See the preprocessing function blocks in this document for the possible
signal sources.
There are a few special conditions which must be noted with the configuration.
Table 861: Special conditions
Condition Description
U3P connected to real measurements The function can work with any two voltage
channels connected but it is recommended
to connect all three voltage channels.
Improper analog channel configuration causes a validation error if the analog
channels are not completely configured or they do not match with certain settings.
For troubleshooting, check the contents of this chapter and also the preprocessing
blocks in this document. The configuration can be written to the protection relay
once the mismatch is corrected.
4.5.9.5 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.
OPERATE
BLOCK
INT_BLKD
U3P
Vector
shift
detector
U_A_AB
U_B_BC
U_C_CA
Pulse timer
Figure 509: 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 510
.
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.
1MRS759142 F
Protection functions
REX640
Technical Manual
909
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