Mounting and Commissioning
3.2 Checking Connections
SIPROTEC, 7SC805, Manual
C53000-G1140-C380-1, Release date 05.2014
92
Caution!
Take care when operating the device without a battery on a battery charger.
Non-observance of the following measures can lead to unusually high voltages and consequently, the destruc-
tion of the device.
Do not operate the device on a battery charger without a connected battery. (For limit values see also Technical
Data, Section 4.1).
Before the device is energized for the first time, it should be in the final operating environment for at least 2
hours to equalize the temperature, to minimize humidity and to avoid condensation. Connections are checked
with the device at its final location. The plant must first be switched off and grounded.
Proceed as follows for checking the system connections:
• Circuit breakers for the auxiliary power supply and the measuring voltage must be opened.
• Check the continuity of all current and voltage transformer connections against the system and connection
diagrams:
- Are the current transformers grounded properly?
- Are the polarities of the current transformer connections the same?
- Is the phase assignment of the current transformers correct?
- Are the voltage transformers grounded properly?
- Are the polarities of the voltage transformer connections the same and correct?
- Is the phase assignment of the voltage transformers correct?
- Is the polarity for current input
I
N
correct (if used)?
- Is the polarity for the voltage input V
3
correct (if used e.g. for broken delta winding or busbar voltage)?
- If the voltage measurement is carried out via feedthrough capacitances, the feedthrough capacitance for
the 7SC805 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 3 phases must be known approximately (also see Section 2.1.2.2, „Capacitive Voltage Mea-
surement“). 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 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 capacitance
- basically depend on the cable type used and the cable length for the measuring voltage connection. Inex-
actly configured capacitance values will result in deviations during the measurement of the voltage ampli-
tude 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
2.1.2.2,”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 MU), check the voltage level and, if applicable, the polarity of
the voltage at the device terminals or at the connection modules.
