ABB Relion 611 Series, Technical Manual

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Time constant start , Time constant normal and Time constant stop settings. Only one
time constant is valid at a time.
Table 143: Time constant and the respective phase current values
Time constant (tau) in use Phase current
Time constant start Any current whose value is over 2.5 x I
r
Time constant normal Any current whose value is over 0.12 x I
r
and all
currents are below 2.5 x I
r
Time constant stop All the currents whose values are below 0.12 x I
r
The Weighting factor p setting determines the ratio of the thermal increase of the two
curves θ
A
and θ
B
.
The thermal level at the power-up of the protection relay is defined by the Initial
thermal Val setting.
The temperature calculation is initiated from the value defined in the Initial thermal
Val setting. This is done if the protection relay is powered up or the function is turned
off and back on or reset through the Clear menu.
The calculated temperature of the protected object relative to the operate level, the
TEMP_RL
output, is available through the monitored data view. The activation of the
BLOCK
input does not affect the calculated temperature.
The thermal level at the beginning of the start-up condition of a motor and at the end
of the start-up condition is available in the monitored data view at the
THERMLEV_ST
and
THERMLEV_END
outputs respectively. The activation of the
BLOCK
input does
not have any effect on these outputs.
Alarm and tripping logic
The module generates alarm, restart inhibit and tripping signals.
When the thermal level exceeds the set value of the Alarm thermal value setting, the
ALARM
output is activated. Sometimes a condition arises when it becomes necessary
to inhibit the restarting of a motor, for example in case of some extreme starting
condition like long starting time. If the thermal content exceeds the set value of the
Restart thermal val setting, the
BLK_RESTART
output is activated. The time for the
next possible motor start-up is available through the monitored data view from the
T_ENARESTART
output. The
T_ENARESTART
output estimates the time for the
BLK_RESTART
deactivation considering as if the motor is stopped.
When the emergency start signal
START_EMERG
is set high, the thermal level is set
to a value below the thermal restart inhibit level. This allows at least one motor start-
up, even though the thermal level has exceeded the restart inhibit level.
1MRS757454 D
Section 4
Protection functions
611 series 149
Technical Manual