Siemens 7SC80 Manual page 476

Mounting and Commissioning
3.2 Checking Connections
•
If the voltage measurement is carried out via feedthrough capacitances, the feedthrough capacitance for
the 7SC80 must be available exclusively.. Parallel connections such as, for example, CAPDIS are not
permissible.
In the case of a voltage measurement via bushing capacitances, the value of the individual capacitances
C1 and C2 for the three phases must be known approximately (also see Section
"Capacitive Voltage Measurement"). These capacitance values are configured via the parameter addresses
241 Volt.trans.A:C1 to 248 Volt.tran.Vx:C2 in the Power System Data 1. The value for the
bushing capacitances (C1) is usually in the range from 5 pF to 10 pF. The values for the line capacitances
(C2) - also including the stray capacitances - basically depend on the cable type used and the cable length
for the measuring voltage connection. Inexactly configured capacitance values will result in deviations
during the measurement of the voltage amplitude and the voltage phase angles.
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
•
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-
circuited.
•
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
polarity 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
charging 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.
476
2.1.3.2 Setting Notes, "Capacitive Voltage Measurement".
2.1.3.2 Setting
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
Notes,