Siemens 7SC80 Manual page 92

Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
51N-1 Drop-out or 1341 51N-2 Drop-out or 1347 51N-3 Drop-out or 1353 51N-4 Drop-out,
resets will occur in accordance with the reset curves as described before. Recloser curves don't support disk
emulation.
The current values are set in address 1333 51N-1 PICKUP, Address 1339 51N-2 PICKUP, Address 1345
51N-3 PICKUP and Address 1351 51N-4 PICKUP. These pickup values could be set to ∞ individually. If an
inverse element's pickup value is set to ∞, this element is disabled. The setting is mainly determined by the
maximum anticipated operating current. Pickup due to overload should never occur since in this mode, the
device operates as fault protection with correspondingly short tripping times and not as overload protection.
The corresponding time multipliers are set at address 1334 51N-1 T DIAL, Address 1340 51N-2 T DIAL,
Address 1346 51N-3 T DIAL or Address 1352 51N-4 T DIAL. They must be coordinated with the time
coordination chart of the system.
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 protection functions (Section
also be available. 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 T/Tp or1331 MofPU Res T/TEp to represent the dropout curve.
Since current values are rounded in a specific pattern before they are processed in the device (see
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
or 1307 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
protection 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.
Deviating 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
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
greatest current value point.
Table 2-5
MofPU = 1 to 1.94
1.00 1.50
1.06 1.56
1.13 1.63
1.19 1.69
1.25 1.75
1.31 1.81
1.38 1.88
1.44 1.94
92
Figure
Figure 2-19, right side) runs parallel to the current axis, beginning with the
Preferential values of standardized currents for user-defined tripping curves
MofPU = 2 to 4.75
2.00 3.50
2.25 3.75
2.50 4.00
2.75 4.25
3.00 4.50
3.25 4.75
2.1.1.2 Setting Notes), user-defined curves will
2-19, right side) runs parallel to the current axis, up to the
MofPU = 5 to 7.75
5.00 6.50
5.25 6.75
5.50 7.00
5.75 7.25
6.00 7.50
6.25 7.75
E50417-G1140-C486-A8, Edition 07.2017
Table 2-5),
MofPU = 8 to 20
8.00 15.00
9.00 16.00
10.00 17.00
11.00 18.00
12.00 19.00
13.00 20.00
14.00
SIPROTEC Compact, 7SC80, Manual