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The table gives an overview of the functions that can be activated for the corresponding connection type (de-
pends also on the ordering number). The functions which are not shown are available for all connection types.
Connection type
Directional definite-time/inverse-time
Van, Vbn, Vcn
Vab, Vbc, VGnd
Vab, Vbc
Vab, Vbc, Vx
1)
Determination of the direction is only possible by evaluating the negative sequence system (otherwise select
zero sequence system or negative sequence system).
Measured values, which due to the chosen voltage connection cannot be calculated, will be displayed as dots.
With capacitive voltage connection, some functions are not available. Table 2-1 gives information on this topic.
The Appendix provides some connection examples for all connection types at A.3.
Capacitive Voltage Measurement
When selecting capacitive voltage measurement in the Device Configuration at address 192 Cap.
Volt.Meas., the voltage will be measured via so-called bushing capacitances. The usual primary voltage
transformers are not relevant in this case. Capacitive voltage measurement always measures the phase-to-
Ground voltages from the protection device. The following figure shows this type of connection.
Figure 2-4
In addition to the bushing capacitances, the line and stray capacitances too affect the measured voltage fed to
the protection device. These capacitances are primarily determined by the type and length of the connection
line.
The voltage inputs of the device feature an input capacitance of 2.2nF and an ohmic component of 2.0 MΩ.
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
overcurrent protection ground
yes
yes
1)
yes
1)
yes
Connection for a capacitive voltage measurement in principle
Functions
Sensitive ground fault detection
yes
yes
no
no
Functions
2.1 General
Directional intermittent
ground fault
yes
yes
no
no
43
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