The IDAX is an insulation diagnostic analyser based on DFR (Dielectric Frequency Response), also known as FDS (Frequency Domain Spectroscopy). DFR technology is an established test procedure in laboratories that, in an innovative effort by Megger, has been adapted for field use in the IDAX range of instruments.

DFR is the measurement of capacitance and losses (tan delta or power factor) over multiple frequencies. The measured DFR curve is dependent on insulation geometry, moisture, oil conductivity, and temperature. By advanced curve fitting to the reference material model, the IDAX calculates moisture content in solid insulation, the oil’s conductivity at 25 °C reference temperature, and tan delta/power factor at 20 °C reference temperature.

In these calculations, ITC (Individual Temperature Correction), another important Megger innovation, is used to translate test data from the test object temperature to the reference temperatures. The IDAX software incorporates an ITC-corrected frequency sweep designed explicitly to assess instrument transformers and bushings.

Thanks to a novel approach to the combination of time and frequency domain data, the IDAX provides the shortest measurement time in the marketplace for a full DFR measurement from 1 kHz to 10 μHz. Separate reference models are fitted to each data set (time or frequency) prior to transformation and combination, which eliminates the risk of artefacts introduced by approximations or transformation of incomplete data sets.

The IDAX is exceedingly easy to use, with an automated test flow and presentation of results that uses an easy-to-understand ‘traffic light’ system.

The IDAX DFR method is now part of international guides and standards, e.g., Cigre TB 254, Cigre TB 414, Cigre TB 445, Cigre TB 775, IEEE C57.152-2013, IEEE C57.161-2018.

The IDAX is available in multiple versions:

• IDAX300 – A compact and light three-channel input (red, blue, and ground), three-terminal (generator, measure, and guard), and one ammeter instrument for use with an external computer that runs the IDAX diagnostic software.
• IDAX300/S – As IDAX 300 but with two ammeters for two simultaneous measurements.
• IDAX350 – As IDAX 300/S but housed in a rugged and waterproof case with an on-board computer that can also be used to control other Megger instruments.
• IDAX322  - AS IDAX 300/S but with built-in 2 kV amplifier for higher signal-to-noise ratio in low capacitive test objects. Ideal for field testing bushings.

For extended applications, the IDAX interfaces seamlessly with VAX high voltage amplifiers; VAX020 for 2 kV and VAX220/230 for 20/30 kV (on request).