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2 Functions
The overvoltage protection for the zero sequence system can also be blocked via a
binary input „>3U0>(>) BLK". The stages of the zero sequence voltage protection
are automatically blocked as soon as an asymmetrical voltage failure was detected
(„Fuse–Failure–Monitor", also see Section 2.15.1, margin heading „Fuse Failure
Monitor (Non-symmetrical Voltages))" or when the trip of the mcb for voltage trans-
formers has been signalled via the binary input „>FAIL:Feeder VT" (internal indi-
cation „internal blocking").
The stages of the zero sequence voltage protection are automatically blocked during
single-pole automatic reclose dead time to avoid pickup with the asymmetrical power
flow arising during this state. If the device cooperates with an external automatic re-
closure function, or if a single-pole tripping can be triggered by a different protection
system (working in parallel), the overvoltage protection for the zero sequence system
must be blocked via a binary input during single-pole tripping.
According to Figure 2-57 the device calculates the voltage to be monitored:
This applies if no suitable voltage is connected to the fourth measuring input U
However, if the displacement voltage U
connected to the fourth measuring input U
entered during configuration, the device will automatically use this voltage and calcu-
late the triple zero sequence voltage.
Since the voltage transformation ratio of the voltage transformer set is usually
the factor is set to Uph / Udelta = 3/√3 = √3 = 1.73. For more details, refer to
General Power System Data (Power System Data 1) in Section 2.1.4.1 at
margin heading „Voltage Connections" via address 211.
156
3·U
= U
+ U
+ U
.
0
L1
L2
L3
= Uph / Udelta ·U
3·U
0
of the voltage transformer set is directly
delta
of the device and this information was
4
4
.
4
7SD610 Manual
C53000-G1176-C145-4
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