Siemens SIPROTEC 7SD610 Manual page 314

Mounting and Commissioning
3.3 Commissioning
Figure 3-26
• The power measurement provides an initial indication as to whether the measured values of one end have
the correct polarity.
– If the direction of the reactive power is correct but the sign of the active power is incorrect, cyclic phase
swapping of the currents (right) or of the voltages (left) might be the cause;
– If the direction of the active power is correct but the reactive power has an incorrect sign, cyclic phase
swapping of the currents (left) or of the voltages (right) might be the cause;
– if the signs of both active and reactive power are incorrect, the polarity in address 201 CT Starpoint
has to be checked and corrected.
The phase angles between currents and voltages must also be conclusive. All three phase angles ϕ (U
I ) must be approximately the same and represent the operating status. In the event of power in the direc-
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tion of the protected object, they correspond to the current phase displacement (cos ϕ positive); in the event
of power in the direction of the busbar they are higher by 180° (cos ϕ negative). However, charging currents
might have to be considered (see above).
• The measurements may have to be repeated after correcting the connections.
• The above described tests of the measured quantities also have to be performed at the other end of the
tested current path. The current and voltage values as well as the phase angles of the other end can also
be read out locally as percentage values. Please observe that currents flowing through the object (without
charging currents) ideally have opposite signs at both ends, i.e. they are turned by 180°. In the „WEB-Mon-
itor", the local and remote measured values can be shown graphically. An example is shown in Figure 3-25.
• The protected object is now switched off, i.e. the circuit breakers are opened.
Polarity check for the current measuring input I
If the standard connection of the device is used whereby current input I
of current transformers (refer also to the connection circuit diagram in the Appendix A.3), then the correct po-
larity of the earth current path in general automatically results.
If, however, the current I
is necessary.
The test is done with a disconnected trip circuit and primary load current. It must be noted that during all sim-
ulations not exactly corresponding with cases that may occur in practice, the non-symmetry of measured values
may cause the measured value monitoring to pick up. This must therefore be ignored during such tests.
314
Apparent load power
4
is derived from a separate summation CT, an additional direction check for this current
4
is connected in the starpoint of the set
4
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
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