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FRAX User's Manual
© 2011 Megger Sweden AB
5.4
Appendix D: Sweep Name Settings
There are two predefined sweep plans for each language, one IEEE based on the DRAFT D9 of
the IEEE PC57.149 and one IEC based on CIGRE Brochure 342, 2008 and a draft of IEC 60076-18.
All predefined sweep plans can be modified to suit your use. To do so use the buttons "Add"
and "Delete". The names can be changed by selecting a "Sweep group" or "Sweep name" and
enter a new name. Select a "Sweep group" and select which Sweeps that should be included
by setting the cross in front of the sweep name(s) and then hit "OK".
The files containing the sweep plans are located in the MeasData directory, e.g. for Windows
XP at
C:\Documents and Settings\User1\Application Data\FRAX\MeasData
. The modified
sweep groups can be found in
X_Edit_DefaultTemplates.xml
in respective folder for selected
language. If you make new sweep groups and want to distribute them you can use the file
UserTemplates.xml and rename it to a suitable name. When adding a sweep plan file just put
it in the
MeasData
directory, at e.g. for Windows XP at
C:\Documents and Settings\User1
\Application Data\FRAX\MeasData
and the FRAX software will read from it. Note that the
available sweep plans are displayed in alphabetical order based on the sweep plan file so if
you want to make sure your own sweep groups are displayed first name the file to something
like
1custom.xml
or
!!myfile.xml
.
The basis of FRA analysis is comparison with reference measurements; if reference
measurements are available, it is strongly recommended to repeat those measurements
exactly as the reference measurements were set up.
For all new measurements the current drafts of IEC and IEEE have some differences. Also the
phase labeling is different, note however, you can always change name in the template, e.g.
change 1u, 1v and 1w to e.g. R, S and T.
In the IEEE Draft of PC57.149, it is recommended to follow the basic principle to measure
windings from head-to-tail and consequently the recommended test connections will depend
on winding configuration. The pre-defined templates in FRAX 2.5 covers the most common
types of configurations/vector groups and you may change direction of low voltage and
tertiary winding measurements to comply with the IEEE recommendation. The recommended
measurements are the end-to-end measurements both open and short-circuited and others are
optional. The De-Energized Tap Changer (DETC) should be in position as found and recorded
in Nameplate, Load Tap Changer (LTC) shall be set in Extreme Rise position (also to be noted
in nameplate). See Sample Connections below.
In the DRAFT of IEC 60076-18 it is recommended to measure all windings End-to-End Open,
and the winding with a load tap changer in “Max” i.e. the LTC position that place all LTC
winding in series, and the LTC in a position that does not include the regulating winding,
called OUT-position in template. Note that End-to End Short-circuit is optional. IEC also
recommends to measure in the direction referring to bushing labeling, i.e. no modification is
necessary to measure an YnYn6 compared to an YnYn4, and this is taken care of in the
implementation.
If delta windings can be split into individual phases (six bushings brought out) then the
measurement shall be made with the windings split. For large generator transformers where
it is inconvenient to remove the phase to phase connections in service it is recommended that
the baseline measurement in the factory and during commissioning is performed both with
the delta open and closed.
For delta tertiary or stabilizing windings, the delta shall be closed. For delta tertiary or
