ABB MICRO-51 Manual

August, 1991
Supersedes Descriptive Bulletin 41-123M
pages 1 and 2, dated January, 1991
Mailed to: E, D, C/41-100C
Micro-51
Micro-511FT
Features
Eight selectable curves
•
Wide current tap ranges
•
Exceptional setting resolution
•
Self-powered, low burden
•
ABB Power T&D Company Inc.
Relay Division
Coral Springs, FL
Allentown, PA
Single Phase
Device Number: 50/51
Transient and EMI immunity
•
Total-drawout construction
•
Retrofit existing CO installations
•
2 year warranty
•
U
CIRCUIT SHIELD
Types MICRO-51 and
MICRO-511FT
Microprocessor-Based
Time-Overcurrent
Relays
Application
Micro-51 microprocessor-based overcurrent
relays are used for phase and ground overcur­
rent protection in utility, industrial. and com­
mercial electrical power systems. The Micro-51
operates from conventional 5A or 1 A second­
ary current transformers. The relay is self-pow­
ered from the current; therefore, there is no
continuous drain on the control voltage supply.
Settings are made by front panel switches.
Eight time-current curves are built-in, select­
able on the front panel:
Inverse Long Time Inverse
Very Inverse Long Time Very Inverse
Extremely Inverse Long Time Extremely
Inverse
Definite Time
Short Time Inverse
Wide current tap ranges with exceptional set­
ting resolution are offered: 1.5-12A in 0.25A
increments, and 0.3-2.4A in 0.05A increments.
The time dial is adjustable from 1 to 10 in
increments of 0.1.
An instantaneous element is standard. Instan­
taneous pickup is adjustable from 1 to 20 multi­
ples of the time-pickup, in increments of 0.1
multiples. The instantaneous unit may be dis­
abled by setting the pickup to zero.
The Micro-51 can be set for operation on a 50
Hz or 60 Hz system by positioning an internal
link.
The Micro-51 has three electrically isolated
normally-open output contacts: Time trip, Inst.
trip, and trip alarm.
A led is provided on the front panel to indicate
when the cc;rrent is above the pickup setting.
Two targets are provided for Time and Instan­
taneous trip indication. Target operation is by
trip circuit current. Reset is manual by a front
panel magnetic device.
The Micro-51 has self-diagnostics that continu­
ously perform functional checks when the input
current to the relay is above a minimum level.
The integrity of the ROM, RAM, EEPROM, and
anaglog elements are monitored. A red led on
the front panel indicates the detection of a
problem.
Descriptive Bulletin
41-123M
Page 1
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