Level
detector 1
Timer 1
OPERATE
ALARM
START
ISHFT
BLOCK
Level
detector 2
Timer 2
Harmonic
selector
t
t
Figure 249: Functional module diagram
Harmonic selector
This module receives the shaft current measurement signal ISHAFT from the
measurement arrangement. The recommended measurement arrangements (axial
shaft CT with resistor or Rogowski coil with integrator) provide a voltage signal
which is amplified for the relay input. The voltage signal is converted to current
inside the function. Alternatively shaft current can be directly measured by relay
current input when CT is used alone.
The operating harmonic component is selected according to the
Select harmonic
setting which is obtained from the commissioning test.
The selected harmonic component from the shaft current measurement is available
in monitored data under
I_SHAFT
. Additionally, each of the available harmonics are
available in monitored data under
I_SHAFT_H1, I_SHAFT_H3
and
I_SHAFT_H5
.
Level detector 1
The module compares the measured shaft current to the setting
Operate start
value, which is set in primary amps. If the level exceeds the set value, a enable signal
is sent to Timer 1 module.
Level detector 2
The module compares the measured shaft current to the setting
Alarm start value,
which is set in primary amps. If the level exceeds the set value, a enable signal is
sent to Timer 2 module.
Timer 1
Once activated, the Timer 1 activates the
START
output. The time characteristics
are according to DT. When the operate timer reaches the value set by
Operate delay
time, the
OPERATE
output is activated. If the fault disappears before the module
generates an
OPERATE
signal, the reset timer is activated. If the reset timer reaches
the value set by
Reset delay time, the operate timer resets.
The activation of the
BLOCK
signal resets the Timer 1 and deactivates the
OPERATE
and
START
outputs.
Protection functions
1MRS759142 F
436
REX640
Technical Manual