ABB RELION REX640 Technical Manual page 505

1MRS759142 C
REX640
Technical Manual
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Figure 273: 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 = ∠ −
(
− ∠ −
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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 Characteristic angle setting must be
changed. This can be done automatically with the RCA_CTL input, which results in
the addition of -90° in the Characteristic angle setting.
The value (ANGLE_RCA) is available in the monitored data view.
Protection functions
)
Section 4
(Equation 63)
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