Siemens SIPROTEC Manual page 363

Overvoltage positive sequence system U
The device calculates the positive sequence system according to its defining equation
1
U = / ·(U
1 3 L1
j120°
where a = e
The resulting positive sequence voltage is fed to the two threshold stages U1> (address 3732) and U1>> (ad-
dress 3734) (see Figure 2-173). Combined with the associated time delays T U1> (address 3733) and T U1>>
(address 3735), these stages form a two-stage overvoltage protection based on the positive sequence system.
Here too, the drop-out to pickup ratio can be set.
The overvoltage protection for the positive sequence system can also be blocked via a binary input „>U1>(>)
BLK".
Figure 2-173 Logic diagram of the overvoltage protection for the positive sequence voltage system
Overvoltage protection U
The overvoltage protection for the positive sequence system may optionally operate with compounding. The
compounding calculates the positive sequence system of the voltage at the remote line end. This option is thus
particularly well suited for detecting a steady-state voltage increase caused by long transmission lines operat-
ing at weak load or no load due to the capacitance per unit length (Ferranti effect). In this case the overvoltage
condition exists at the other line end but it can only be removed by switching off the local line end.
For calculating the voltage at the opposite line end, the device requires the line data (inductance per unit length,
capacitance per unit length, line angle, line length) which were entered in the Power System Data 2 (Section
2.1.4.1) during configuration.
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
1
2
+ a·U + a ·U )
L2 L3
.
with configurable compounding
1
2.19 Undervoltage and Overvoltage Protection (optional)
Functions
363