Siemens SIPROTEC 4, User Manual

Page: 103 / 734

If the relay is used to protect transformers or motors with large inrush currents, the inrush restraint feature of
7SJ62/64 may be used for the 67N-TOC element (
67N-TOC PICKUP
) (for more information see margin
heading "Inrush Restraint").
If the inverse time trip characteristic is selected, it must be noted that a safety factor of about 1.1 has already
been included between the pickup value and the setting value
67N-TOC PICKUP
. This means that a pickup
will only occur if a current of about 1.1 times the setting value is present. If
Disk Emulation
was selected at
address 1610
67N-TOC DropOut
, reset will occur in accordance with the reset curve as for the existing
nondirectional time overcurrent protection described in Section 2.2 Overcurrent Protection 50, 51, 50N, 51N .
The current value is set at address 1607
67N-TOC PICKUP
. The minimum appearing ground fault current is
most relevant for this setting.
The corresponding element time multiplication factor for an IEC characteristic is set at address 1608
67N-TOC
T-DIAL
and in address 1609
67N-TOC T-DIAL
for an ANSI characteristic. This has to be coordinated with
the system grading coordination chart for directional tripping. For ground currents with grounded network,
you can mostly set up a separate grading coordination chart with shorter delay times.
The time multiplier can also be set to ∞. After pickup the element will then not trip. Pickup, however, will be
signaled. If the 67N-TOC element is not required at all, address 116
67N/67N-TOC
should be set to
Defi-
nite Time
during protection function configuration (see Section 2.1.1).
User-defined characteristic (Inverse Time Phases and ground)
If address 115 or 116 were set to
User Defined PU
or
User def. Reset
during configuration of the
userdefined characteristic option, a maximum of 20 value pairs (current and time) may be entered at address
1530
67
or 1630
M.of PU TD
. This option allows point-by-point entry of any desired curve.
If address 115 or 116 were set to
User def. Reset
during configuration, additional value pairs (current
and reset time) may be entered in address 1531
MofPU Res T/Tp
or 1631
I/IEp Rf T/TEp
to represent
the reset curve.
Entry of the value pair (current and time) is a multiple of the settings of the values of the addresses 1507
67-
TOC PICKUP
or 1607
67N-TOC PICKUP
and 1508
67 TIME DIAL
or 1608
67N-TOC T-DIAL
. Therefore,
it is recommended that parameter values are initially set to 1.00 for simplicity. Once the curve is entered, the
settings at addresses 1507 and 1607 or/and 1508 and 1608 may be modified later on if necessary.
The default setting of current values is ∞. They are, therefore, not enabled — and no pickup or tripping of
these protective functions will occur.
The following must be observed:
•
The value pairs should be entered in increasing sequence. If desired, fewer than 20 pairs may be entered.
In most cases, about 10 pairs is sufficient to define the characteristic accurately. A value pair which will
not be used has to be made invalid entering ∞ for the threshold! The user must ensure the value pairs
produce a clear and constant characteristic.
The current values entered should be those from following Table, along with the matching times. Devi-
ating values MofPU (multiples of PU value) are rounded. This, however, will not be indicated.
Current flows less than the smallest current value entered will not lead to an extension of the tripping
time. The pickup curve (see
Figure 2-18 , right side) goes parallel to the current axis, up to the smallest
current point.
Current flows greater than the highest current value entered will not lead to a reduction of the tripping
time. The pickup characteristic (see
Figure 2-18 , right side) goes parallel to the current axis, beginning
with the greatest current point.
Table 2-9 Preferential values of standardized currents for user-defined tripping curves
MofPU = 1 bis 1.94 MofPU = 2 bis 4.75 MofPU = 5 bis 7.75 MofPU = 8 bis 20
1.00 1.50 2.00 3.50 5.00 6.50 8.00 15.00
1.06 1.56 2.25 3.75 5.25 6.75 9.00 16.00
1.13 1.63 2.50 4.00 5.50 7.00 10.00 17.00
1.19 1.69 2.75 4.25 5.75 7.25 11.00 18.00
1.25 1.75 3.00 4.50 6.00 7.50 12.00 19.00
Functions
2.3 Directional Overcurrent Protection 67, 67N
SIPROTEC 4, 7SJ62/64, Manual 103
C53000-G1140-C207-8, Edition 08.2016