Omicron Lab CT Analyzer, User Manual

Page: 110 / 254

CT Analyzer User Manual
108
6.6 Excitation Card
The Excitation card is only available if it is enabled in the Select Cards page
(Default Test Card Selection or Select Cards soft key in the CT-Object card).
The excitation test is used to trace the excitation curve of the current transformer
and to determine many CT-specific parameters (see test results below). The test
is done completely automatically up to a current of 15A
peak
.
CTs with closed cores can be tested up to a knee point voltage of 30kV. For CTs
with gapped cores the maximum test voltage and current are limited depending
on the maximum output power of the device. Typical maximum current and
voltage values for a TPZ core are 9A
rms
at 1200V
rms
.
The settings for the excitation test are specified in the CT-Object card. For a
better understanding of the test results, the most important settings from the
CT-Object card are shown in the upper part of the Excitation card.
The test results displayed in the lower part of the Excitation card depend on the
standard selected in the CT-Object card. Using the soft keys, the user can
choose between different sets of results. If the Results with Nom. Burden soft
key is pressed, the page shows the results related to the nominal burden ("VA"
parameter in
CT-Object card). If the Results with Op. Burden soft key is
pressed, the page shows the results related to the operating burden ("Burden"
parameter in
CT-Object card).
Pressing the Excit. Graph soft key opens a page with the excitation graph (see
page 114).
Pressing the AL Error Graph soft key opens a page with a graph showing the
maximum possible primary current (K * I
pn
) that can flow over a specific burden
without exceeding the accuracy limit (5% or 10%).
Figure 6-12 Excitation card with values related to nominal burden
If the CT Analyzer displays an overload in the Excitation card, either the desired
knee point could not be reached or not all necessary measurement points could
be taken (e.g. in the knee point area, not enough points for a proper calculation
of the knee point could be measured).