Description
Electronic Trip Units For Siemens SB Encased Systems Breakers
Information
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 Sys
tems 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 adjust
able protection functions, the trip unit is designed to use
field interchangeable rating plugs. These rating 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
connections or control power to perform its protection
functions.
Overcurrent Protection Configurations
Trip units are available in six basic overcurrent protection
configurations to meet specific protection requirements. All
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/I nstantaneous
(LSI )
Long Time/Short Time/G round Fault
(LSG)
Long Time/Instantaneous/Ground Fault
(LIG)
Long Time/Short Time/Instantaneous/
G round Fault
(LSIG)
As standard features, the trip unit has two built-in-test
functions 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 properly
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 identification 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).
8
Additional optional features include:
Display Module for local current monitoring (field addable)
Zone Selective I nterlocking
Communications for remote monitoring
3.5
2
5
8
7
Short
Time
Pickup
XI,
·07
Short
Time
·1
Delay
.15
�
e
��
1,
.2
Pt
4
5
Pickup
2
7
xl,
10
9
23
24
����
nd
21
26
Pickup
30
28
Delay
.5
.4
Pt
@.Sin
.
�.
TEST
Meter
lA
Is
Display
Module
Amps
90
80
Load Monitor
Alarm Set Points
%
Continuous Amps
Electronic Trip Unit Adjustment Panel
Rating Plug
Curve
Adjustments
Built-in
Test Functions
_Plug-in
Display Module
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