ABB RELION Series Technical Manual page 368

Section 4
Protection functions
362
In the phasor diagrams representing the operation of WPWDE, the polarity of the
polarizing quantity (residual voltage Uo) is reversed. Reversing is done by switching
the polarity of the residual current measuring channel (See the connection diagram in
the application manual).
If the angle difference lies between -90° to 0° or 0° to +90°, a forward-direction fault
is considered. If the phase angle difference lies within -90° to -180° or +90° to +180°,
a reverse-direction fault is detected. Thus, the normal width of a sector is 180°.
GUID-A665FD59-1AD1-40B0-9741-A5DBFD0D0F2E V1 EN
Figure 189: Definition of the relay characteristic angle
The phase angle difference is calculated based on the Characteristic angle setting
(also known as Relay Characteristic Angle (RCA) or Relay Base Angle or Maximum
Torque Angle (MTA)). The Characteristic angle setting is done based on the method
of earthing employed in the network. For example, in case of an unearthed network,
the Characteristic angle setting is set to -90°, and in case of a compensated network,
the Characteristic angle setting is set to 0°. In general, Characteristic angle is selected
so that it is close to the expected fault angle value, which results in maximum
sensitivity. Characteristic angle can be set anywhere between -179° to +180°. Thus,
the effective phase angle (ϕ) for calculating the residual power considering
characteristic angle is according to the equation.
Uo Io Characteristic angle
( )
(
φ = ∠ − − ∠ −
GUID-D538B6BE-5A4E-4D96-850E-A8555FC57C4A V1 EN
In addition, the characteristic angle can be changed via the control signal RCA_CTL.
The RCA_CTL input is used in the compensated networks where the compensation
)
1MRS758755 A
(Equation 29)
REC615 and RER615
Technical Manual