Siemens SIPROTEC 4 User Manual page 78

Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
Table 2-5
.MofPU = 1 to 0.86
1.00 0.93
0.99 0.92
0.98 0.91
0.97 0.90
0.96 0.89
0.95 0.88
0.94 0.86
When using DIGSI to make settings, a dialog box opens where you can enter up to 20 value pairs (measured
quantity and trip time) (see
In order to represent the characteristic graphically, the user should click on "characteristic". The previously
entered characteristic will appear as shown in
The characteristic curve shown in the graph can be modified later on. Placing the mouse cursor over a point
on the characteristic, the cursor changes to the shape of a hand. Press and hold the left mouse button and
drag the data item to the desired position. Releasing the mouse button will automatically update the value in
the value table.
The respective upper limits of the ranges of value are indicated by dotted lines in the right-hand and upper
area of the system of coordinates. If the position of a data point lies outside these limits, the associated value
is set to infinity.
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Figure 2-19
Inrush Restraint
When applying the protection device to transformers where high inrush currents are to be expected, the
7SJ62/64 can make use of an inrush restraint function for the overcurrent elements 50-1, 51, 50N-1 and 51N.
Inrush restraint is only effective and accessible if address 122 InrushRestraint was set to Enabled. If this
function is not required, then Disabled is set. In address 2201 INRUSH REST., the function is switched ON
or OFF jointly for the overcurrent elements 50-1 PICKUP,51 PICKUP, 50N-1 PICKUP and 51N PICKUP
The inrush restraint is based on the evaluation of the 2nd harmonic present in the inrush current. Upon
delivery from the factory, a ratio Ι
be changed. The setting value is identical for all phases and ground. However, the component required for
restraint may be adjusted to system conditions in address 2202 2nd HARMONIC. To provide more restraint in
exceptional cases, where energizing conditions are particularly unfavorable, a smaller value can be set in the
aforementioned address, e.g. 12 %. Irrespective of parameter 2202 2nd HARMONIC, rush blocking will only
occur if the absolute value of the 2nd harmonic is at least 0.125 * INom,sec.
78
Preferential values of standardized currents for user-defined reset curves
MofPU = 0.84 to 0.67
0.84 0.75
0.83 0.73
0.81 0.72
0.80 0.70
0.78 0.69
0.77 0.67
Figure 2-19).
Entry and visualization of a user-defined tripping characteristic in DIGSI — example
/Ι of 15 % is set. Under normal circumstances, this setting will not need to
2f f
MofPU = 0.66 to 0.38
0.66 0.53
0.64 0.50
0.63 0.47
0.61 0.44
0.59 0.41
0.56 0.38
Figure 2-19.
MofPU = 0.34 to 0.00
0.34 0.16
0.31 0.13
0.28 0.09
0.25 0.06
0.22 0.03
0.19 0.00
SIPROTEC 4, 7SJ62/64, Manual
C53000-G1140-C207-8, Edition 08.2016