereby providing a local readout of whai causedlhe
uf rr, l."f uV to activate. Thls feature provides the flexibillly to read all critical
data trom ine trip unit when the BS-4g5 network cornmuntcations capab lity s
not Oeing used or is not fully implemented by the master device
Alarm OutPut
A;i;d*d'feature on Static Trip lllC/CP/CPX trip units is an
alarm output. Any of the trip unit's measured,parameters can
b" ."t to activateihe output based on threshold and delay set-
poinii. n"ti"ution o{ the output is recorded in the trip unit's
Su"niiog for remote signaling via the communications bus
The trip unit alarm output is a solid state optically isolated
f OOrn f iV signal An interposing relay is required to provide
, tR IZOV u"ilZSV dc NO solid state contact for integration
into af ut, or control schemes (see Accessories section)'
O Fequires additional wiring to meet speclfic appllcation
O Supports optlonal Breaker Display Unit accessory'
@ Included when ground fault protectron specified'
6, Bequires "N" optlon and neutral current sensor'
o O;;; command uses alarm relay output and restricts use for other alarm
- frn"tions. Close command requires electrically operated breaker'
Logging
eharacteristic Trip
lod Event
lod Alarm
l6d Min/Max
l^d
Tvne of l\.4emorv O Non-volatlle Active Active Non-voLati e
lnformation
Stored Last three
tripping Approxl-
mately ten
events 2)
Yes
Last alarm
relay Mrn/Max lor all
real{ime meas-
rrrarl narametert
Time-Stamped
at Trip Unit Yes NO No
ACC essib eVia
BS-485
Comm. Port
Local BDU
Comm. Porl
Yes
Yes O
Yes
No
No@
Yes
Yes
Yes
opt
opt
opt
Self-Powered Overcurrent Protectlon
RMS Sensing
Switchable Thermal MemorY
Ground Fault Protection
LCD Target
Protective Microprocessor Watchdog
Pickup LEDs
lone lnterlochlnq u
opt
opt
l.
BS-485 Communications Port
Breaker DlsPlaY Unit Port a
Communlcations Microprocessor Watchdog
Comm Watch LED
Backup' Shadow" Protection
Trip Log
Alarm RelaY OutPut 0
Trip Unit Status lndrcation
Breaker Posttion Indication
Breaker OPeration Counter
Communication OpenlCloseiTrip OO
Event Log
Phase Current Meterlng
Ground Current Metering @
Neutral Current Meterlng G)
Power IVeterlng Functions
Min/Max Power Log
Extended Protective RelaYing
Extended TriP Log

Principles of Operation
v
Y
Functional Circuit Description to the overcurrent fault protection functions. Trip units with
Static Trip lll trip units use microprocessors to execute the communicationscapabilitieshaveanadditional microprocessor
numerical and logic operations of the fault protection, meter- and memory which executes the communications, metering,
ing, and communications functions, The protection micropro- and extended protection functions.
cessor and its associated memorycircuits are totally dedicated
Basic Overcurrent Protection
N,4icroprocessor
Current
Sensors
Static Trip lll nip Unil
Static Trip lll Tripping System Functional Block Diagram
Basic Overcurrent Protection
Microprocessor
Communications & lvleter ng
Microprocessor
External
15V dc
Breaker
Control
Wiring
Twisted Pair To
Master Device
- For CP/CPX Models
Static Trip lllC/CP/CPX Tripping System Functional Block Diagram
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Principles of OPeration
v
User Control
iil'";lt;i*;nts and switches on the trip unit's,face and the
progiur;ing via the c-ommunications ports allow the user
control of the trip ,n't gy these means the user selects the
irr"ii"ur valuei and sofiware routines' stored in the memory
"n"ritr, it-,urrre to be used by the microprocesso-rs in perform-
i." ir-l.ii functions. The selection and programming process
i ;.tI;r;"".1g"'"0 i" L" straignt forward and user f riendlv to
inl*J"gt"; thi tt"," lnt"in,l op"eration of the trip unit is totally
transparent to the user'
Current Sensors
6rii".i"*ioita for fault protection and metering are derived
from special purpose "*["tt sensors mounted in the circuit
breaker. These current sensors are toroidal current transform-
"i.-n. prl.i"e Oeuices if'ey provide high reliability with mini-
,rr'.i6.ri "iror. The rated primarv "'ll:!l^:f the sensors
establish the maxrmum "ontin'o" cLrrent rating of the circuit
breaker, The rated .""6nOuty current for the sensors is 0 5
2mnores at rated o'imutv C'it"nt Atl the sensors used with
Silil fnoil, tio ,iiLt ,,.,j""tapsulated in polvme'ic material
i";;"i"Jt ir'," *inoingt-and prevent motion during a short
circuit fault condition.
ThecurrentSenSorSprovideoperatingpoweraSwellas
"r""ni level data lietetoie wnen tre circurt orgallr;1
;;ili"g load currents, Static Trip lll trip urits requrre no
external connections oi "ontror power to perform iheir basic
overcurrent protective f unctions'
Protective Fault OPeration
il;t.ril;;i.;i;u otiLt o"t"tiption of the process forovercurrent
fault orotection. lhe pio"".r [or Ine extended protective
relaying functions is very similar'
The current signals from the sensors are converted to digital
";[u*s-ov i-resistor network and analog to digital conver-
i;. fn/bti in the trip '"li irt" disital voltases are stored
in temporary memory and are used by the^microprocessors
in detecting and procesling-o'etc"ient conditions and in
metering,
The orotectron microprocessor reads the temporarily stored
;i;:,5i;;il;"t u.i"""'p't"t ir'";' values w'tn the set or
;;Yr;; "oiiJtpo^o'ns to the setting selected bv the use''
When an overcurrent condition is detected' the micropro-
iu..o|.[.oti*ul." begins to process the appropriate protec-
l"tlr""tL". During t6e Iroc'essing of the protection function'
the microprocessor continues to monitor the incoming cur-
rent level data lt tn" ou"L*t"nt condition continues until
thetrrocessingtscompletedandtheappropriatedelaytime
;;."";.; I itppi"s command is.tssued by the mtcropro-
;;;#" T;" tripping" command from the..microproces-
sor causes an output signaf io be sent to a coil in the tripping
actuator,
TripPing Actuator
When the circuit breaKer is closed' the tripping actuator is held
* ; "h";g;; position by a permanent magnet The output
;ig;rl ilil-in6 trip uniiLnelgizes a coil inside the acluator
causinq the nagnetrc ti'^ to siitt to a new path This releases
;h"*;i;;"; ;.;rgv of a spting, also located inside the actuator'
,.O"tte. til "i6rit Ot"Ir''"'"Wh"n the circuit breaker mecha-
nism opens, tn" a"t'Jioi is automatically reiurned to the
charged-and rrero posiliJn oy a reset mechanism A second
coil inside tfre tripping'att'utdt is used to augment the holding
power of the permanenimagn-et during high short circuit con-
ditions so that .truy 'ugn"tic fietds witl nol cause unintended
;i";.;;t ;;mugn"ti'ition while the trip unit is in short time
delay (US Patent issued)
Current Sensors
Tripping Actuator (bottom view)

Principles of Operation
Y
v
External Power Supply
Static Trip lllC/CP/CPX model trip units require external 15V dc
control power for the communications microprocessor. This
allows communication with the trip unit during all load current
conditions, even with the circuit breaker switched off. lnternal
isolation prevents wiring faults from damaging the trip unit's
protective circuits.
PT Module
A special purpose potential transformer assembly is used to
supply voltage signals to Static Trip lllCP/CPX model trip units
and provide isolation from the primary circuits, Class CC 1A
600V fuses are used to protect against internal PT module
faults. The PT modules are encapsulated in polymeric material
to protect the transformer windings and withstand mechanical
vibration when mounted directly on the circuit breaker, The PT
module primary inputs are from the three phases plus neutral.
For 3-wire systems, the neutral conductor input is not used.
BDU Breaker Display Unit
The BDU accessory provides a local means of reading data
from and programming Static Trip llIC/CP/CPX model trip
units. lt contains its own microprocessor which controls the
display and communicates with the trip unit using the local
BDU communication port. Power to operate the LED display
and microprocessor circuitry is derived from the trip unit
through this same port.
lsolated lnput/Output
lnput for a 52b breaker position switch and outputs for Alarm
(output 1) and Close Breaker (output 2) are optically isolated
to protectthetrip unit's internal protection circuitsfrom external
wiring faults. These outputs are rated I00mA 12Y and require
an interposing relay to integrate these control signals into the
desired breaker wiring.
Shadow Protection
The overcurrent protection functions are enhanced by the
communications microprocessor, The protection micropro-
cessor operates totally independent of the communications
and metering functions. Should communications or metering
processing fail, the protection functions will remain fully opera-
tional, However, the communications microprocessor is pro-
grammed to provide backup or "shadow" fault protection. The
"shadow" protection curve is defined by pickup and delay
values slightly above the highest available settings for Long
Time and Short Time functions, In the unlikely event of a
protection microprocessor failure, the communications micro-
processor will execute the overcurrent protection functions.
Long
Time
o
E
Current
Short
Shadow Protection
Y

I nstallation and Adjustments lnstructions
Hazardous Voltage.
Will cause severe iniurY or death'
Turn power ott and lock out suPPlY-
ing device before installing or
removing triP unit.
CAUTION: Before instatling or removing the trip unit' the
;;;rii Lreaker should be p'iaced in the open position with
ttre mectranism dischargel. Drawout breakers should be in
the disconnected Position.
The Static Trip lll trip unit mounts onto a slide{ype bracket
at if,e nwer right side of Siemens Type RL circuit breakers
[Not" illuit"t6fit version trip unit does not include a sl]de
IracXet Also, retrof it of standard trip un it to other manufacturer's
breakers may use different locations')
lnsert the BDU and/or zone
trip unit. interlock cables at
Use the reverse procedure to remove the trip unit from the
circuit breaker,
3,) Secure the trip unit with a single (1) #6 - 32 mountlng screw
8
+r flion the termina block fanning strip wlth the termrnal block and
' ."Jr," it wlth the erqht (B) #6 - 32 slotted head screws'
5.) Beplace the terminal block cover
1.) Remove lhe lerm.ral block cove"
2.) Align the trip unit and slide it all the way onto the bracket
7 ) lnsert the appropriate communications and PT module connectors
' ' ;t;;;;;;t "f ine irip unit lnstallation of the trip unit is now complete'

lnstallation and Adjustments lnstructions
v
v
Removing and Replacing the
Trip Unit's Transparent Cover
The current protection adjustments on the front panel of the
trip unit can be secured against tampering by a plexiglass
transparent cover (see Accessories section).
1) Prior to setting the adjustments, the transparent cover must be
removed. All that is required to remove the cover is to remove the
two nylon seaiing screws that hold it in place.
2.) Afler the adjustments have been set to the desired posrtions,
the cover should be replaced and a wire may be lnserted.
3.) After insertlng the wire, secure with a lead seal to prevent tampering
Setting the Overcurrent Protection Adjustments
The trip unit executes its overcurrent protection functions
based on the current sensor rating and the settings of the
current protection adjustments. Therefore, care should be
taken by the user to make proper sensor selection and adjust-
ment settings,
CAUTION: An adjustment will momentarily revert to its
minimum possible setting whenever a change to the
adiustment is being made. This may cause inadvertent
tripping of the circuit breaker if the adjustment is made
with the circuit breaker in lhe closed position. Therefore,
Siemens recommends that all adjustment changes be
made with the circuit breaker open.
To set an adjustment, place a slotted screw driver onto the
point-to-point adjustment switch and rotate the switch to the
desired setting.
The figure on the following page describes the region of the
time current curve that is being affected by each adjustment.
v

lnstallation and Adjustments lnstructions
Trip Unit Current ShaPing
(Ttris curve is for illustration Adjustments
purposes onlY)
Amperes in Multiples of Long Time Setting
1(1) Long Time Setting Region
The allowable cont nuous operating current ls set to a tractlon of the current
sensor rating
(2) Long Time DelaY Region
The loncl tlme delay s set to an inverse l':t ramp deLay referenced to 6 times the
long t me setting.
(3) Short Time PickuP Begion
'-' if,e st o,t Ime plckup ls set to a muLtiple of the long time setting'
(4) Short Time Delay Region
The short time delay s set to a f lxed delay wlth or wlthout an inverse lzt ramp delay
referenced to 6 times the Long tlme setting
(5) lnstantaneous PickuP Region
Tne 'nS|a^laneo-S Q Cn-P 6 ,". ,o u rrU tiole o. ]he CU.renl Se^So. "aI ng,
(6) Ground Fault Pickup Begion
The ground fauLt pickup . tli'to u percent of the ground current sensor rating
(7) Ground Fault DelaY Begion
The crround fault delay ,. ."i to un inverse l'?t ramp deLay that reverts to a fixed
Ground Current in Percent
of Ground Sensor Rating
100 30010
I
t
o
tao
o
o
CL
o
.1
,OB
.1
08
I
(6)
:J.1.
Ilt
\lt
i1'-t
t{t
10

I nstallation and Adjustments lnstructions
v
v
Long Time Setting
The long time setting establishes the maximum current level at
which the circuit breaker will continuously operate without
initiating a tripping sequence, With the setting switch, the
continuous operating current level may be set to S .55, 6 65
.7, .75, 8, .85 .9 95 or 1.0 times the current sensor rating.
The variance in the tripping sequence pickup due to electronrc
components tolerances is less than 10% The trip units are
designed to accommodate this variance. The pickup is au-
tomatically set by the trip unit to a value that is 10% greater than
the switch setting. Therefore, the actual pickup value will be
between the switch setting and a value 207" grealer than the
switch settings. This ensures that the circuit breaker will
operate continuously at a current corresponding to the switch
setting.
On a Siemens Type RL circuit breaker, the current sensor rat-
ing is given on the circuil breaker rating label located directly
above the trip unit, A similar sensor rating label should be
found when retrofit to other manufacturer's circuit breakers.
Long Time Fault Protection
i nrrn J'rnrr:
LV''\-f r rr l i\/
!;i-r!rrr r\,{ " ., ,.-.,
A ll
i-)
ai
xS*n$or WsO6xSetting
Current in Multiples
of Sensor Rating
.2 3 .4 .5 .6 .7.8.9 l
1 0000
9000
8000
7000
6000
5000
Long time setting set at .B _
Long time pickup will be
between .B and .96 times
the sensor rating.
o
t,
E 4000
o
q)
a
.= 3000
0)
E
F
2000
I 000
Example Long Time Pickup
Crrcu i Breaker Bating Label
Y
11

lnstallation and Adjustments lnstructions
Long Time DelaY
Thelonqtimedelaysetsthetrippingdelayo{thetriounrtbased
on the magnitude of ti'te'ove'i:u're"nt condition The setting of
the long time delay t"r""it on" oflive detay bands The delay
bands are inverse r t tu'it'[ i'ntiiont The lit delay provides a
selective long time p'ot"Jtion brecause the delay is inversely
orooortional to the squaiJoitf-te magnitude of the overcurrent
:f".iiiii," iHl; ;;r.i tnJtiigt.tlt ov"ercurrent conditions have
shorter delays and, conJers6ly' lo*"t overcurrent conditions
have longer delays rn"jo*& uul'"t of the selected band
def ine the minimum o"r"! i"iiit" initiation of lhe 9ircull9.r.?:|<,:
il +i [i .,j "r n " yn"*: :l;'" ii [: fr' ::, fl"J] T J[: ffi :["'fi
m?[i :[ffi; H% ?.. J' ;;'IJ; i ""s t', " rr' " i o*e r -va t u e or
the long time delav ouni illlt"'"nJed to 3 5 6' 1O 17' or 30
seconds at a current "oll".ponJing to 6 times the long time
cpttino Chanqinq tn" f"ong"i-"-t"iting changes the current
i,i -ilY;Hir. " ii*""oit ivt aie rere re nced
IIiJHJ il?#?JXn ,,re raurt protection.is a' rhermar Memorv"
f unction. The purpose oiit-'" If rt"*al Memory function is to
;l;;;i ;d;;&, Flit'tt"nilntermittent overcrrrent condition
rhe [unction mav be ,"t'i'i"JLv placlig ll: ]!:rmal Memorv
"ilt;; "#ih; ittnrot the trip unit to the ln' position
With the function actlvated' the long time delay counter does
not immediately reset t")"i" *n"nih" currentfalls below the
i#n' iil; ilrirp uur'"lJntt"'o' lt counts down at a rate
determined by tne magnit'O"Glt't" remaining current When
there is a persistent i"i"t'it"ti overcurrent that does not
i"#,i," .[;ritime picXuo level, the delay counts are accu-
mulated. Tripping o""'it ;'["nit't"'"""nulatedvalue reaches
the selected long time;;i'; ln1rt" tp""iul,case where the
current drops to n"u'ry #Iihe tong time delay counter does
reset to zero.
Thermal Memory protects against persistant intermittant
overcurrents.
Short Time Fault Protection * , u* ,* s x x s&
Current in MultiPles of
Long Time Setting
1 10
o
E 1oo
o
o
o
a
.;
Elt
'l=
delav band f-
t i z-sdiono
Example - Long Time DelaY Bands
I Long Time DelaY Settlng
L ffi Overcurrent lntervals
' ff P61r"3'Cure'l lnlervals
]
I I count
' oo*''
t'l ,/
$hcri Time
:),:.,r Dt;,ir,v
i-,1,^r,U
i i 11 t't
e8
I
1:l
r l,'f Setlrnq W -':
,) rf
l,!-i
riu
12

lnstallation and Adjustments lnstructions
)>
v
Short Time Pickup Short Time Delay
The short time pickup sets the level of high current the circuit The short time delay sets the tripping delay of the trip unit in
breaker is allowed to carry for a short period of time. This responsetoacurrentinexcessof theshorttimepickupcurrent
pickup, together with the short time delay, allows downstream level. The setting of the short time delay selects one of f ive f ixed
circuit breakers time to clear short circuit faults without trip- delay bands. The lower value of the selected band def ines the
ping the upstream circuit breakers. When the pickup level is minimum delay for the initiation of the circuit breaker tripping.
exceeded, the trip unit initiates the short time fault protection The upper value of the band def ines the maximum time for the
tripping sequence. The short time pickup may be set to 2, 3, 4, clearing of the tripping action including circuit breaker open-
5,6,7 ,8, or 12 times the long time setting. Changing the long ing and arc quenching time. The lower value of the short time
timesettingchangestheshorttimepickupcurrentlevel. delaybandmaybesetto,0S, .15,.22,.30,or,40seconds.
The short time pickup is also implemented to accommodate
possible variances in the tripping sequence pickup value due
to electronic components tolerances. The functional opera-
tion is the same as it is for the long time setting previously
presented. The tolerance is plus 20%/minus 0%.
Current in Multiples
of Long Time Setting
5 10 50 100
.15 second
delay band
I
.22 second
delay band
Example - Short Time Delay Bands (Fixed Delay)
Current in Multiples
of Long Time Setting
2 3 4 5 6 78910
100
50
o
!,
c
o
o
o_^
(,lu
.;
E
tr 5
tt-
LOnO Ilme r
delav h:nrl
JIIUII LII
pickup
aI 4
Ite
set
Drur L urre pruKUp
will be between 4
and 4.8 times the
long time setting.
Example Short Time Pickup
v
13

lnstallation and Adjustments lnstructions
A switch on the f ront of trip units with short time fault protection
;l;;; fotth;."lection of an inverse l'zt ramp function shorttime
O"iry. f " iome applications the l2t delay allows for better co-
orOi,iation with downstream circuit breakers and fuses The
f o*e, uuf r" of the l'?t delay band is preset to a calibrated value
of .5 seconds at a current corresponding to 6 times the long
r;; ;;tti.g Changing the long time setting changes the
"'rt*"i ut"*f,icn t6e "time delay is referenced' At higher
"rrt"ntt the l'?t delay reverts to a fixed delay at the value
selected with the short time delay switch'
Current in MultiPles
of Long Time Setting
10
o
E
o
o
c)
a
'6
E
Example - Short Time Delay Bands with l'?t ramp delay
lnstantaneous Fault Protection
lnstantan00us
Fickup
s
4
2
x Sensor
lnstantaneous PickuP
il;l;;##-ous pltt<up sets the level of hish current at
*r.li"f,l li* ttlp unit will irip the circuit breaker without an
,i""tl""J tinie Jerav. Non-delayed tripping' in response to a
i"u"r" overcurrent condition, mlnimizes potential damage to
"i""ttLri tv.tems and equipment The instantaneous pickup
,ru O" i"tioZ, 4. 6. 8. 12,'or 15timesthecurrentsensor rating'
The pickup is independent of the long time settlng'
The tolerance on the instantaneous pickup is plus 20%/
minus 0%.
Current in MultiPles
of Current Sensor Rating
10
o
t, 10
c
o
o
o
a
.;
E,
F
-9 .1
o
o
I
.01
Long Time
(or Short Time)
delay band
I nstantaneous
Pickup set at 6.
lnstantaneous Pick
will be between 6 0
and 7 .2 times the
current sensor rating
Example - lnstantaneous PickuP
14

lnstallation and Adjustments lnstructions
Y
v
On trip units with both ShortTime and Ground Fault Protection,
the ground fault tripping is inhibited if the trip unit is executing
the short time fault protection sequence.
Ground Fault Pickup
The ground fault pickup sets the level of ground current at
which the circuit interruption sequence is initiated. Together
with the ground fault delay, this setting allows selective tripping
between main and feeder or other downstream circuit break-
ers, The ground fault pickup may be set to 20, 30, 40, 50 or,
60% of the ground sensor rating. The tolerance on the ground
fault pickup is plus or minus 10%.
Note that the ground fault pickup adjustment references the
"Ground Sensor Rating." This gives simple referencing re-
gardless of the type of ground fault scheme used. Further-
more, it allows trip units to be lnterchanged between circuit
breaker frames of all ratings and between different ground fault
schemes. The ground sensor rating appears on the circuit
breaker rating label above the trip unit for residual ground fault
sensing schemes, or on the right side of the circuit breaker
cubicle for direct source or zero sequence type schemes, See
the ground fault sensing diagrams for additional information.
Ground Fault Protection
Ground Fault
Frekup Delay
50 SC ,10
,,1 ^:5
:n
30
)(\
',n Grd Serrsor
Direct Source or Zero Sequence Ground Fault Schemes
10
Ground Current in Percent
of Ground Sensor Rating
EA
JU 100
10
50
o
!,
o
o
o
a
'.
E
tr
I
Ground fault
pickup set at
50%.
Pickup wi I be
between 45 and
Atro/- nf nrnr rnrl
sensor ratrng.
I
Example - Ground Fault P ckup
IY Res dua Ground Fault Schemes
l5

lnstallation and Adjustments lnstructions
Ground Fault DelaY
il," gtornO fauli delay sets the tripping delay of the trip unit in
i""pin." 6 igr.orno current in excess of the ground fault
pi"[rp i"u"f tfrE ground fault delay band is an inverse l2t ramp
iunction that reveits to a fixed delay at the value selected with
if'," gt;unO fault delay switch. The lower value of the l'?t delay
Ouni " presei to a value of .5 seconds at a ground current
"orr"tp,jnJing to t.S times the ground fault pickup The fixed
delay may belet to 10, 25, or .40 seconds'
Example - Ground Fault DelaY Bands
Ground Fault MemorY Circuit
ALt Static Trip lll trip units with ground fault protection come
equipped with a ground fault memory circuit This circuit
efieitivety integraies ground fault currents with time This
p;;;".;. adled pro-tection by preventing the ground fault
delay circuits from being reset when the ground fault currents
u[-ini"tritt"nt and/or erratic. The time constants for the
current integration are preset within the trip unit as a function
of the ground fault delaY.
Constructing a Time'Current Curve
in" toLfo*indinstructions are for constructing a Time-Current
Curve for atrip unitwith long time, shorttime, and instantaneous
Lutt protection, The conslruction of a curve for ground fault
pr-otection or for trip units without short time or without instan-
ianeous fault protection is very similar'
i. Setect the long time setting and delay band to be used'
Example: .6 long time setting
'1O-second delaY band
2. Select the short time PickuP
Example: 4 times the long time setting
lc)
3. Lightly trace a line from the long time pickup point to the
- [i"r#"" point given in the table below for the selected
L""g T*" O"tay"aanO Now darken the line between the
L"g"ti;" ptku6 point and the intersection with the mini-
,ril if-,oti time pickup line; extending the trace' if neces-
tuiy ttf-,it ini"rsection defines the shori time pickup point)
if-li6 fln" i. tf," lower limit of the long time delay band (Note:
*itf',orisf,ott time fault protection the line would extend to
the instantaneous PickuP Point )
L-;pl; - ito, (1, 3b0 sec) to short time pickup point
(The line would Pass through the
reference Point (6x, 10 sec) )
Lono Time Long Time Reference
Dela]r Band PickuP Point l^oinl
5o t,j"onot (1x 1O8O sec) (6x' 30 sec)
i;;;;4. (tx, otz sec) (6x 17 sec)
ro seconOs (tx, gOo sec) (6x' 10 sec)
o r""".0. (tx zto secl (6x, 6 sec)
5.s s"conot (tx, tzo sec) (6x,3 5 sec)
4. Drawavertical linefrom thetop of the graphtothe longtime
pi"frp [oint. This line defines the minimum long time
pickup.
Erur'pf", From (1x, 1OO0O sec)to (1x' 360 sec)
Select the short time delay band to be used'
Example: ,3-second delaY band
Draw a vertical line from the short time pickup point on the
[ng t-" J"f iy line to the selected short time delay This
tlne"defines the minimum short time pickup'
Example: From the short time pickup point to
.3-second time line
Select the instantaneous PickuP'
Example: 12 times current sensor rating
Since the instantaneous pickup is selected with respect to
if-l"irit"nt t"nsor rating, it must be divided bythe long time
pl"t rp to determine its position on the graph'
ExamPle: 12 + .6 = 20
6.
8. Draw a horizontal line along the short time delay line from
- the short time picku p line to ihe instantaneous picku p point'
ihi, tin" is the lower limit of the short time delay band'
f*umpfe' From 4 to 20 along the 3-second time line
9. Draw a vertical line from the instantaneous pickup point to
- th; bottom of the graph This line defines the minimum
instantaneous PickuP.
ir*pll, From (2bx. .3 sec)to (2Ox' 01 sec)
10. The maximum lines of the long time pickup' long time delay
" O""J u.O short time plckufare offset from the minimum
[nbt OV 20%.fhe maximum line of the short time delay
bu;; id .07 seconds greater than the delay setting' Draw
these lines,
i;pi"' a Maximum long time pickup.is a vertical line
trom (1 .2x, 10b00 sec) to (1 2x 360 sec)
b. Maximum long time delay is from (1 2x' 360
sec) to maxiftum short time pickup (4 x
120"k = 4.8). The line would pass through
the new ref eience point (6 x 120% =7 2x' 10
sec)
c Maximum short time pickup is a vertical line
f rom the pickup point to the 37-second time
line.
10
Ground Current in Percent
of Ground Sensor Rating
100 1 000
10
o
E
E
o
o
6)
a
,E
o
E
F
ba
npi
l
I
nd
ck
lllr _H+l
fl-,1T'nn I lll
lrl llll'tDelayband,
{Hf,g?iffm oicxT
11D
minielay mur
-lTt
rl
,\ I
.4 seconc
-delay bal9
..25 seconc
delay banc
lll,ll r';'.:l],:,:',r :" r'
'1*l*1'r
it 1r
t-.1 seconc
delay banc

lnstallation and Adjustments lnstructions
i
lv d.Maximum short time delay is a horizontal lineextendsfromthemaximumvalueoftheshorttimedelay
line along the .37-second time line from the band to .07 seconds, the maximum interrupting time.
maximumshorttimepickuptothemaximum Example: (12+.6)x12A%=24
instantaneous pickup l2.The l2t short time ramp delay may be added to the Time
11.The maximum instantaneous pickup line is a line corre- Current Curve by using previously presented data, see
sponding to a value that is 20% greater than the setting. The Short Time Fault Protection.
Y
Current in Multiples of Long Time Setting
10
.1 100 1 000
1 0000
1 000
100
o
!,
o
I ro
a
.;
E
i=
.1
.01
STEP 4 - Draw minimum-
rong lme prcKup ilne -I
STEPl-Selectlong
time setting and lon(
time delay band
,6
=u Setting
ttttttttt
STEP 10a - Draw maximum
long time p ckup lrne
Long Tlme
Delay
\\
I. STEP 10b - Draw upper limi
/ ot long time delay band
ower lrmil
ay bandof iong time de
STEP 2 - Selecl Qhnrt
;6
)r{
pickup p(;tnt Ileference polnt, (7.2x, 10 sec), for upper
mit of long time delay band (calculated)
te)raw minin
pickup iinr
l
rand
tum
td,;
Short Time
Picku p
Reference polnt (6x, 10 sec), for lower
limit of long time delay band (given)
ll t t t t ttttt t
STEP 10c - Draw maximum short
time pickup Iine
I STEP 6
I short tin
--]_rrr
]TEP 5 - Selecl
;hort time dela\ I t l t i l|l
STEP 12 - Draw short tirne l'?t
ramo delav
='th'; STEP 1Oc
short trm( - Draw upper limit ol delav band
sl
ln
Short lime
Delay
t t|tl
'EP 7 - Select/Ca
ltantaneous picklcr up
S-
of
late
line
EP B - Draw lower limlt
short time delay band STEP1l-I
instantane( lalculate/i lus pickup )raw line maxtmum
215
I nstantaneous
Pickup
|| l]ll
SI
inr
'EP 9 - Draw mrnimum '
itantaneous plckup iine /laxlmum
nterrupting
tlme = .07
111
ttt
ec.
ry
Example Time-Current Curve
17

Ground Fault Sensing Diagrams
Ground Fault Sensing Diagrams
iH"lriiirj^*Ln -0" "oit'g";; to accommodate the followins
oround faulL sensing scnemes'
I 3-Pha.", 3-Wire Residual
. 3-Phase, 4-Wire Residual
. Direct Ground
. ZeroSequence
The following are brief descriptions of the ground f ault sensing
schemes as they r"rutu iJir'5 siatic Trip l'il trip units Detailed
technical and applicatiJn rnfot"tion on the. oround fault
sensino schemes i. "onilin"iln in? s-i"nn"nt rlitrical Prod-
uits Siecitication Guide (SG 3061)'
Residual (3-Phase, 3-Wire) - Under normal system conditions'
(withoul the presence oiu gto;O l'yl.:f ,vector sum of
thenhaseCUrrentsbelngmonitoredbythetripunitiszero.This
i."rf#i;;i;;;; th; Jondition of ah overc.urrent phase-to-
ohase fault and phase t'nOutun"" condrtion When a phase{o-
Xl';;;ii;;ii";i*i, L1"""ioi "' or the phase currents is
Xl;:i,, f t"p"iiiiJi,o tne magnitude or the sround rault rhe
trip unit's microprocessot "Jt this vector sum data in the
execution of the grounJiu* ptt""tion function The trip unit
,illr"tiH" ,i"in"ur nt"ux"i current sensors No external cur-
rent sensors are required'
Circuit breaker current sensors are available with separate
2000A grouno sensor*]iJ'gi t" Orovile-tt1 1200A maxi-
;"u"ri';;";;;-fault pickup '"itins iequired bv NEC Article
230-95 for service "ntt'i"" app-lications Wiring diagrams
for the two 3-Phase, i-Wit" glo'1d fa{! sensing schemes
are given in the Curre'nt'S"ntlot Wiring Diagrams section ln
either case, tr,e curreni t"ntott are ilounGd on the circuit
6t"rx"t. N.i external current sensors are required'
Residual (3-Phase, 4-Wire) - ln the 3 Phase'^4 Wire Residual
scheme a fourth ",""nt-J"nior is connected in the neutral
conductor to Sense"lormat neutrat currents Under normal
svstem conditions tf'e vector sum of the currents in all phases
:'"",;;i.';; .;;i;rl ;r;;;iThis is also true under the condition
;i#;";;"r;[n] pr'tut" io-phase fault and phase unbalance
condition. When a phase-to-ground fault occ-Lrrs' the fault
current returns uiu u putt't"Jtf'Lrif'an tfre neutral' Therefore' the
vector sum of the phaJe currents no longer equals the
neutral current. frris c'lrieni ditferentiat is detected by the
i,",'t.*it *J uied in the execution of the ground fault pro-
i"E,i"" i,l".i,Jn. 6rr.,."ni #n#i wit.t separate 2000A NEC
;;;;;st- ,;;-usable toi t"n's ilnsins scheme' iust as for 3-
pHr.","5 wiie residual giorno sens'ing (see current sersor
Wiring Diagrams),
Direct Ground - ln this scheme' the phase c,urrents are not
used in detecting unO plJ""ittg grornd faults The trip unit
;H.ji;; il;g';,,n0 ti'ii p'Li""iiJ" runcrron based on data
from a ground current Jenloi if ': :"L:.:^t^is located on the
neutral connection to gio'nO at the service,entrance' and is
connected to tne appr6[t't"l"p't terminals on the trip unit
(see Current Sensor Wiring lJiagrams'7
Zero Sequence - This scheme is very similar to the Residual
6"rlirll"i|le traoitionaimethod is touse a core balance tvpe
current sensor wf,icn lncircl6s all phase conductors and
neutral on a four wire tVJ"' UnO"r nolmal :I:t"' conditions
"t " rf.lrt" i"-phase iauti conOltion' there is no output from
;h"'#;r;; i" TH" liip ,"ii o"ta"e the vector sum of the
currents through tne selsor winJow is z.ero.,lf a ground fault
occurs, the ground "'ii"i it not s""n by,the sensor' which
t*,". tl, ,f-rJ *,t"" by I patn ottrer than through the sensor
*"i"d;.1'h;."n.o, oZt"its this current rmbalance and pro-
vides the data requirei'OV jn" tiip unit to execute l? g]"^Y:d
irr["pi"t#i"n lunction The zeto sequence sensor rs con-
nected to the appropiut" inp't t"tminals of the trip unit (see
Crii"nt Sensor'Wirlng Diagrams)'
Alternatively, three orfour current sensors orstandard CT's can
be connected togetnll, " *'tft the Besidual Schemes de-
scribed above. tn tl^'ls JasJ]ho*"u"t' only the electrlcal sum of
the sensor outputs it"it"lj us Jite"t input to the trip unit's
oround fault circuit tlrminats (the sensors are not used for
X;;u. ";;;"i l.prtl"iHills tr'e etectrical equivalent of the
it;;il;;i .ugndti"'"o,,e balance summation'
Breaker Mtd
C!rrefl Sensors
N.!lral Bus
Cur:ent Sensors
Residual Sensing, Circuit Breaker Wiring for Ground Protection (3-
Phase, 4-Wire SYstem Shown)
18
Direct Ground Current Sensing
Aiernate Pcs t on Oi
Zero Seque:.e Sefso'
Nelta D sconnact Lnr
Zero Sequence Ground Fault Protectlon