1. IDAX 300 Insulation Diagnostic Analyzer Dielectric Frequency Response Also known as: Frequency Domain Spectroscopy

2. Typical power factor values @ 20° C
Typical power factor values for oil insulated transformers and bushings
Typical power factor 20° C
"New"
"Old"
Warning/alert limit
Power transformers, oil insulated %
< 0.5%
> 0.5%
Bushings (OIP) %
< 1%
> 1%
IEEE states; “The power factors recorded for routine overall tests on older apparatus provide information regarding the general condition of the ground and inter-winding insulation of transformers and reactors. While the power factors for most older transformers will also be <0.5% (20C), power factors between 0.5% and 1.0% (20C) may be acceptable; however, power factors >1.0% (20C) should be investigated.”

3. Megger test sets for capacitance/tan delta testing
Application/Measurement
CB100
IDAX300
DELTA4000
Power frequency tan delta/power factor
Yes
Capacitance measurements
High voltage tan delta/power factor No
Yes (VAX)
High power tan delta/power factor
Frequency range
0.1 mHz-10 kHz
1-500 Hz
Moisture assessment
Individual temperature correction
Temperature dependence analysis
Tip-up testing

4. DFR/FDS measurement setup
Measure at several frequencies
Use Ohms law:

5. Dielectric Frequency Response / Frequency Domain Spectroscopy
Changes in insulating materials (ageing) affect the capacitance and loss factor (PF, tan)
Measuring a frequency response, compared to traditional power frequency dissipation factor and capacitance measurements, provides a lot more information on:
Insulation characteristics
Moisture/Ageing effects
Influence of temperature
Etc…
DFR is the tool for investigation!

6. DFR/FDS - 100 years of history
1870’s; First systematic investigations of dielectric properties (Clausius and Mosotti)
1885; The transformer is invented by Ottó Bláthy
1927; First Megger for DC insulation testing is patented and released
1990; ABB presents first results on dielectric response measurements on insulating materials combined with model-based signal analysis of cellulose insulation (NORD-IS 1990)
1993; Development of the first field instrument for Dielectric Frequency Response measurements is started by Dr. Peter Werelius
1995; First IDA (Insulation Diagnostic Analyzer) instrument delivered
; The interest in using DFR/FDS for investigating insulation properties is rapidly growing and numerous papers on the method and technology are presented at international conferences
2004; CIGRE report 254, ”Dielectric Response Methods for Diagnostics of Power Transformers” is published
2006; Project REDIATOOL reported at CIGRE, recommending DFR as a preferred method for moisture assessment of power transformers
2009; CIGRE report 414 “Dielectric response diagnoses for transformer windings” finalized and published

7. Methods for DFR measurements
DC (Polarization-Depolarization Current measurements)
Strenght
Shorter measurement time at very low frequencies
Weaknesses
More sensitive to AC interference (microamps...)
More sensitive to DC interference (nanoamps...)
Limited frequency range (PDC only)
Data conversion necessary (combined PDC/DFR only)
Discharge before measurement may be needed
AC (Dielectric Frequency Response measurements)
Strenghts
Less sensitive to AC interference (milliamps...)
Less sensitive to DC interference (microamps...)
Wide frequency range
No data conversion
No discharge necessarry
Weakness
Longer measurement time for very low frequencies 7

8. Noise in substations Induced AC (50/60Hz)
Induced DC (Corona discharge)
Induced DC (HVDC stations)
DC offset from (varying) ground potential (mainly in HVDC substations)
Other disturbancies (RF, power transients etc)

9. Max noise interference for different measurement technologies
Noise susceptibility
Noise source
Max noise interference for different measurement technologies
LV DC/PDC (Omicron)
LV AC (IDAX )
HV AC (IDAX300+VAX020, Delta4000)
Amplitude
SNR
AC (50/60Hz)
~ 10 µA (?)
not stated
~ 1 mA
1:2
~ 15 mA
~ 1:20 DC
”very sensitive”
”not sensitive”

10. Dielectric Frequency Response - Dissipation Factor Changes with Frequency
Tan delta
/power factor
0.32 at 0.02 Hz
at 60 Hz
Frequency

11. What affects the response?
- Oil Conductivity +
- Moisture +
- Temperature +

12. Dielectric Frequency Response - Single value @ 0
Dielectric Frequency Response - Single 0.7% is not sufficient to make the right decision - Dielectric Frequency Response tells the story!
Wet transformer with good oil (low conductivity)
Dry transformer with bad oil (high conductivity)
Same PF value at 60Hz

13. DFR Application Areas Power transformers Bushings
Instrument transformers
Motors and generators
Insulating oil
Cables
Generic testing of any insulation system

14. IDAX 300 – Insulation Diagnostic Analyzer

15. VAX020/214/230 – High Voltage Amplifiers

16. IDAX Test System HW SW Test signal: 0 – 200 V, 50 mA (IDAX300)
0 – 2kV, 50 mA (with VAX020)
0 – 10 kV, 40 mA (with VAX214)
0 – 30 kV, 40 mA (with VAX230)
Frequency: Hz – Hz
Capacitance range: 10 pF – 100 µF
Max interference: 1 mA or 1:2 50/60 Hz (IDAX300)
15 mA or 1:20 SNR (IDAX+VAX)
2-ch measurement: Multiplexing (IDAX300)
Simultaneous (IDAX300S) SW
IDAX SW for measurement control and analysis
MODS SW for:
Automatic moisture assessment of oil impregnated cellulose
Temperature dependence analysis by conversion of frequency data to temperature data
Individual temperature correction from measurement temperature to 20° reference

17. IDAX300 with VAX020

18. VAX020 – What? High voltage amplifier for IDAX300/350
Increases IDAX 300/350 output voltage from 200 V to 2 kV
Technical specification
2 kV output (peak)
DC – 1 50 mA max current
Capacitance range
4 1 Hz
80 50 Hz (67 60 Hz)
4 1 kHz

19. VAX020 – Why?
Key benefits;
DFR in substations with high DC or extreme low frequency AC interference, e.g. HVDC substations
2 kV DFR up to 1 kHz especially for low capacitance objects, e.g. insulating oil, CTs and not mounted bushings
2 kV capacitance and tan delta testing at power frequency
Tip-up testing

20. DFR summary and conclusions
Dielectric response measurement is an excellent tool for insulation diagnostics on power transformers, bushings, CT/VTs, generators, motors etc
Moisture assessment using DFR and transformer insulation modeling is a generally accepted standard measurement method
DFR together with insulation modelling can perform individual temperature correction and temperature dependence analysis
AC and DC interference is common in substation environment – Choose a DR method with low noise susceptibility – An IDAX/VAX system!

21. The doctor is in...