ABB RELION REX640 Technical Manual page 532

Protection functions
Figure 306: Definition of the relay characteristic angle
The phase angle difference is calculated based on the
(also known as Relay Characteristic Angle (RCA) or Relay Base Angle or Maximum
Torque Angle (MTA)). The
of earthing employed in the network. For example, in case of an unearthed network,
the
network, the
angle is selected so that it is close to the expected fault angle value, which results
in maximum sensitivity.
to +180°. Thus, the effective phase angle (ϕ) for calculating the residual power
considering characteristic angle is according to the equation.
φ = ∠ −
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
coil sometimes is temporarily disconnected. When the coil is disconnected, the
compensated network becomes isolated and the
be changed. This can be done automatically with the RCA_CTL input, which results
in the addition of -90° in the
The value (ANGLE_RCA) is available in the monitored data view.
532
Characteristic angle setting is set to -90°, and in case of a compensated
Characteristic angle setting is set to 0°. In general, Characteristic
Characteristic angle can be set anywhere between -179°
(
( Uo ) − ∠ − Io Characteristic angle
Characteristic angle setting is done based on the method
)
Characteristic angle setting.
1MRS759142 F
Characteristic angle setting
Characteristic angle setting must
Technical Manual
(Equation 75)
REX640