2 Functions
154
7SD610 Manual
C53000-G1176-C145-4
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 2-55).
with
U
End
the calculated voltage at the remote line end,
U
Meas
the measured voltage at the local line end,
I
Meas
the measured current at the local line end,
C
L
the service capacitance of the line,
R
L
the ohmic service resistance of the line,
L
L
the line inductance.
Figure 2-55 PI equivalent diagram for compounding
Overvoltage nega-
tive sequence
system U
2
The device calculates the negative sequence system voltages according to its defining
equation:
U
2
=
1
/
3
·(U
L1
+ a
2
·U
L2
+ a·U
L3
)
where a
= e
j120°
.
The resulting negative sequence voltage is fed to the two threshold stages U2> and
U2>>. Figure 2-56 shows the logic diagram. By combining the associated time delays
T U2> and T U2>> a two-stage overvoltage protection for the negative sequence
system is formed. Here too, the drop-out to pickup ratio can be set.
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