Siemens siprotec 7SA6 User Manual page 390

Functions
U
L1-E
U
L2-E
U
L3-E
L1
L2
L3
FNo 10201
>Uph-e>(>) BLK
Figure 6-105 Logic diagram of the overvoltage protection for phase voltages
Overvoltage
Phase–Phase
Overvoltage
Positive Sequence
System U
1
6-208
"&! Vƒu²r3
"&( Vƒu²r33ÃS@T@U
U>
U>>
"&# Vƒu²r33
The phase–phase overvoltage protection operates just like the phase–earth
protection except that it detects phase–to–phase voltages. Accordingly, phase–to–
phase voltages which have exceeded one of the stage thresholds 8SKSK! or 8SK
SK!! are also indicated. Otherwise, Figure 6-105 also applies in principle.
The phase–phase overvoltage protection can also be blocked via a binary input
"!8SKSK! ! %/.".
The device calculates the positive sequence system voltage according to its defining
equation:
⋅(U
1
U = / + a⋅U
1 3 L1 L2
j120°
with a = e .
The resulting single–phase AC voltage is fed to the two threshold stages 8! and
8!! (see Figure 6-106). Combined with the associated time delays these stages
form a two-stage overvoltage protection for the positive sequence system. Here too,
the drop-off to pick-up ratio can be set.
The overvoltage protection for the positive sequence system can also be blocked via
a binary input "!8! ! %/.".
≥1
T
≥1
UÃVƒu²r3 "&"
UÃVƒu²r33 "&$
≥1 T
⋅U
2
+ a )
L3
FNo 10242 to 10244
Uph-e>(>) PU L1
Uph-e>(>) PU L2
Uph-e>(>) PU L3
FNo 10240
Uph-e> Pickup
FNo 10245
0
T Uph-e> TimeOut
FNo 10247
≥1
Uph-e>(>) TRIP
FNo 10246
0
T Uph-e>> TimeOut
FNo 10241
Uph-e>> Pickup
C53000-G1176-C133-1
J
7SA6 Manual