ABB RELION 620 Series Technical Manual page 664

Section 4
Protection functions
4.5.5.4
658
The function starts when the residual voltage exceeds the set limit. ROVPTOV
operates with the definite time (DT) characteristic.
The function contains a blocking functionality. It is possible to block function outputs,
the definite timer or the function itself, if desired.
Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of ROVPTOV can be described by using a module diagram. All the
modules in the diagram are explained in the next sections.
A070748 V2 EN
Figure 334: Functional module diagram
Level detector
The residual voltage is compared to the set Start value. If the value exceeds the set
Start value, the level detector sends an enable signal to the timer. The residual voltage
can be selected with the Uo signal Sel setting. The options are "Measured Uo" and
"Calculated Uo". If "Measured Uo" is selected, the voltage ratio for Uo-channel is
given in the global setting Configuration/Analog inputs/Voltage (Uo,VT). If
"Calculated Uo" is selected, the voltage ratio is obtained from phase-voltage channels
given in the global setting Configuration/Analog inputs/Voltage (3U,VT).
Example 1: Uo is measured from the open-delta connected VTs (20/sqrt(3) kV : 100/
sqrt(3) V : 100/3 V). In this case, "Measured Uo" is selected. The nominal values for
residual voltage is obtained from the VT ratios entered in Residual voltage Uo:
Configuration/Analog inputs/Voltage (Uo,VT): 11.547 kV:100 V. The residual
voltage start value of 1.0 × Un corresponds to 1.0 × 11.547 kV = 11.547 kV in the
primary.
Example 2: Uo is calculated from the phase quantities. The phase VT-ratio is 20/
sqrt(3) kV : 100/sqrt(3) V. In this case, "Calculated Uo" is selected. The nominal value
for residual voltage is obtained from the VT ratios entered in Residual voltage Uo:
Configuration/Analog inputs/Voltage (3U,VT): 20.000kV : 100V. The residual
voltage start value of 1.0 × Un corresponds to 1.0 × 20.000 kV = 20.000 kV in the
primary.
1MRS757644 F
620 series
Technical Manual