8
Description
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 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 func-
tions, 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 cur-
rents 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/Instantaneous
(LSI)
Long Time/Short Time/Ground Fault
(LSG)
Long Time/Instantaneous/Ground Fault
(LIG)
Long Time/Short Time/Instantaneous/
Ground 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).
Electronic Trip Units For Siemens SB Encased Systems Breakers
Additional optional features include:
Display Module for local current monitoring (field addable)
Zone Selective Interlocking
Communications for remote monitoring
Electronic Trip Unit Adjustment Panel (2000A illustrated)
Summary of Contents for SBA 1200
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