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 indication “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 reclosure 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.
This automatic blocking function requires the condition of the system to be detected without doubt. This
means that it is only active if all three current and voltage transformers are connected.
According to
the device calculates the voltage to be monitored:
3·U
0
= U
L1
+ U
L2
+ U
L3
.
This applies if no suitable voltage is connected to the fourth measuring input U
4
.
However, if the displacement voltage U
delta
of the voltage transformer set is directly connected to the fourth
measuring input U
4
of the device and this information was entered during configuration, the device will auto-
matically use this voltage and calculate the triple zero-sequence voltage.
3·U
0
=
Uph / Udelta
·U
4
Since the voltage transformation ratio of the voltage transformer set is usually
[spguebersetz-spgwdlr-wlk-310702, 1, en_GB]
the factor is set to
Uph / Udelta
= 3/√3 = √3 = 1.73. For more details, refer to Power System Data 1 at
margin heading “Voltage Connections” via address 211.
Functions
2.5 Under and over-voltage protection (optional)
SIPROTEC 4, 7VK61, Manual
101
C53000-G1176-C159-5, Edition 05.2018
Summary of Contents for SIPROTEC 4 7VK61
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