Siemens SIPROTEC 7SD610 Manual page 156

Functions
2.11 Undervoltage and Overvoltage Protection (optional)
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.
Compounding is only available if address 137 is set to Enabl. w. comp.. In this case the calculated voltage
at the other line end is also indicated in the operational measured values.
Note
Compounding is not suited for lines with series capacitors.
The voltage at the remote line end is calculated from the voltage measured at the local line end and the flowing
current by means of a PI equivalent circuit diagram (refer also to Figure 2-58).
with
U
End
U
Meas
I
Meas
C
L
R
L
L
L
Figure 2-58
156
with configurable compounding
1
the calculated voltage at the remote line end,
the measured voltage at the local line end,
the measured current at the local line end,
the line capacitance,
the line resistance,
the line inductance.
PI equivalent diagram for compounding
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011