MEGGER

Transformer Insulation Testing

The primary test methods used to assess the condition of the active insulation components in transformers and bushings, on site, include:

1) power factor/tan δ,
2) variable frequency power factor/tan δ (1 - 500 Hz)
3) dielectric frequency response (DFR) [a dielectric response method], and
4) moisture in oil measurements (for transformers).

A traditional power factor/tan δ test provides some useful information for the assessment of insulation but the analysis may be elusive so relying exclusively on this method reduces the success of the test program, in part, to luck.

For a far more effective and reliable test program, variable frequency power factor/ tan δ measurements and dielectric frequency response (DFR) tests should be incorporated as well.

Variable frequency power factor/tan δ testing complements the power factor/ tan δ measurement by enabling the determination of the insulation system’s unique, or individual, temperature correction (ITC) factor and generally serves as a better screening diagnostic. Megger’s DELTA4000 automatically produces the ITC for each transformer and provides confidence that the power factor/ tan δ result is accurately corrected to a 20°C equivalent value. The easy-to-use software interface, PowerDB, minimizes time required to learn how to use the DELTA4000 and perform these tests correctly.

Meanwhile, dielectric frequency response (DFR) testing delivers a very reliable and accurate moisture assessment of the insulation and the conductivity of the oil. A thorough review of DFR elucidates why this is a better tool for moisture assessment than traditional moisture in oil measurement, which deduces the moisture content in cellulose from the measured moisture in oil. Megger’s IDAX is a best-in-class dielectric response analyzer and the only instrument that can perform true FDS measurements (which is the preferred DFR method due to its robustness against noise) all the way down to 0.1 mHz in record time. A noteworthy accessory for the IDAX is the VAX, an amplifier that boosts the output signal of the IDAX to 2 kV, which may be important for low capacitive specimens, particularly CTs, to obtain meaningful moisture measurements.New Paragraph

CDAX 605
HIGH-PRECISION C AND DF MEASUREMENT INSTRUMENT

  • High accuracy and wide measurement range
  • Automatic measurement process
  • Measures capacitive, resistive or inductive test objects
  • High accuracy ratio measurements
  • Works with any standard capacitor or resistor value without any recalculations
  • All standard UST and GST configurations
CDAX 605 is a capacitance and dissipation factor test set to be used with an external power source/generator. It is a precision instrument using a combination of bridge and direct (vector) measurements and is capable of measuring capacitive, resistive and inductive loads.

CDAX 605 is designed for laboratory, production line or field testing of electrical equipment insulation and insulating materials as well as e.g. calibration of CCVTs and other ratio devices. A test set with unique high accuracy for the most demanding applications.

DELTA4000 Series
12 KV INSULATION DIAGNOSTIC SYSTEM

  • Power factor test set
  • Automatic and manual operation
  • Accurate and repeatable measurement results with high noise suppression
  • Lightweight, rugged two-piece design
  • New built-in intelligent temperature correction (patent pending)
  • New automatic voltage dependence detection (patent pending)
DELTA4000 series is a fully automatic 12 kV insulation power factor / dissipation factor (tan delta) test set designed for condition assessment of electrical insulation in high voltage apparatus such as transformers, bushings, circuit breakers, cables, lightning arresters, and rotating machinery.

Two configurations make up the series:

DELTA4110 with external computer (not included) consists of the DELTA4100 control unit and DELTA4010 high-voltage unit
DELTA4310A touch display interface comes with onboard computer, PowerDB software and printer and allows connection to and control of MWA300, TTR300/310E, MTO300, MLR10 and some Megger insulation resistance instruments. 

FRAX99, FRAX101 and FRAX150
SWEEP FREQUENCY RESPONSE ANALYSERS

  • Highest dynamic range and accuracy in the industry
  • Smallest and most rugged FRA instrument in the industry
  • Fulfills all international standards for SFRA measurements
  • Advanced analysis and decision support built into the software
  • Imports data from other FRA test sets
The FRAX series of sweep frequency response analyzers (SFRA) detects potential mechanical and electrical problems that other methods are unable to detect. Major utilities and service companies have used the FRA method for more than a decade. The measurement is easy to perform and will capture a unique fingerprint of the transformer. The measurement is compared to a reference fingerprint and gives a direct answer if the mechanical parts of the transformer are unchanged or not. Deviations indicate geometrical and/or electrical changes within the transformer.

IDAX300 and IDAX350
INSULATION DIAGNOSTIC ANALYSER

State-of-the-art measurement of moisture content, tanδ and oil conductivity using DFR (Dielectric Frequency Response)
Easy-to-use: Software with automated measurement flow and analysis of test results
“Traffic light” interpretation of test results
Dedicated test procedures for power transformers, bushings and current transformers
Automated individual temperature correction (ITC) for accurate comparison with reference data/tests
Reliable measurements even in high-interference environments
Interfaces to high voltage amplifiers
Versions with or without on-board computer
IDAX is an insulation diagnostic instrument 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.
 
In short, DFR is the measurement of capacitance and losses (dissipation factor (tanδ) or power factor) over multiple frequencies. The measured DFR curve is dependent on insulation geometry, moisture, oil conductivity and temperature and through advanced fitting to a reference material model moisture content, predominantly in solid insulation, oil conductivity at 25°C reference temperature and tanδ at 20°C reference temperature can be calculated. In the calculations ITC (Individual Temperature Correction), another important Megger innovation is used to translate test data from the test object temperature to the reference temperatures. It the latest release, the IDAX SW incorporates a new ITC corrected frequency sweep specifically designed for assessment of instrument transformers and bushings. IDAX is exceedingly easy to use with an automated test flow and presentation of results in an easy to understand “traffic light” manner.
 
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
 
IDAX is available in multiple versions:
IDAX 300 – A compact and light 3-channel input (red, blue and ground), 3 terminal (generator, measure and guard) and one ammeter instrument for use with an external computer that runs the IDAX diagnostic software.
IDAX 300/S – As IDAX 300 but with two ammeters for two simultaneous measurements.
IDAX 350 – As IDAX 300/S but housed in a rugged and waterproof case together with an onboard computer that can also be used to control other Megger instruments.
 
For extended applications IDAX interfaces seamlessly with VAX high voltage amplifiers; VAX020 for 2 kV and VAX220/230 for 20/30 kV (on request).

VAX020
2 KV HIGH VOLTAGE AMPLIFIER FOR IDAX300

  • Separate high voltage amplifier enables capacitance and dissipation factor measurements at 2 kV test voltage
  • True and proven DFR/FDS technology for highest performance
  • Large frequency range, DC to 1 kHz
  • Compact design, weight < 5 kg
VAX020 expands the IDAX300 test voltage range from 200 V to 2 kV. This improves the capability to perform accurate measurements in extreme high interference environments e.g. HVDC substations.
Besides 50/60 Hz capacitance and dissipation factor (power factor) measurements, the application gives valuable information about the general condition of any high voltage insulation by measuring its dielectric response. The technique is also capable of assessing the moisture content in oil/paper insulation systems.
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