Megger DELTA4000, Instruction Manual, Page: 61 / 74

Performing Tests within Forms
AVTMDELTA4000-EN Rev 6 April 2018
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NOTE: Once Tests 5, 6 and 7 are completed, Line 8 will populate with values
calculated by subtracting Test 6 from Test 5. This is applicable for
values of capacitance, current and watts. Line 8 is a calculated
comparison to the direct measurements of Test 7. Values on these two
lines should be essentially the same. If they are not, re-check all
connections and verify the proper operation of the test set. If Test 7 and
Line 8 vary by more than 2%, the Insulation Rating (IR) will
automatically populate with B (Bad).
Lines 9 and 10 will automatically populate with calculated values once Tests 1-7
and all bushing tests are completed. Line 9 is a corrected value for the insulation
of the high voltage winding to the transformer tank minus the measured losses
of the high side bushings. Line 10 is a corrected value for the insulation of the
low voltage winding to the transformer tank minus the measured losses of the
low side bushings.
Oil Tests
The 93500 test form includes two tests for capturing the results of a power
factor test on the insulating oil. This is generally done on a sample of oil drawn
from the main tank of the transformer under test and a sample of oil drawn from
the OLTC. The test requires an oil test cell designed for field use. The test cell
should be a three-terminal cell where connections for high voltage, measurement
lead, and ground can be safely made.
As with the other insulation tests on this test form, the test sequence is initiated
by left-clicking on the blue highlighted test number at the bottom of the Overall
Tests table. The test mode used is UST-R.
Overall Test Options
Multiple Test enables/disables the ability to perform groups of tests associated
with common test connections. This saves time, as all tests are conducted
sequentially until complete. With this example, 1/2/3 are tested together and
5/6/7 are tested together.
Hook up Diagram enables operator to view the connection diagram for the
specific test to be conducted
Temperature Correction Table/ITC toggles selection for correction to 20C as
seen below. Correction tables are based on “year, KVA & voltage” from
Nameplate Input.
Change Temperature Correction Table/Set ITC allows operator to change
the correction table used (if Temperature Corr Table selected) or allows the
operator to perform an ITC test where the specific transformer’s
Individual
Temperature Correction is determined and applied to results.