Siemens 7SC80 Manual page 88

Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
•
Measurement with instantaneous values
This procedure compares the instantaneous values to the set threshold. The element picks up at 2 · 2 ·
setting value (rms). It does not perform a mean-value calculation and is thus sensitive with regard to
disturbances. This measurement method should only be selected if an especially short pickup time of the
element is required. In this measurement procedure, the operating time of the element is reduced
compared to the measurement of effective values or fundamental harmonics (see "Technical Data").
The type of the comparison values can be set under the following addresses:
50-3 element
50-2 element
50-1 element
51 element
51-1 element
51-2 element
51-3 element
51-4 element
50N-3 element
50N-2 element
50N-1 element
51N element
51N-1 element
51N-2 element
51N-3 element
51N-4 element
High-Set Current Elements 50-2, 50-3 (Phases)
The pickup currents of the high-current elements 50-2 PICKUP or 50-3 PICKUP are set at address 1202
and 1217. The corresponding time delay 50-2 DELAY or 50-3 DELAY can be configured at address 1203 or
1218. It is usually used for current grading for large impedances as occur in transformers. The time delay is set
to pick up on short circuits up to this impedance.
Example of the high-set current element 50-2 PICKUP: Transformer used for busbar supply with the
following data:
Rated apparent power
Transformer impedance
Primary nominal voltage
Secondary nominal voltage
Vector groups
Neutral point
Fault power on 110 kV-side
Based on the data above, the following fault currents are calculated:
Three-Phase High Voltage Side Fault Current
Three-Phase Low Voltage Side Fault Current
On the High Voltage Side Flowing
The nominal current of the transformer is:
= 84 A (High Voltage Side)
Ι
NomT, 110
Current Transformer (High Voltage Side)
Current Transformer (Low Voltage Side)
88
Address 1219 50-3 measurem.
Address 1220 50-2 measurem.
Address 1221 50-1 measurem.
Address 1222 51 measurem.
Address 1232 51-1 measurem.
Address 1244 51-2 measurem.
Address 1258 51-3 measurem.
Address 1266 51-4 measurem.
Address 1319 50N-3 measurem.
Address 1320 50N-2 measurem.
Address 1321 50N-1 measurem.
Address 1322 51N measurem.
Address 1332 51N-1 measure.
Address 1338 51N-2 measure.
Address 1344 51N-3 measure.
Address 1350 51N-4 measure.
S = 16 MVA
NomT
ZT = 10 %
V = 110 kV
Nom1
V = 20 kV
Nom2
Dy 5
Grounded
1 GVA
at 110 kV = 5250 A
at 20 kV = 3928 A
at 110 kV = 714 A
= 462 A (Low Voltage
Ι
NomT, 20
Side)
100 A/1 A
500 A/1 A
E50417-G1140-C486-A8, Edition 07.2017
SIPROTEC Compact, 7SC80, Manual