1 Hz testing with Megger's insulation diagnostics systems
Power factor/dissipation factor testing at 1 Hz
Power factor/dissipation factor testing at 1 Hz provides confidence in 50/60 Hz insulation condition assessment.
With one instrument and one connection, one test provides immediate, reliable decision making for critical high voltage assets.
Our 1 Hz provides dependable insights into insulation health, supplementing traditional 50/60 Hz tests with enhanced sensitivity.
This means smarter maintenance planning, extended asset life and optimised budget utilization.
1 Hz testing versus 50/60 Hz testing
50 Hz / 60 Hz
- Power factor/dissipation factor values react slowly to changes in solid and liquid insulation
- Effects of moisture in the paper and contamination in the insulating liquid are hidden
- A transformer in service for 50 years may measure nearly the same power factor tan delta values as it did when it was new
1 Hz
- Power factor tan delta values react quickly to changes in solid and liquid insulation
- Effects of moisture in the paper and contamination in the insulating liquid are amplified
- A transformer in service for 50 years will show clear changes at 1 Hz, where 50 Hz or 60 Hz cannot
The products that make it possible
FAQs
In the field, it is common to measure PF/DF at power frequency and obtain results within acceptable limits. However, these measurements can be inconclusive because they may not change until insulation is severely degraded. Compared to power frequency PF/DF, 1 Hz is up to 10 times more sensitive to insulation changes and provides immediate confirmation of insulation degradation or contamination.
Absolutely. Assessment of PF/DF may be incorrect without proper temperature correction. However, temperature correction tables do not apply to 1 Hz measurements. Further, even if temperature correction tables could be used, IEEE C57.12.90 states that no single correction curve will fit all cases. To address this, Megger’s DELTA4000 and TRAX + TDX use measurements of PF/DF from 1 Hz to 505 Hz to provide Individual Temperature Correction (ITC), temperature correction based on the actual condition of the insulation.
No! 1 Hz and ITC tests use the same test connection as 10 kV power frequency tests. The software is preconfigured to execute the tests and display results alongside the power frequency results.
At lower frequencies, the sensitivity of dielectric changes due to moisture or contamination increases. This means that 1 Hz values will be higher and increase sooner than line frequency power values. Therefore, 20 °C corrected 1 Hz and power frequency measurement is an effective tool to identify early and advanced degradation and potential failure the insulation of HV components such as transformers and bushings.
1 Hz PF measurement can be performed with a dedicated DFR instrument (IDAX 300 series), or with the same equipment used for 10 kV power factor/dissipation factor testing (DELTA 4000 or TRAX + TDX).
1 Hz is a proactive way to validate the commonly used power frequency PF/ DF results.
a. Mismatch in the assessment of power frequency vs 1 Hz results properly corrected to 20 °C by ITC algorithm is indicative of progressive degradation of the insulation material.
b. It provides confidence on the dielectric assessment and elevates the safe and reliable operation of HV assets.
c. Asset managers and maintenance specialists rely on trustable test results to assure extended service life of critical components within the electrical network.
