Specifications

Description
Electronic Trip Units For Siemens SB Encased Systems Breakers
2
Electronic Trip Unit
The Electronic Trip Unit is a microprocessor controlled multi-
function overcurrent protective device for application with
Siemens state-of-the art family of SB Encased Systems
Breakers.The adjustment flexibility provided by the trip unit
allows the user to easily accommodate load changes and
other protective requirements while still assuring optimum
coordination. In addition to the adjustable protection functions,
the unit is designed to use field interchangeable rating plugs.
These ratings plugs allow the ampere rating of the breaker to
be changed to meet specific applications.
For ease of installation and interchangeability in the field, the
trip unit has been designed as a plug-in unit to mount directly
into a SB breaker frame.
Current sensors within the SB breakers provide signal currents
and operating power for the trip unit.Therefore, when the
breaker is closed, the trip unit requires no external connec-
tions or control power to perform its protection functions.
Overcurrent Protection Configurations
Trip units are available in seven overcurrent protection configu-
rations to meet specific protection requirements. Six trip units
have Adjustable Continuous Current and Long Time Delay.
Optional protection configurations are:
Protection Configuration Identifier
Long Time/Short Time LS
Long Time/Instantaneous LI
Long Time/Short Time/Instantaneous LSI
Long Time/Short Time/Ground Fault LSG
Long Time/Instantaneous/Ground Fault LIG
Long/Short Time/Instantaneous/Ground Fault LSIG
Fixed Long Time/Instantaneous MLI
As standard features, the trip unit has two built-in-test func-
tions and a fault identification function. System Check is a
built-in-test function that continuously checks the status of the
microprocessor and protective algorithms. A green LED on
the front panel blinks approximately every 3 seconds when
the microprocessor is correctly cycling through its protection
routines. Integral Test is a built-in-test that allows the user to
exercise the trip unit electronics. LED indicators display the
testing status.Trip Status is a fault identificaton function that
stores information when a fault current causes the trip unit to
trip the circuit breaker. By pressing the Query button the user
can display the cause of the breaker trip by illuminating one of
four LED’s: OL (overload), ST (short time), SC (short circuit), or
GF (ground fault). Newer version trip units are equipped with a
Trip Status LED Reset Button for resetting the trip indicator.
Additional optional features include:
Display Module for local current monitoring (field addable)
Zone Selective Interlocking
Communications for remove monitoring
Full Function Trip Unit
NOTE: Earlier model trip units may use (l
r
) as the Rating
Plug designator and (I
n
) to denote (MAX Rating).The
designations for the current model trip unit are shown
above. Note however, that the change in designation has
no effect on the switch settings used for selecting contin-
uous, Long Time, Short Time, Instantaneous and Ground
Fault pickup and delay values.
n
SYSTEM
CHECK
Continuous
Long
Time
Delay
Rating Plug
l
n
= 1000A
Short
Time
Delay
xl
n
Secs
@8 x l
n
Short
Time
Pickup
8
1.5
2
2.5
3
3.5
4
5
6
7
.3
.07
.1
.15
.2
.3
.07
.1
.15
.2
I
2
t
Fixed
Instantaneous
Pickup
xl
n
10
1.5
2
3
4
5
6
7
8
9
Ground
Fault
Delay
.5
.1
.2
.3
.4
.5
.1
.2
.3
.4
I
2
t
Fixed
MAX RATING
= 2000A
Ground
Fault
Pickup
30
20
21
22
23
24
25
26
27
28
Phase
G.F.
Trip
APM
TEST
TS31
TestingPass
Query
Trip
Status
O.L. S.T. S.C. G.F.
Display
Module
Amps
100
50
60
65
70
75
80
85
90
95
30
2.5
4
5.5
8
10
14
17
21
25
Secs
@6 x l
n
Load Monitor
Alarm Set Points
Continuous Amps
%
90
100
Present Demand
Maximum Demand
I
A
I B
60
70
80
I C
Meter
SIEMENS
I =%I
lg=% MAX
RATING
Secs
@
1000A
r
Rating Plug
Curve
Adjustments
Fault Indicators
Plug-in
Display Module
Built-in
Test Functions