Megger DELTA4000, Instruction Manual, Page: 62 / 74

M
AVTMDELTA4000-EN Rev 6 April 2018
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Standard Temperature Correction Tables
This is the standard correction method based on tables for various components.
For power transformers the table selection is based on manufacturing year,
transformer type (sealed, free breathing etc), voltage and power rating. For
bushings the table is selected by manufacturer and type.
Individual Temperature Correction, ITC
As a unique feature DELTA4000 also offers ITC, Individual Temperature
Correction. With ITC the actual temperature correction for a certain
measurement object is estimated by measuring an additional frequency sweep
after performing the standard single frequency measurement. The information
from the sweep test is then used to estimate the correct temperature correction
from measurement temperature to 20°C reference (patent pending).
Test # Column Blue coloured numbers care depressed to begin a test. If
Multiple Test is enabled, all tests for a specific group are sequentially completed.
DFR if these boxes are checked, a frequency sweep test is conducted and
displayed in the DFR Graph below the Overall Tests.
Individual frequencies are defined in a list in PDB settings. The maximum
frequency range is pending the test voltage as described in the following table.
Test Voltage Maximum frequency
range
12 kV 45-70 Hz
4 kV 15-405 Hz
2 kV 8-505 Hz
1 kV 4-505 Hz
500 V 2-505 Hz
250 V 1-505 Hz
Note: Do not select the power frequency or any multiple of power frequency in a
frequency sweep, e.g. in 50 Hz networks avoid, 50, 100, 150… and in
60 Hz networks avoid 60, 120, 180…
Voltage Dependence Detection
Another unique feature in DELTA 4000 is automatic Voltage Dependence
Detection (patent pending). In every test, DELTA4000 measures the harmonic
content of the signal and based on this information it calculates a Voltage
Dependence Factor, VDF. If this value is too high (default > 0.5) the number
turns red, indicating a voltage dependence of the test object i.e. the dissipation