Schweitzer Engineering Laboratories SEL-749M, Instruction Manual

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4.35
Date Code 20080918 Instruction Manual SEL-749M Relay
Protection and Logic Functions
I/O Configuration
ULTRIP UNLATCH TRIP CONDITIONS SEL
OGIC
EQUATION
Following a fault, the trip signal is maintained until all of the
following conditions are true:
➤
Minimum trip duration time (TDURD) passes.
➤
The TR SEL
OGIC
control equation result deasserts to logical 0.
➤
All the motor lockout functions, described below, deassert to
logical 0.
➤
One of the following occurs:
➢
Unlatch Trip SEL
OGIC
control equation setting
ULTRIP asserts to logical 1.
➢
Target Reset SEL
OGIC
control equation setting
RSTTRGT asserts to logical 1.
➢
Target Reset Relay Word TRGTR asserts. The TRGTR
is asserted when the front-panel
{RESET}
pushbutton is
pressed or a target reset serial port command is
executed (ASCII, Modbus, or DeviceNet).
➢
An EMERGENCY RESTART command is executed
or the EMRSTR SEL
OGIC
control equation setting
asserts to logical 1.
Lockout After Stop
The relay automatically locks out the motor by asserting the trip
signal under any of the following conditions:
➤
Antibackspin Lockout. The ABSDLY timer has not expired
since the motor trip occurred. The trip signal is maintained until
the ABSDLY timer expires.
➤
Minimum Time Between Starts Lockout. A new start is not
permitted until after the minimum time between starts has
passed. The trip signal is maintained until a start is permitted.
➤
Starts-Per-Hour Limit Lockout. If the starts-per-hour limit
has been met, a new start is not permitted until 60 minutes after
the oldest start. The trip signal is maintained until a start is
permitted.
➤
Thermal Element Lockout. The motor thermal element
% Thermal Capacity Used (TCU) value is too high to permit a
normal motor start without tripping. The trip signal is
maintained until the % Thermal Capacity decreases to a level
where a start can safely take place.
Figure 4.21 Thermal Element Lockout Logic
If any of the above protection functions is not enabled by the relay
settings, that function does not affect trip unlatch.
NOTE:
Factory-default setting of
the ULTRIP provides a manual reset
of the protection trips. Set the
ULTRIP := 1 if you want an automatic
reset. You can make the automatic
reset by a selected element; for
example, set ULTRIP := F_TRIG 49T
in a two wire motor control circuit.
100 — TCSTART
TCU
Relay
Word Bit
THERMLO
TDSTART Start inhibit level setting in percent
TCU
Thermal capacity used in percent
Note: This diagram is valid when the motor is stopped and 49T = 0
(49T is a Thermal Trip Relay Word bit).
Courtesy of NationalSwitchgear.com