4.12.5.2 Function block
Figure 641: Function block
4.12.5.3 Functionality
The compensated neutral unbalance voltage protection function CNUPTOV detects
overvoltage at the neutral point of the shunt capacitor. A blown fuse or a
shortcircuited capacitor element results in unbalance in the shunt capacitor bank
causing increase in neutral point voltage. With CNUPTOV, an inherent capacitor
bank unbalance which results in non-zero neutral point voltage can be compensated
automatically on a continuous basis.
The function starts when the fundamental (DFT) component of the compensated
neutral unbalance voltage exceeds the set limit. CNUPTOV operates with the
definite time (DT) characteristics.
The function contains a blocking functionality. It is possible to block function
outputs, the definite timer or the function itself.
4.12.5.4 Analog channel configuration
CNUPTOV has three analog group inputs which must be properly configured.
Table 1094: Analog inputs
Input Description
U3P Three phase voltages
URES Residual voltage (measured or calculated)
UNEUT Measured neutral voltage
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 1095: Special conditions
Condition Description
U3P connected real meas-
urements
The function can work with any two voltage channels connec-
ted but it is recommended to connect all three voltage chan-
nels.
URES calculated The function requires that all three voltage channels from ter-
minal side are connected to calculate residual voltage. Setting
VT connection
must be "Wye" in that particular UTVTR.
1MRS759142 F Protection functions
REX640
Technical Manual
1149
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