Table of Contents
Advertisement
Figure 2-23
Logic diagram of the overvoltage protection for the negative sequence voltage system U
The overvoltage protection for the negative sequence system can also be blocked via a binary input „>U2>(>)
BLK". The stages of the negative sequence voltage protection are automatically blocked as soon as an asym-
metrical voltage failure was detected („Fuse–Failure–Monitor", also see Section 2.7.1, margin heading „Fuse
Failure Monitor (Non-symmetrical Voltages))" or when the trip of the mcb for voltage transformers has been
signalled via the binary input „>FAIL:Feeder VT" (internal indication „internal blocking").
During single-pole dead time the stages of the negative sequence overvoltage protection are automatically
blocked since arising negative sequence values are only influenced by the asymmetrical power flow, not by the
fault in the system. 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
negative sequence system must be blocked via a binary input during single-pole tripping.
Single-Phase Voltage Connection
Please bear in mind that the device is designed for a three-phase voltage connection. Single-phase connection
is also possible but no adjustments have been made in this respect. This must be taken into consideration when
setting the pickup value.
Overvoltage zero sequence system 3U
Figure 2-24 depicts the logic diagram of the zero sequence voltage stage. The fundamental frequency is nu-
merically filtered from the measuring voltage so that the harmonics or transient voltage peaks remain largely
harmless.
The triple zero sequence voltage 3·U
associated time delays T 3U0> and T 3U0>> these stages form a two-stage overvoltage protection for the
SIPROTEC, 7VK61, Manual
C53000-G1176-C159-3, Release date 05.2009
0
is fed to the two threshold stages 3U0> and 3U0>>. Combined with the
0
2.5 Under and over-voltage protection (optional)
2
Functions
99
Advertisement
Table of Contents
