Siemens SIPROTEC 7SD610 Manual page 215

Broken wire monitoring
The broken wire monitoring is enabled or disabled via the parameter 2931 BROKEN WIRE. The differential pro-
tection function is only blocked with the setting ON. By means of the setting Alarm only, a broken wire can
be signalled; the protection functions are not blocked.
In case of a 1-1/2 circuit breaker arrangement, the parameter 208 1-1/2 CB is to be set to YES. Parameter
2935 ΔI min indicates the minimum difference for this circuit breaker arrangement by which the current would
decrease in case of a wire break.
Asymmetrical measuring voltage failure "Fuse Failure Monitor"
The settings for the „fuse failure monitor" for non-symmetrical measuring voltage failure must be selected such
that on the one hand it is reliably activated if a phase voltage fails (address 2911 FFM U>(min)), but does not
pick up on earth faults in an earthed network on the other hand. Accordingly, address 2912 FFM I< (max)
must be set sufficiently sensitive (below the smallest fault current during earth faults). This setting is only pos-
sible in DIGSI at Display Additional Settings.
In address 2910 FUSE FAIL MON., the „Fuse Failure Monitor", e.g. during asymmetrical testing, can be
switched OFF.
Three-phase measuring voltage failure "Fuse Failure Monitor"
The minimal voltage below which a three-phase measured voltage failure is detected, is set in address 2913
FFM U<max (3ph), unless a current step takes place simultaneously which exceeds the limit according to
address 2914 FFM Idelta (3p). These settings can only be changed via DIGSI at Display Additional Set-
tings.
In address 2910 FUSE FAIL MON., the „Fuse Failure Monitor", e.g. during asymmetrical testing, can be
switched OFF.
Measured voltage failure monitoring
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 in DIGSI at Display Additional Settings.
Circuit breaker for voltage transformers
If a circuit breaker for voltage transformers (VT mcb) is installed in the secondary circuit of the voltage trans-
formers, the status is sent, via binary input, to the device informing it about the position of the VT mcb. If a short-
circuit in the secondary circuit initiates the tripping of the VT mcb, the voltage protection function is blocked, as
otherwise it would cause spurious tripping as a result of the absent measured voltage. The reaction time is set
at address 2921 T mcb.
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
Functions
2.15 Monitoring Functions
215