18
Field Testing and Commissioning
7UT51 v3
202 PRIM-2330C
If the phase angles are correct, the differential and
stabilizing currents can be checked in Address 4161. If
considerable differential currents occur, recheck the
concerned parameters as is Sections 18.3.1. If these
parameters are changed now, the complete tests with
Side 1 against Side 2 would need to be repeated.
The symmetrical current tests are now complete.
Disconnect the protected object and ground,
disconnect the test arrangement.
18.4 Preparation for Zero
Sequence Current Tests
The zero sequence tests are necessary with
7UT513, if:
• zero sequence current correction by means of one
of the additional measured current inputs IA or IB
is carried out with transformer differential
protection, i.e. addresses 7806 and/or 7807 are
assigned to a transformer winding, which is
parameterized to Io-Correction (addresses 1106
or 1126 or 1146),
or
• the restricted earth fault protection is used, i.e.
addresses 7806 and/or 7807 are assigned to a
side of the protected object or virtual object, which
is also assigned to the restricted earth fault
protection.
Besides this, the neutral of the respective winding
must be grounded and a current transformer must be
installed in the ground lead of that winding.
Zero sequence current measurement is always
performed from the side of the protected object where
the transformer is grounded. The transformer must
have a delta winding. The sides not included in the
test can remain open as the delta winding ensures that
the zero sequence current path is low impedance
circuited. See Figure 18.2 for example test
arrangements.
18.4.1 Zero Sequence Tests –
Address Block 4100
Inititation of test is again made via the relay front panel
or PC. If the test arrangement is changed, a new
measurement is necessary.
As soon as the first measured value appears in the
display the test current can be switched off.
Since the results of the symmetrical current tests have
already been checked, only the results of the zero
sequence current tests are relevant now. The
remaining results can be bypassed by pressing the
No
key. The displayed currents are referred to the rated
current of the relay.
Go to Address 4101 to initiate the differential test.
After confirmation is carried out. The relay measures
all currents and phase angles of this test address. If
wrong values occur for the additional currents IA and/
or IB, the test arrangement must be rechecked.
Additionally, recheck and correct the relevant
configuration parameters in Address 7806 for
measured current IA, and Address 7807 for measured
current IB.
The test differential current value of IA and/or IB
should be approximately three times the line currents.
If not connected “****” will be displayed.
Continue on to the angle measurement test in
Address 4141. The phase angle relation of the phase
current need not be checked. The phase angles of all
phase currents of the winding under test against each
other are zero, those against different windings are not
defined because of missing current. Therefore, page
on to Address 4141. The phase angles, between the
star-point current connected to input IA or IB against
the phase current, are displayed. Numerical values
are to be expected only for those current inputs which
are included in the test current path, for the remaining
currents, “
****
” is displayed.
If an additional current input is not assigned to any
side of the protected object (addresses 7806 and/or
7807), the associated measured values do not appear
at all.
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