4.5.10.4 Operation principle
The function can be enabled and disabled with the
Operation
setting. The
corresponding parameter values are “On” and “Off”.
The operation of VVSPPAM can be described by using a module diagram. All the
modules in the diagram are explained in the next sections.
Figure 364: Functional module diagram
Vector shift detector
This module measures the duration of each cycle of the voltage signal phase. The
duration of the present cycle is compared to the previous cycle, considered as
reference. When the mains is lost, a sudden change is seen in the cycle length,
if loading of the generator changes suddenly and power mismatch or unbalance
(generation vs. load) in the islanded part of the network is large enough. The cycle
shifts with time, that is, the frequency may not change but a vector shift is seen in
phase as shown in
Figure 365
.
This step is measured in degrees for each voltage signal defined by the
Phase
supervision
setting. The
Phase supervision
setting determines which voltage is
used for detecting vector shift. The available
Phase supervision
options are “All” and
“Pos sequence”. If the calculated value of Δδ exceeds the set
Start value
setting for
all the defined phases, the module sends an enabling signal to start the Pulse timer.
The
Voltage selection
setting is used to select whether the available voltage signal
is phase-to-earth or phase-to-phase voltage.
The recommended and the default value for
Phase supervision
is “Pos
sequence”.
If the magnitude of the voltage level of any of the monitored voltage signal, defined
by the
Phase supervision
setting, drops below
Under Volt Blk value
or exceeds
Over
Volt Blk value
, the calculation of vector shift is disabled and the INT_BLKD output is
activated.
The function is blocked and LOWAMPL_BLKD is activated, if the measured frequency
deviates ±5% from the nominal value.
The magnitude of calculated vector shift for three phase-to-earth or phase-
to-phase voltages, USHIFT_A_AB, USHIFT_B_BC and USHIFT_C_CA or positive
sequence voltage U1SHIFT, which resulted in the activation of last OPERATE output,
are available in the Monitored data view.
The activation of BLOCK input deactivates the INT_BLKD output.
Protection functions
1MRS757644 H
696 620 series
Technical Manual
To Next Page
Loading...
