Siemens SIPROTEC 7SJ61 Manual page 68

Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
User-defined Characteristics (phases and ground)
Having set address 112 Charac. Phase or 113 = Charac. Ground = User Defined PU or User def.
Reset when configuring the protective functions (Section 2.1.1.2), the user-defined curves will also be avail-
able. A maximum of 20 value pairs (current and time) may be entered at address 1230 51/51N or 1330
50N/51N in this case. This option allows point-by-point entry of any desired curve. When setting address 112
= User def. Reset or 113 = User def. Reset additional value pairs (current and reset time) may be
entered in address 1231 MofPU Res
Since current values are rounded in a specific pattern before they are processed in the device (see Table 2-3),
we recommend to use exactly the same preferred current values you can find in this table.
The current and time value pairs are entered as multiples of addresses 1207 51 PICKUP and 1208 51 TIME
DIAL for the phase currents and 1307 and 1308 for the ground system. Therefore, it is recommended that
these addresses are initially set to 1.00 for simplicity. Once the curve is entered, the values at addresses 1207
or1307 or/and 1208 or 1308 can be modified later to allow moving the curve in a different direction.
The default setting of current values is ∞. They are, therefore, disabled and no pickup or tripping of these pro-
tection functions will occur.
The following must be observed:
• The value pairs should be entered in increasing sequence. If desired, fewer than 20 pairs can be entered.
In most cases, about 10 pairs is sufficient to define the characteristic accurately. A value pair which is not
used has to be made invalid by entering "∞" for the threshold! The user must ensure that the value pairs
produce a clear and constant characteristic .
The current values entered should be those from the following table, along with the matching times. Deviat-
ing values MofPU (multiples of PU-values) are rounded. This, however, will not be indicated.
Currents smaller than the current value of the smallest curve point will not lead to an extension of the tripping
time. The pickup curve (see Figure 2-14, right side) runs parallel to the current axis, up to the smallest
current value point.
Currents larger than the largest current value entered will not lead to a reduction of the tripping time. The
pickup curve (see Figure 2-14, right side) runs parallel to the current axis, beginning with the greatest current
value point.
Table 2-3
MofPU = 1 to 1.94
1.00
1.06
1.13
1.19
1.25
1.31
1.38
1.44
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Preferential values of standardized currents for user-defined tripping curves
MofPU = 2 to 4.75
1.50 2.00
1.56 2.25
1.63 2.50
1.69 2.75
1.75 3.00
1.81 3.25
1.88
1.94
T/Tp or 1331 MofPU Res T/TEp to represent the dropout curve.
MofPU = 5 to 7.75
3.50 5.00
3.75 5.25
4.00 5.50
4.25 5.75
4.50 6.00
4.75 6.25
MofPU = 8 to 20
6.50 8.00
6.75 9.00
7.00 10.00
7.25 11.00
7.50 12.00
7.75 13.00
14.00
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
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