2.2 Distance protection
73
7SA522 Manual
C53000-G1176-C155-3
8! to activate both criteria for earth-fault detection. This setting can only be
changed via DIGSI
®
at Additional Settings. If you want to detect only the earth cur-
rent, set ,!258! and also 8!7KUHVKROG (address ) to ∞.
Note
Do under no circumstances set address 8!7KUHVKROG to ∞, if you have set
address ()UHFRJQLWLRQ = ,!$1'8! since earth fault detection will
then no longer be possible.
If in isolated or resonant earthed systems the earth fault detection threatens to pick up
due to fault inception transients following the occurrence of a single earth fault, the de-
tection can be delayed with setting address 7,3+$6. Set parameter 7,
3+$6 to ∞ if the earth current threshold can also be exceeded during steady-state
conditions. Then, even with high earth current, no single-phase pickup is possible any-
more. Double earth faults are however correctly detected and measured according to
the preference program (also see Section 2.2.1 at margin heading “Double Earth
Faults in Non-earthed Systems”).
Application with
Series-compensa-
ted Lines
With series-compensated lines (lines with series capacitors), set address 6(5
&203 to <(6 to ensure that the direction determination works correctly in all cases.
The effect of series capacitors on direction determination is described in Sub-section
2.2.2 under margin heading “Direction Determination on Series-compensated Lines”.
Start of Delay Times As was mentioned in the description of the measuring technique, each distance zone
generates an output signal which is associated with the zone and the affected phase.
The zone logic combines these zone fault detections with possible further internal and
external signals The delay times for the distance zones can be started either all togeth-
er on general fault detection by the distance protection function, or individually at the
moment the fault enters the respective distance zone. Parameter 6WDUW7LPHUV (ad-
dress ) is set by default to RQ'LV3LFNXS. This setting ensures that all delay
times continue to run together even if the type of fault or the selected measuring loop
changes, e.g. because an intermediate infeed is switched off. This is also the preferred
setting in the case of other distance protection relays in the power system working with
this start timing. Where grading of the delay times is especially important, for instance
if the fault location shifts from zone Z3 to zone Z2, the setting RQ=RQH3LFNXS
should be chosen.
Angle of Inclination
of the Tripping
Characteristic
The graph of the tripping characteristics is determined, among others, by the inclina-
tion angle 'LVWDQFH$QJOH (address ). Details about the tripping characteris-
tics can be found in Sub-section 2.2.2 and 2.2.3). Usually the line angle is set here i.e.
the same value as at address /LQH$QJOH (Sub-section 2.1.5.1). Irrespective
of the line angle it is, however, possible to select a different inclination angle of the trip-
ping characteristic.
Parallel Line Mea-
sured Value Correc-
tion (optional)
The mutual coupling between the two lines of a double-circuit configuration is only rel-
evant to the 7SA522 when it is applied on a double-circuit line and when it is intended
to implement parallel line compensation. A prerequisite is that the earth current of the
parallel line is connected to the I
4
measuring input of the device and this is entered in
the configuration settings. In this case, the setting 3DUDO/LQH&RPS = <(6 must be
made at address (default setting).
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