Functions
2.14 Monitoring Functions
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
176
2.14.1.5 Setting Notes
General
The sensitivity of measured value monitoring can be modified. Default values which are sufficient in most cases
are preset. If especially high operational asymmetries of the currents and/or voltages are anticipated during
operation, or if it becomes apparent during operation that certain monitoring functions pick up sporadically, then
the setting should be less sensitive.
The measurement supervision can be switched ON or OFF in address 2901 MEASURE. SUPERV.
Symmetry Monitoring
Address 2902 BALANCE V-LIMIT determines the limit voltage (phase-to-phase), above which the voltage
symmetry monitor is effective. Address 2903 BAL. FACTOR V is the associated symmetry factor; that is, the
slope of the symmetry characteristic curve. The indication „Fail V balance“ (no. 167) can be delayed at
address 2908 T BAL. V LIMIT. These settings can only be changed via DIGSI at Display 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 associated symmetry factor; that is, the slope of the symmetry
characteristic curve. The indication „Fail I balance“ (no. 163) can be delayed at address 2909 T BAL.
I LIMIT. These settings can only be changed via DIGSI at Display Additional Settings.
Summation Monitoring
Address 2906 Σ I THRESHOLD determines the limit current, above which the current sum monitor is activated
(absolute portion, only relative to I
Nom
). The relative portion (relative to the maximum conductor current) for ac-
tivating the current sum monitor is set at address 2907 Σ I FACTOR. These settings can only be changed via
DIGSI at Display Additional Settings.
Note
Current sum monitoring can operate properly only when the ground current of the protected line is fed to the
fourth current measuring input (I
4
) of the device. The I
4
transformer must have been configured as In prot.
line via parameter I4 transformer (220), see Appendix at A.3.
Wire Break Monitoring
Wire break monitoring is enabled or disabled via parameter 2931 BROKEN WIRE. Only when set to ON, is the
differential protection function blocked. When set to Alarm only, a broken wire is signaled but the protection
functions are not blocked.
Asymmetrical Measuring Voltage Failure "Fuse Failure Monitor"
The settings for the „fuse failure monitor“ for non-symmetrical measuring voltage failure (address 2911 FFM
V>(min)) are to be selected so that reliable activation occurs if a phase voltage fails, but not such that false
activation occurs during ground faults in a grounded network. Address 2912 FFM I< (max) must be set as
sensitive as required (with ground faults, below the smallest fault current). These settings can only be changed
via DIGSI at Display Additional Settings.
In address 2910 FUSE FAIL MON., the „fuse failure monitor“ can be switched OFF e.g. during asymmetrical
testing.
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