ABB RELION REX640 Technical Manual page 1119

1MRS759142 C
REX640
Technical Manual
SCEFRFLO can also determine the value for the Ph capacitive React setting by
measurements. The calculation of Ph capacitive React is triggered by the binary signal
connected to the TRIGG_XC0F input when an earth-fault test is conducted outside the
protected feeder during commissioning, for example, at the substation busbar. The
Calculation Trg mode has to be "External". After the activation of the TRIGG_XC0F
triggering input, the calculated value for setting Ph capacitive React is obtained from
recorded data as parameter XC0F Calc. This value has to be manually entered for the
Ph capacitive React setting. The calculated value matches the current switching state
of the feeder so if the switching state of the protected feeder changes, the value should
be updated.
Figure 604 shows an example configuration, which enables the measurement of
setting Ph capacitive React.
GUID-8033991A-6B91-4B31-A9C3-00AEAD7EAFE3 V1 EN
Figure 604: An example configuration, which enables the measurement of
setting Ph capacitive React
If the earth fault is detected by the residual overvoltage function (START of
ROVPTOV), but not seen by the forward-looking earth-fault protection function
(START of DEFLPDEF), the fault is located outside the protected feeder. This is
mandatory for a valid measurement of setting Ph capacitive React. After a set delay
(TONGAPC), the input TRIGG_XC0F is activated and the parameter XC0F Calc in
the recorded data is updated. The delay (TONGAPC) must be set longer than the start
delay of the directional earth-fault function DEFLPDEF, but shorter than the
minimum operating time of the directional earth-fault functions in any of the feeders.
For example, if the start delay is 100 ms and the shortest operating time is 300 ms, a
value of 300 ms can be used. Circuit breaker and disconnector status is used to verify
that the entire feeder is measured.
Modeling a non-homogeneous line
A typical distribution feeder is built with several different types of overhead lines and
cables. This means that the feeder is electrically non-homogeneous. SCEFRFLO
allows the modeling of the line impedance variation in the protection relay with three
line sections with independent impedance settings. This improves the accuracy of the
physical fault distance conversion done in the protection relay, especially when the
line impedance non-homogeneity is severe. Each section is enabled by entering a
Protection related functions
Section 5
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