Siemens siprotec 7SA6 User Manual page 394

Functions
8VSSTVQÃVƒur1
"&$'
PI
„1"
PAA
I–REST> L1
I–REST> L2
I–REST> L3
U
L1-E
U
L2-E
U
L3-E
L1
L2
FNo 10206
>Uph-e<(<) BLK
Figure 6-108 Logic diagram of the undervoltage protection for phase voltages
Undervoltage
Phase–Phase
Undervoltage
Positive Sequence
System U
1
6-212
"&$! Vƒu²r1
≥1
&
U<
&
U<<
L3
"&$# Vƒu²r11
Basically, the phase–phase undervoltage protection operates like the phase–earth
protection except that it detects phase–to–phase voltages. Accordingly, both phases
are indicated during pick-up of an undervoltage stage if one of the stage thresholds
8SKSK or 8SKSK was undershot. Beyond this, Figure 6-108 applies in
principle.
It is sufficient for the current criterion that current flow is detected in one of the involved
phases.
The undervoltage protection phase–phase can also be blocked via a binary input
"!8SKSK %/.". There is an automatic blocking if the measuring voltage failure
was detected or voltage mcb tripping was indicated (internal blocking of the phases
affected by the voltage failure).
During single-pole dead time for automatic reclosure (using the internal automatic
reclosure function) the stages of the undervoltage protection are automatically
blocked in the disconnected phase so that it does not respond to the undervoltage of
the disconnected phase provided that the voltage transformers are located on the
outgoing side.
The device calculates the positive sequence system according to its defining equation
⋅(U
1
U = / + a⋅U
1 3 L1 L2
j120°
with a = e .
≥1
≥1
UÃVƒu²r1
UÃVƒu²r11
≥1
⋅U
2
+ a )
L3
FNo 10312 to 10314
Uph-e<(<) PU L1
Uph-e<(<) PU L2
Uph-e<(<) PU L3
FNo 10310
Uph-e< Pickup
FNo 10315
T 0
T Uph-e< TimeOut
"&$"
FNo 10317
≥1
Uph<(<) TRIP
"&$$
FNo 10316
T 0
T Uph-e<<TimeOut
FNo 10311
Uph-e<< Pickup
C53000-G1176-C133-1
7SA6 Manual