ABB RELION REX640 Technical Manual page 431

1MRS759142 C
REX640
Technical Manual
compensated networks. As a result the characteristic angle is set automatically to suit
the earthing method used. The RCA_CTL input can be used to change the operation
criteria as described in Table 479
Table 479: Relay characteristic angle control in Iosin(φ) and Iocos(φ) operation criteria
Operation mode setting:
Iosin
Iocos
Table 480: Characteristic angle control in phase angle operation mode
Characteristic
RCA_CTL = FALSE
angle setting
-90° φ = -90°
RCA
0° φ = 0°
RCA
Use of the extended phase angle characteristic
The traditional method of adapting the directional earth-fault protection function to
the prevailing neutral earthing conditions is done with the Characteristic angle
setting. In an unearthed network, Characteristic angle is set to -90 degrees and in a
compensated network Characteristic angle is set to 0 degrees. In case the earthing
method of the network is temporarily changed from compensated to unearthed due to
the disconnection of the arc suppression coil, the Characteristic angle setting should
be modified correspondingly. This can be done using the setting groups or the
RCA_CTL input. Alternatively, the operating sector of the directional earth-fault
protection function can be extended to cover the operating sectors of both neutral
earthing principles. Such characteristic is valid for both unearthed and compensated
network and does not require any modification in case the neutral earthing changes
temporarily from the unearthed to compensated network or vice versa.
The extended phase angle characteristic is created by entering a value of over 90
degrees for the Min forward angle setting; a typical value is 170 degrees (Min reverse
angle in case Directional mode is set to "Reverse"). The Max forward angle setting
should be set to cover the possible measurement inaccuracies of current and voltage
transformers; a typical value is 80 degrees (Max reverse angle in case Directional
mode is set to "Reverse").
and Table 480.
RCA_CTL = FALSE
Actual operation mode: Iosin
Actual operation mode: Iocos
RCA_CTL = TRUE
φ
RCA
φ
RCA
Section 4
Protection functions
RCA_CTL = TRUE
Actual operation mode: Iocos
Actual operation mode: Iosin
= 0°
= -90°
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