ABB RELION REX640 Technical Manual page 1149

Protection and control

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1MRS759142 F

Function block

Figure 641: Function block

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.

Analog channel configuration

CNUPTOV has three analog group inputs which must be properly configured.

Table 1094: Analog inputs

There are a few special conditions which must be noted with the configuration.

Table 1095: Special conditions

U3P connected real meas-

URES calculated

Technical Manual

See the preprocessing function blocks in this document for the possible

signal sources.

The function can work with any two voltage channels connec-

ted but it is recommended to connect all three voltage chan-

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.

Three phase voltages

Residual voltage (measured or calculated)

Measured neutral voltage

Protection functions