2.22 Monitoring Functions
389
7SD5 Manual
C53000-G1176-C169-1
Symmetry
Monitoring
Address 2902 BALANCE U-LIMIT determines the limit voltage (phase-to-phase),
above which the voltage symmetry monitor is effective. Address 2903 BAL. FACTOR
U is the associated symmetry factor; that is, the slope of the symmetry characteristic
curve. The alarm „Fail U balance“ (No. 167) can be delayed in address 2908 T
BAL. U LIMIT. These settings can only be changed via DIGSI
®
at Additional Set-
tings.
Address 2904 BALANCE I LIMIT determines the limit current, above which the
current symmetry monitor is effective. Address 2905 BAL. FACTOR I is the associ-
ated symmetry factor; that is, the slope of the symmetry characteristic curve. The
alarm „Fail I balance“ (No. 163) can be delayed in address 2909 T BAL. I
LIMIT. These settings can only be changed via DIGSI
®
at Additional Settings.
Summation
Monitoring
Address 2906 ΣI THRESHOLD determines the limit current, above which the current
sum monitor is activated (absolute portion, only relative to I
N
). The relative portion (rel-
ative to the maximum conductor current) for activating the current sum monitor is set
at address 2907 ΣI FACTOR. These settings can only be changed via DIGSI
®
at Ad-
ditional Settings.
Note
Current sum monitoring can operate properly only when the residual current of the
protected line is fed to the fourth current input (II
4
) of the relay. The I
4
transformer must
have been configured as In prot. line via parameter I4 transformer (220).
Also, the fourth current input must have the ratings of a normal I
4
transformer. With a
sensitive transformer type, current sum monitoring is not activated.
Asymmetrical Mea-
suring Voltage
"Failure Fuse
F a i l u r e M o n i t o r "
The settings of the „fuse failure monitor“ for asymmetrical measured voltage failure
must be selected such that on the other hand reliable pickup of the monitoring is
ensured in the case of loss of a single-phase voltage (address 2911 FFM U>(min)),
while on the other hand a pickup due to earth faults in an earthed system is avoided.
In accordance with this requirement, address 2912 FFM I< (max) must be set suf-
ficiently sensitive (below the smallest fault current due to earth faults). These settings
can only be changed via DIGSI
®
at Additional Settings.
In address 2910 FUSE FAIL MON., the „fuse failure monitor“ can be switched OFF,
e.g. during asymmetrical testing.
Three-Phase Mea-
suring Voltage
Failure "Fuse
Failure Monitor"
In address 2913 FFM U<max (3ph) the minimum voltage threshold is set. If the mea-
sured voltage drops below this threshold and a simultaneous current jump which
exceeds the limits according to address 2914 FFM Idelta (3p) is not detected
while all three phase currents are greater than the minimum current required for the
impedance measurement by the distance protection according to address 1502
Minimum Iph>, a three-phase measured voltage failure is recognized. These set-
tings can only be changed via DIGSI
®
at Additional Settings.
In address 2910 FUSE FAIL MON., the „fuse failure monitor“ can be switched OFF,
e.g. during asymmetrical testing.
Measured Voltage
Failure Supervision
In address 2915 V-Supervision, the measured voltage supervision can be
switched to w/ CURR.SUP, w/ I> & CBaux or OFF. Address 2916 T V-
Supervision is used to set the waiting time of the voltage failure supervision. This
setting can only be changed via DIGSI
®
at Additional Settings.
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