IDAX series of insulation diagnostic analysers
Measure moisture content, tan delta/power factor and oil conductivity using DFR in the field - IDAX300/300S, IDAX322, IDAX350
Measure moisture content, tan delta/power factor and oil conductivity using DFR in the field - IDAX300/300S, IDAX322, IDAX350
Key Benefits
- Fastest system in marketplace
- Reliable measurements in high interference environments
- Automated individual temperature correction (ITC)
- Dedicated test procedures
Description
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).
Specifications
Frequently Asked Questions
How can moisture affect bushings and current transformers?
Moisture ingress is a relatively common problem with bushings and current transformers that can have catastrophic consequences; bushing malfunction is the cause of 17 % of all transformer failures and up to 70 to 80 % of all transformer fires. A failing bushing is also likely to explode, potentially damaging the entire substation.Performing traditional tan delta or power factor tests at line frequency is not enough, as such testing can give false positive results; only through DFR can you access the true status of a bushing or instrument transformer. In addition to catching high moisture levels, DFR has successfully detected traces of partial discharges in HV and EHV bushings.
What makes the IDAX so fast?
Any time that you can perform an entire measurement in only FDS (frequency domain spectroscopy) mode, you have a better, more reliable measurement. A true frequency domain method that speeds up measurement time is accomplished by applying several frequencies simultaneously, and extracting measurement data from the applied frequencies simultaneously. Because the voltage level of each frequency needs to be reduced, the measurements are a bit more sensitive to AC interference, but DC current interference will not affect the measurements. This multi-frequency approach is an advance over the older approach of combining FDS with PDC, which is more sensitive to AC interference and also quite sensitive to DC interference.The time savings of the multi-frequency method are significant. For example, using three frequencies simultaneously reduces measurement time by about 40 %.
What is the IDAX used for?
One of the most critical applications for the IDAX is determining the moisture content in transformer insulation. Moisture in the insulation significantly accelerates the ageing process. Moisture can cause bubbles between windings, resulting in catastrophic failures. The IDAX provides reliable moisture assessments in one test. You can perform the test at many temperatures; it can take upwards of 20 minutes or more, depending on the condition and temperature of the test object.
When would a VAX also be required?
When testing low capacitance objects like bushings and current transformers, the IDAX paired with the VAX020 provides a test voltage of up to 2 kV, giving an excellent signal-to-noise ratio and measurement up to 1 kHz. A unique single-material version of ITC brings test results to a reference temperature regardless of the test object temperature. IDAX supports OIP, RIP, RBP, OIP CT, and user-defined materials.With the 20/30 kV amplifiers (VAX220), the IDAX can be used to assess the status of XLPE cables. Frequency sweeps are done at 25 %, 50 %, 75 %, and 100 % of service phase-to-ground voltage, and by comparing DFR curves, water treeing can be detected. DFR makes it possible to separate the characteristic response of water trees from the influence of accessories and creep currents.
How can testing preserve the life of transformers?
Maintenance (or replacement) decisions about a transformer should be informed by the unit's insulation condition and expected loading. Adding just a few operational years to the predicted end-of-life for a transformer (or generator, or cable) by optimising its working condition based on reliable diagnostic data means substantial cost savings for the equipment owner.A transformer owner can also use FDS technology to assess the condition and ageing of the insulation in bushings, CTs, VTs, and other components. Numerous ongoing research projects at institutes and universities worldwide are adding experience and value to users of the IDAX.
How can moisture affect power transformers?
Moisture that accumulates in the insulating system of a power transformer affects several properties: Limits the loading capability as higher moisture levels decrease the bubble inception temperature Lowers the dielectric strength of the oil, which has a direct effect on the insulation properties Ages the cellulose insulation, lessening its mechanical strength as a consequence DFR by IDAX is the only reliable method to determine the humidity in power transformers without decommissioning or disassembly. Typically, single-frequency tan delta/power factor tests can give incorrect results due to temperature effects, and oil analysis is unreliable as moisture mainly resides in the solid insulation. In a power transformer application, the IDAX uses a unique two-material model and ITC to accurately calculate humidity, oil conductivity, and tan delta/power factor.
For which applications do I need a high voltage (HV) DFR instrument like the IDAX322?
The most commonly used voltage level is 140 V RMS, which is enough to measure a transformer’s CHL insulation in most conditions. However, in situations where there is a high level of interference or when measuring CH or CL (of a transformer), reactors, bushings, and current transformers (CTs), a 140 V RMS signal does not provide a high enough measurement signal-to-noise ratio to get meaningful results. A higher test voltage, like the IDAX 322’s 1400 V RMS/2000 V peak, will improve the measurement accuracy and is recommended in these instances.
Why is having two ammeters in a DFR test set (a feature unique to the Megger IDAX range of instruments) important?
The benefit of having two available metering systems in one instrument is the unique advantage of testing two capacitances simultaneously. For example, the IDAX can test two HV bushings at the same time. It can also simultaneously measure both of a three-winding transformer’s interwinding insulation systems, e.g., CLH and CLT.No other instrument is capable of simultaneous measurement in the frequency domain. In some dual-channel instruments, both channels share a single ammeter. With these instruments, either half as many measurements are made (i.e., less accuracy), or no timesaving is realised compared to performing two separate tests.
Documents
- IDAX300-350_DS_en.pdfpdf 738.29 KB
- IDAX322_DS_en.pdfpdf 674.77 KB
- IDAX300-350-AN_EN_Novel-Approach-DFR-Speed.pdfpdf 406.16 KB
- Misleading_LFPF_CaseStudy5_EN_V01.pdfpdf 11.93 MB
- Dielectric-commissioning-CaseStudy4-EN-V04.pdfpdf 2.57 MB
- Transformer Magazine - Individual temperature compensation 42-47.pdfpdf 382.75 KB
- 1-500Hz_AnalysisBushings_CaseStudy_V01.pdfpdf 7.61 MB
- 200401 Case Study on Idax+Vax020 (002).pdfpdf 1.58 MB
- DFR_WP_EN_V01.pdfpdf 1.2 MB
