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Mounting and Commissioning
3.2 Checking Connections
• If the voltage measurement is carried out via feedthrough capacitances, the feedthrough capacitance for the
7SK80 must be available exclusively.. Parallel connections such as, for example, CAPDIS are not permis-
sible.
In the case of a voltage measurement via feedthrough capacitances, the value of the individual capacitances
C1 and C2 for the three phases must be known approximately (also see Section 2.1.3.2,„ Capacitive Voltage
Measurement"). These capacitance values are configured via the parameter addresses 241
Volt.trans.A:C1 to 246 Volt.trans.C:C2 in the Power System Data 1. The value for the
feedthrough capacitances (C1) is usually in the range from 5 pF to 10 pF. The values for the line capacitanc-
es (C2) - also including the stray capacitance - basically depend on the cable type used and the cable length
for the measuring voltage connection. When entering the parameter for C2, the value of the capacitance of
the voltage input has to be added. This input capacitance can be estimated as 2200 pF. Inexactly configured
capacitance values will result in deviations during the measurement of the voltage amplitude and the voltage
phase angle.
If the phase-selective voltages on the primary side are known (usually the nominal voltage of the system
divided by √3), the values for the capacitances C1 can be optimized afterwards. The configured values of
C2 can also be optimized if the phase angles between the phase-to-ground voltages and the phase currents
are know. An explanation of the procedure for optimizing the input capacitances is to be found in Section
2.1.3.2,„Capacitive Voltage Measurement".
• If test switches are used for the secondary testing of the device, their functions must also be checked, in
particular that in the „Check" position the current transformer secondary lines are automatically short-circuit-
ed.
• Connect an ammeter in the supply circuit of the power supply. A range of about 2.5 A to 5 A for the meter is
appropriate.
• Switch on m.c.b. for auxiliary voltage (supply protection), check the voltage level and, if applicable, the po-
larity of the voltage at the device terminals or at the connection modules.
• The current input should correspond to the power input in neutral position of the device. The measured
steady state current should be insignificant. Transient movement of the ammeter merely indicates the charg-
ing current of capacitors.
• Remove the voltage from the power supply by opening the protective switches.
• Disconnect the measuring test equipment; restore the normal power supply connections.
• Apply voltage to the power supply.
• Close the protective switches for the voltage transformers.
• Verify that the voltage phase rotation at the device terminals is correct.
• Open the protective switches for the voltage transformers and the power supply.
• Check the trip and close circuits to the power system circuit breakers.
• Verify that the control wiring to and from other devices is correct.
• Check the signaling connections.
• Switch the mcb back on.
326
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
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