ABB RELION Series Technical Manual page 429

1MRS758755 A
REC615 and RER615
Technical Manual
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.
If "Calculated Uo" is selected, the nominal value of residual voltage is
always phase-to-phase voltage. Thus, the valid maximum setting for
residual voltage Start value is 0.577 × Un. The calculated Uo requires
that all three phase-to-earth voltages are connected to the protection
relay. Uo cannot be calculated from the phase-to-phase voltages.
Timer
Once activated, the timer activates the START output. The time characteristic is
according to DT. When the operation timer has reached the value set by Operate delay
time, the OPERATE output is activated. If the fault disappears before the module
operates, the reset timer is activated. If the reset timer reaches the value set by Reset
delay time, the operate timer resets and the START output is deactivated.
The timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operation time. The value is available
in the monitored data view.
Blocking logic
There are three operation modes in the blocking function. The operation modes are
controlled by the BLOCK input and the global setting in Configuration/System/
Blocking mode which selects the blocking mode. The BLOCK input can be controlled
by a binary input, a horizontal communication input or an internal signal of the
Section 4
Protection functions
423