Siemens siprotec 7SD5 User Manual page 498

3 Mounting and Commissioning
• The power measurement provides an initial indication as to whether the measured
• The measurements may have to be repeated after correction the connections.
• The above described tests of the measured values also have to be performed at the
• The protected object is now switched off, i.e. the circuit breakers are opened.
Polarity Check for Depending on the application of the voltage measuring input U
the Voltage Input be necessary. If no measuring voltage is connected to this input, this section is irrele-
U vant.
4
If the input U
Data 1 address 210 U4 transformer = Ux transformer), no polarity check is
necessary because the polarity is irrelevant here. The voltage magnitude was
checked before.
If the input U
(P.System Data 1 address 210 U4 transformer = Udelta transf.), the po-
larity together with the current measurement is checked (see below).
If the input U
(P.System Data 1 address 210 U4 transformer = Usync transf.), the po-
larity must be checked as follows using the synchronism check function.
Only for Synchro- The device must be equipped with the synchronism and voltage check function which
must be configured under address 135 Enabled (see section 2.1.1.3).
nism Check
The voltage Ubus connected to the busbar must be specified correctly under address
212 Usync connect. (see Section 2.1.2.1).
If there is no transformer between the two measuring points, address 214 ϕ Usync-
Uline must be set to 0° (see Section 2.1.2.1).
If the measurement is made across a transformer, this angle setting must correspond
to the phase rotation through which the vector group of the transformer as seen from
498
values of one end have the correct polarity.
– If the reactive power is correct but the active power has the wrong sign, cyclic
phase swapping of the currents (right) or of the voltages (left) might be the cause.
– If the active power direction is correct but the reactive power has the wrong sign,
cyclic phase swapping of the currents (left) or of the voltages (right) might be the
cause.
– If both the real power as well as the reactive power have the wrong sign, the po-
larity in address 201 CT Starpoint must be checked and rectified.
The phase angles between currents and voltages must also be conclusive. Each
one of the three phase angles ϕ (U
represent the operating status. In the event of power in the direction of the protected
object, they represent 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 taken into consideration (see above).
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.
Note that currents flowing through the object (without charging currents) ideally
have opposite signs at both ends, i.e. turned by 180°. In the „WEB-Monitor" the local
and remote measured values can be shown graphically. One example is illustrated
in Figure 3-27.
is used for measuring a voltage for overvoltage protection (P.System
4
is used for the measurement of the displacement voltage U
4
is used for measuring a busbar voltage for synchronism check
4
–I ) must be approximately the same and must
Lx Lx
, a polarity check may
4
en
7SD5 Manual
C53000-G1176-C169-1