ABB Relion REC615, Техническое руководство

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In case of unearthed network, if the earth-fault current produced by the protected
feeder I
ef
is known, the setting value can be calculated.
Ph capacitive React
U
I
xy
ef
=
⋅
3
(Equation 64)
U
xy
Phase-to-earth voltage
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 and thus, if the switching state of the
protected feeder changes, the value should be updated.
Figure 256
shows an example configuration, which enables the measurement of
setting
Ph capacitive React.
Figure 256: 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 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
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 protection relay with three
line sections with independent impedance settings. This improves the accuracy of
physical fault distance conversion done in the protection relay, especially in cases
where the line impedance non-homogeneity is severe. Each section is enabled by
entering a section length, which differs from zero, to settings
Line Len section A,
Protection related functions 1MRS758755 C
510 REC615 & RER615
Technical Manual