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

Typical power factor values @ 20° C Typical power factor values for oil insulated transformers and bushings   Typical power factor values @ 20° C "New" "Old" Warning/alert limit Power transformers, oil insulated 0.2-0.4% < 0.5% > 0.5% Bushings (OIP) 0.2-0.3% < 1% > 1% IEEE 62-1995 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.”

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

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

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!

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 1995-2005; 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

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

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)

Max noise interference for different measurement technologies Noise susceptibility Noise source Max noise interference for different measurement technologies LV DC/PDC (Omicron) LV AC (IDAX300 4.0) 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”

Dielectric Frequency Response - Dissipation Factor Changes with Frequency Tan delta /power factor 0.32 at 0.02 Hz 0.0031 at 60 Hz Frequency

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

Dielectric Frequency Response - Single value @ 0 Dielectric Frequency Response - Single value @ 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

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

IDAX 300 – Insulation Diagnostic Analyzer

VAX020/214/230 – High Voltage Amplifiers

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: 0.0001 Hz – 10000 Hz Capacitance range: 10 pF – 100 µF Max interference: 1 mA or 1:2 SNR @ 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

IDAX300 with VAX020

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 kHz @ 50 mA max current Capacitance range 4 µF @ 1 Hz 80 nF @ 50 Hz (67 nF @ 60 Hz) 4 nF @ 1 kHz

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

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!

The doctor is in...