Level detector
The Level detector compares the magnitude of the measured apparent power to
the set
Start value. If the measured value exceeds the set Start value, the Level
detector sends an enabling signal to the Timer module.
Directional calculation
The Directional calculation module monitors the direction of the apparent power.
When the apparent power flow is in the operating area, the module sends the
enabling signal to the Timer module. The directional operation can be selected with
the combination of the settings
Directional mode and Power angle. The selectable
options for the
Directional mode setting are "Forward" and "Reverse". The Power
angle setting can be used to set the power direction between the reactive and
active power.
A typical error is, for example, that the VT or CT poles are wrongly
connected. This is seen as a power flow opposite to that of the intended
direction. The
Pol Reversal setting can be used to correct the situation.
By setting the value to "True", the measured apparent power is turned
180 degrees.
Non operating
area
Operating
area
P
Q
Start value
Figure 383: Operating characteristics with the Start Value setting, the Power angle
setting being 0 and Directional mode "Forward"
Protection functions
1MRS757644 H
738
620 series
Technical Manual
