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 earthed
networks: a high value of voltage 3U
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 earthed networks:
a high value of voltage 3U
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.
7.2.3
Setting guidelines
IP15000-1 v1
7.2.3.1
General
M13683-3 v5
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 (
UBase
) 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.
7.2.3.2
Setting of common parameters
M13683-9 v9
Set the operation mode selector
Operation
to
On
to release the fuse failure
function.
The voltage threshold
USealIn<
is used to identify low voltage condition in the
system. Set
USealIn<
below the minimum operating voltage that might occur
during emergency conditions. We propose a setting of approximately 70% of
UBase
.
The drop off time of 200 ms for dead phase detection makes it recommended to
always set
SealIn
to
On
since this will secure a fuse failure indication at persistent
1MRK 511 423-UEN A
Section 7
Secondary system supervision
Bay control REC650 2.2 IEC
91
Application manual
