Siemens SIPROTEC 7SD610 User Manual

Functions
2.11 Undervoltage and Overvoltage Protection (optional)
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
158
Overvoltage zero-sequence system 3U
0
Figure 2-60 depicts the logic diagram of the zero-sequence voltage stage. The fundamental component is nu-
merically filtered from the measuring voltage so that the harmonics or transient voltage peaks remain largely
eliminated.
The triple zero-sequence voltage 3·U
0
is fed to the two threshold stages 3U0> (address 3722) and 3U0>> (ad-
dress 3724). Combined with the associated time delays T 3U0> (address 3723) and T 3U0>> (address
3725), these stages form a two-stage overvoltage protection for the zero-sequence system. Here too, the drop-
out to pickup ratio can be set (3U0>(>) RESET, address 3729). Furthermore, a restraint delay can be config-
ured which is implemented by repeated measuring (approx. 3 periods).
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 asymmet-
rical 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 transformers has been sig-
nalled 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 co-
operates 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.
According to Figure 2-60 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
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.

Siemens SIPROTEC 7SD610 Specifications

General

Brand	Siemens
Model	SIPROTEC 7SD610
Category	Relays
Language	English