Siemens SIPROTEC 7SD610 Manual page 101

The current phase earth voltage is used
• for single-pole or three-pole faults,
• if phase-earth voltage > 4V
• not within the first 50 ms after short-circuit, as the current voltage is then disturbed by transients.
The saved phase-earth voltage is used
• for single-pole or three-pole faults,
• up to a maximum of 2 s after saving the phasors
• if there was no triggering or single-pole pause prior to the short-circuit.
The unfaulted current phase-earth voltage is used
• for single-pole faults
• for undisturbed unfaulted phase-earth voltages
• if the voltage level is > 70% of the rated voltage.
The negative sequence systems U
• for single-pole or two-pole faults
• ifI > 50 mA and U
2
If the negative sequence systems are used in the case of two single-pole short-circuits, the most powerful short
circuit is valid for direction determination.
The current voltage is used if it is > 5V.
If none of the previously measuring values is available, an already existing result of the direction determination
is used, or the directional stage is blocked for the respective phase.
For the directional 3I0> stages, the measuring voltage used is determined by the parameter 2603 Direct.
3I0.
• If with U0/I0 has been set, the current zero sequence values 3U
voltage is too small for a direction measurement, the directional 3I0>stages are blocked.
• If with U2/I2 has been set, the current negative sequence values 3U
sequence voltage is too small for a direction measurement, the directional 3I0>stages are blocked.
• If U0/I0 or U2/I0 has been set, negative sequence or zero sequence values can be used. Negative se-
quence system values are used if they are larger then the respective zero sequence system values. If the
measuring variables of both systems are unavailable, the directional 3I0> stages are blocked.
Note
During a measuring voltage failure, all directional stages are blocked.
During the single-pole dead time, all earth current stages are blocked.
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
and I are used
2 2
> 5V.
2
2.9 Backup Time Overcurrent Protection
and 3I are used. If the zero sequence
0 0
and 3I are used. If the negative
2 2
Functions
101