Table of Contents
Advertisement
Functions
2.24 Monitoring Functions
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"
In address 2913 FFM U<max (3ph) the minimum voltage threshold is set. If the measured 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 settings can only be changed via DIGSI at Display Ad-
ditional Settings.
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 voltage transformer circuit breaker is installed in the secondary circuit of the voltage transformers, its status
is to be sent to the device via binary input. If a short circuit in the secondary circuit trips the VT circuit breaker,
the distance protection must be blocked immediately, since it would otherwise trip spuriously due to the missing
measuring voltage while load current is flowing. This blocking must be faster than the first stage of the distance
protection. This requires an extremely short response time of the VT circuit breaker (≤ 4 ms at 50 Hz nominal
frequency). If the auxiliary contact of the mcb fails to meet this requirement, the response time must be set at
address 2921 T mcb. This, however, will delay the response of the protection function.
436
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
Advertisement
Table of Contents
