the network where overcurrent fault detection supports the directional overcurrent
principle. To determine the direction of fault, directional earth-fault requires a
reference, known as polarizing quantity against which residual current can be
compared. This polarizing quantity can be either a zero sequence voltage or negative
sequence voltage, depending on the network. SIM8F module supports zero sequence
voltage.
Relay characteristic angle
The Characteristic angle known as Relay Characteristic Angle (RCA), Relay Base
Angle or Maximum Torque Angle (MTA), is used in the "Phase angle" mode to turn
the directional characteristic, if the expected fault current angle does not coincide with
the polarizing quantity to produce the maximum torque. That is, RCA is the angle
between the maximum torque line and polarizing quantity. If the polarizing quantity
is in phase with the maximum torque line, RCA is 0°. The angle is positive if operating
current lags the polarizing quantity and negative if it leads the polarizing quantity.
Example 1
If the "Phase angle" mode is selected, the compensated network (ϕ
RCA
= 0°) and
Characteristic angle = 0°.
Maximum torque line
Characteristic angle = 0°
Non-operating zone
Min forward angle
Min reverse angle
Min operate
current
Max forward angle
Max reverse angle
Io
(Operating quantity)
Forward operating zone
Backward operating zone
-Uo
(Polarizing quantity)
Zero torque line
GUID-48ACC602-5393-499A-B92D-8C693243A541 V1 EN
Figure 59: Definition of the relay characteristic angle, RCA = 0° in a
compensated network
Example 2
1MRS757488 H Section 6
Commissioning
RIO600 105
Installation and Commissioning Manual
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