R
0E
R
0
1
X
m0
2
R
0
2
X
0
2
+
--------------------------
+
è
ø
ç
÷
æ
ö
×
=
EQUATION561 V1 EN-US
(Equation 342)
X
0E
X
0
1
X
m0
2
R
0
2
X
0
2
+
--------------------------
–
è
ø
ç
÷
æ
ö
×
=
EQUATION562 V1 EN-US
(Equation 343)
7.12.3.6
Setting the reach with respect to load
GUID-ED84BDE6-16CD-45ED-A45D-5CFB828A9040 v4
Set separately the expected fault resistance for phase-to-phase faults
RFPP and for the phase-
to-earth faults
RFPE for each zone. For each distance zone, set all remaining reach setting
parameters independently of each other.
The final reach in the resistive direction for phase-to-earth fault loop measurement
automatically follows the values of the line-positive and zero-sequence resistance, and at the
end of the protected zone is equal to equation
(
)
1
R
2 R1 R0
RFPE
3
=
×
+
+
IECEQUATION2303 V1 EN-US
(Equation 344)
2 X1 X0
arctan
2 R1 R0
loop
j
×
+
=
×
+
é
ù
ê
ú
ë
û
EQUATION2304 V1 EN-US
(Equation 345)
Setting of the resistive reach for the underreaching zone 1 should follow the condition to
minimize the risk for overreaching:
RFPE
4.5 X1
£
×
IECEQUATION2305 V1 EN-US
(Equation 346)
The fault resistance for phase-to-phase faults is normally quite low compared to the fault
resistance for phase-to-earth faults. To minimize the risk for overreaching, limit the setting of
the zone1 reach in the resistive direction for phase-to-phase loop measurement based on the
equation.
RFPP
X
≤ ⋅
6
1
IECEQUATION2306 V2 EN-US
(Equation 347)
The setting
XLd is primarily there to define the border between what is considered a fault and
what is just normal operation. See figure
In this context, the main examples of normal
operation are reactive load from reactive power compensation equipment or the capacitive
charging of a long high-voltage power line.
XLd needs to be set with some margin towards
normal apparent reactance; not more than 90% of the said reactance or just as much as is
needed from a zone reach point of view.
As with the settings
RLdFw and RLdRv
[2]
,
XLd is representing a per-phase load impedance of a
symmetrical star-coupled representation. For a symmetrical load or three-phase and phase-to-
Section 7
1MRK 505 343-UEN B
Impedance protection
318
Application manual
Содержание Relion 670 series
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