protection and monitoring devices are another possibilities. These solutions are combined
to get the best possible effect in the fuse failure supervision function (FUFSPVC).
FUFSPVC function built into the IED products can operate on the basis of external binary
signals from the miniature circuit breaker or from the line disconnector. The first case
influences the operation of all voltage-dependent functions while the second one does not
affect the impedance measuring functions.
The negative sequence detection algorithm, based on the negative-sequence measuring
quantities is recommended for use in isolated or high-impedance grounded networks: a
high value of voltage 3V
2
without the presence of the negative-sequence current 3I
2
is a
condition that is related to a fuse failure event.
The zero sequence detection algorithm, based on the zero sequence measuring quantities
is recommended for use in directly or low impedance grounded networks: a high value of
voltage 3V
0
without the presence of the residual current 3I
0
is a condition that is related
to a fuse failure event. In cases where the line can have a weak-infeed of zero sequence
current this function shall be avoided.
A criterion based on delta current and delta voltage measurements can be added to the fuse
failure supervision function in order to detect a three phase fuse failure. This is beneficial
for example during three phase transformer switching.
14.2.3 Setting guidelines
14.2.3.1 General
The negative and zero sequence voltages and currents always exist due to different non-
symmetries in the primary system and differences in the current and voltage instrument
transformers. The minimum value for the operation of the current and voltage measuring
elements must always be set with a safety margin of 10 to 20%, depending on the system
operating conditions.
Pay special attention to the dissymmetry of the measuring quantities when the function is
used on long untransposed lines, on multicircuit lines and so on.
The settings of negative sequence, zero sequence and delta algorithm are in percent of the
base voltage and base current for the function. Common base IED values for primary
current (IBase), primary voltage (VBase) and primary power (SBase) are set in Global
Base Values GBASVAL. The setting GlobalBaseSel is used to select a particular
GBASVAL and used its base values.
14.2.3.2 Setting of common parameters
Set the operation mode selector Operation to Enabled to release the fuse failure function.
1MRK 506 369-UUS - Section 14
Secondary system supervision
Line distance protection REL670 2.2 ANSI 625
Application manual
To Next Page
Loading...
