Table of Contents
Advertisement
1
1.1
1.2
1.3
136
Fuse failure supervision (FUSE)
Fuse failure supervision (FUSE)
Application
The fuse failure supervision function, FUSE, continuously supervises the ac voltage circuits be-
tween the voltage instrument transformers and the terminal. Different output signals can be used
to block, in case of faults in the ac voltage secondary circuits, the operation of the distance pro-
tection and other voltage-dependent functions, such as the synchro-check function, undervoltage
protection, etc.
Different measurement principles are available for the fuse failure supervision function.
The FUSE function based on zero sequence measurement principle, is recommended in directly
or low impedance earthed systems.
Functionality
The FUSE function based on the zero sequence measurement principle continuously measures
the zero sequence current and voltage in all three phases. It operates if the measured zero se-
quence voltage increases over preset operating value, and if the measured zero sequence current
remains below the preset operating value.
Three output signals are available. The first depends directly on the voltage and current mea-
surement. The second depends on the operation of the dead line detection function, to prevent
unwanted operation of the distance protection if the line has been deenergised and energised un-
der fuse failure conditions. The third depends on the loss of all three measured voltages. A spe-
cial function input serves the connection to the auxiliary contact of a miniature circuit breaker,
MCB (if used), to secure correct operation of the function on simultaneous interruption of all
three measured phase voltages also when the additional delta current and delta voltage algorithm
is not present in the function block.
Function block
FUSE-
FUSE
BLOCK
VTSU
MCB
VTSZ
DISC
VTF3PH
DLCND
xx01000096.vsd
Figure 69:
Function block, zero sequence
Chapter 8
Secondary system supervision
Advertisement
Table of Contents
