IEC 62478IEC 62478

A Prospective Standard forA Prospective Standard forAcoustic and ElectromagneticAcoustic and Electromagnetic

Partial Discharge MeasurementsPartial Discharge Measurements

Michael MuhrMichael Muhr Univ.-Prof. Dipl.-Ing. Dr.techn. Dr.h.c.Univ.-Prof. Dipl.-Ing. Dr.techn. Dr.h.c.

Institute of High Voltage Engineering and System Management Institute of High Voltage Engineering and System Management University of Technology GrazUniversity of Technology Graz

M. Muhr

IEC 62478

Partial Discharge (PD) MeasurementPartial Discharge (PD) Measurement

Sensitive nondestructive method as important diagnostic tool

for evaluation of the insulation condition

PD-defect

Location and Detection

Electrical Non electrical methods

M. Muhr

IEC 62478

Partial Discharge MeasurementPartial Discharge Measurement

Optical

Mechanical

Chemical

Acoustic

Opto-acoustic

HV

Electrical IEC 60270

HF/VHF/UHF

Optical Effects(Light)

Pressure Wave(Sound)

Discharge EffectsDielectric LossesHigh Frequency

Waves

Chemical Effects

Heat

Macroscopic-Physical

EffectsDetection Methods

M. Muhr

IEC 62478

PD-Detection Methods PD-Detection Methods IEC 60270IEC 60270

• Conventional electrical measurement- Integration at frequency domain

Narrow-bandWide-band

- Integration at time domain

G

ZFilter

HV-Source

Test object

Coupling capacitor

PD-System

HVmeasure

PDPulse

QuadripoleMeasuring impedance

M. Muhr

IEC 62478

PD-Detection MethodsPD-Detection Methods

• Electrical measurements with high frequencies

- HF / VHF method – 3 MHz to 300 MHz

- UHF method – 300 MHz to 3 GHz

• Acoustic measurements – 10 kHz to 300 kHz

• Optical measurements – ultraviolet – visible – infrared range

• Chemical measurements

- Optical- Chemical

Directional microphone

PD

HV Acoustic

M. Muhr

IEC 62478

Fiber-optic cable

Infrared camera

Eye Optical sensor

Coronascope

Light produced during the discharge

Low-light enhancer

Optical detection and localisation

Outside not accessible: - Fibre-optic cable- Collimator- Photodiodes

Outside accessible:- Eye- Low-light amplifier- Coronascope

Optical – PD-MeasurementOptical – PD-Measurement

M. Muhr

IEC 62478

PD – Optical DetectionPD – Optical Detection

Measuring circuit after IEC 60270 and optical measuring system

Optical fibre with lens

Optical fibreLens

Peak

Medium oil

Observation area

Fluorescent optical fibre

conventional opt. fibre

Peak

fluorescent opt. fibre

Plate

Rd

PC

LWL

M

ST

CC

VP

PRW

IEC 270

optical system

Oscilloscope,

ADU

Signal-conversion

Voltage supply

M. Muhr

IEC 62478

Test arrangement for optical PD-measurement

Optical – PD-Detection in GISOptical – PD-Detection in GIS

Emission spectrum of corona discharges in SF6

340 450 560 670 780 nm 340 450 560 670 780 nm 340 450 560 670 780 nm

SF6

Photomultiplier

Conv.PD Detector

ADU

I/U

Oscilloscope

M. Muhr

IEC 62478

SF6

Higher temperatures

Arc Partial discharge

decomposition

fluoric compounds (Fluoride)Sulfur-compounds (Sulfate, Sulfide)

Sulfur- fluoric-compounds

Chemical – PD-MeasurementChemical – PD-Measurement

Sensors and analyser

- H2 Sensor

- DGA (Gas in oil analysis)- Ozone analysis- Gas Analysis

M. Muhr

IEC 62478

• PD partial discharges • T1 temperatures T < 300° C

• D1 discharges with low energy • T2 temperatures 300° C < T < 700° C

• D2 discharges with high energy • T3 temperatures T > 700° C

Fehlerart 42

22

HC

HC

2

4

H

CH

62

42

HC

HC

PD - <0,1 <0,2 D1 >1 0,1 – 0,5 >1 D2 0,6 – 2,5 0,1 – 1 >2 T1 - >1 <1

T2 <0,1 >1 1 – 4

T3 <0,2 >1 > 4

Fehlerart 42

22

HC

HC

2

4

H

CH

62

42

HC

HC

PD - <0,1 <0,2 D1 >1 0,1 – 0,5 >1 D2 0,6 – 2,5 0,1 – 1 >2 T1 - >1 <1

T2 <0,1 >1 1 – 4

T3 <0,2 >1 > 4

IEC DGA Gas ratio values

Chemical – PD-MeasurementChemical – PD-Measurement

M. Muhr

IEC 62478

HF / VHF – PD-MeasurementHF / VHF – PD-Measurement

HF / VHF – Partial Discharge Detection

• Frequency range 3 MHz to 300 MHz

- HF 3 – 30 MHz- VHF 30 – 300 MHz

• Measuring systems

- Narrow-band, band width < 2 MHz- Wide-band, band width > 50 MHz

• Sensors

- Capacitive, inductive, electromagnetic

M. Muhr

IEC 62478

Measuring for HF – PD-detection on machines, VHF – PD-coupler, Split ring Rogowski coil

Rogowski coil

PD Analyser

HF / VHF – PD-MeasurementHF / VHF – PD-Measurement

Rogowski coil

M. Muhr

IEC 62478

HF / VHF HF / VHF –– PD-Measurement PD-Measurement

Principle of the coupler sensor

2

1

3direct. coupling A B

direct. coupling C D

impulsesource / - No.

signal at coupling output

A B C D

joint /1 – X X –

left cable / 2 X – X –

right cable / 3 – X – X

M. Muhr

IEC 62478

BA

C-Sensor

LDP-5

HF / VHF – PD-Signal DampingHF / VHF – PD-Signal Damping

Damping effects:

- Geometric proportions- Discontinuities- Impulse form- Refraction- Reflection- Frequency- Material

M. Muhr

IEC 62478

UHF – PD-MeasurementUHF – PD-Measurement

UHF – Partial Discharge Detection

• Transient electromagnetic waves

• Frequency range 300 MHz to 3 GHz

• Narrow band (~ 5 MHz)

• Wide band (~ 2 GHz)

• Propagation : - TM Wave (Transversal magnetic wave) - TE Wave (Transversal electric wave) - TEM Wave

• Not coupled to the conductor

M. Muhr

IEC 62478

UHF – PD-measurement

low-pass filter Peak detector

PD measuring instrument

PRPD pattern

Wide bandNarrow band

Spectrum analyser

amplifiers

UHF – PD-MeasurementUHF – PD-Measurement

M. Muhr

IEC 62478

UHF – PD-SensorsUHF – PD-Sensors

- Mobile UHF-window sensor

- Conventional UHF-sensors

Disc sensor Cone sensor

Conductor

Cage

Dectector

Field grading electrodes

Conductor

Cage

Detector

M. Muhr

IEC 62478

Sensitivity VerificationSensitivity Verification

UHF measurement

C1 C2

Signal 1

Defect

UHF measurement

PG

C1 C2

Signal 2

Impulses of variable

amplitude

M. Muhr

IEC 62478

UHF – PD-Fault LocationUHF – PD-Fault Location

L1

Schematic arrangement

Sensor 1

Pre amplifier

Measuring instrument

L2

Sensor 2

1 ... Sensor 12 ... Sensor 2

Time delay

Zeit

Am

pli

tud

e

1

2

Defect

M. Muhr

IEC 62478

Sensitivity of developed UHF-sensors

UHF – PD-Signal Damping, SensitivityUHF – PD-Signal Damping, Sensitivity

Damping effects:

- Frequency- Geometries- Conductor material- Mode type- Reflection and refraction

Sensivity:

- Facility configuration- Failure location- Location of the sensor - Measurement equipment

M. Muhr

IEC 62478

Principle schematic to the acoustic PD-detection

Acoustic – PD-MeasurementAcoustic – PD-Measurement

Acoustic Partial Discharge Detection

- Acoustic signal as a result of the pressure wave produced by PD- Frequency spectrum 10 Hz up to 300 kHz

SF6

Air

Box

AE Sensor

M. Muhr

IEC 62478

Acoustic – PD-SensorsAcoustic – PD-Sensors

HV

Time delay

SensorPD

Time

Sig

na

l

Directional microphone

PD

HV

- Piezo-electric (sound emission) - Condenser microphones- Structure-born sound-resonance - Accelerometer- Opto-acoustic-sensor

M. Muhr

IEC 62478

Acoustic – PD-detection system

amplifierOscilloscope

AE SensorPD-Detector

Filter

A/D Converter

Acoustic – PD-MeasurementAcoustic – PD-Measurement

M. Muhr

IEC 62478

Acoustic – PD-MeasurementAcoustic – PD-Measurement

Damping effects:

- Equipment dispersion- Construction- Insulation structures- Gas pressure- Encapsulation material- Absorption during a

medium to another- Geometrical spreading

of the wave

Acoustic fingerprint of a overhead line conductor

M. Muhr

IEC 62478

Experimental setup of the optical interferometric detection of PD

Opto-Acoustic – PD-MeasurementOpto-Acoustic – PD-Measurement

Laser

Reference optical fibre coil

Sensing optical fibre coil

Oil tank

High Voltage

PD-source

Detector

Beam Splitter

Beam Splitter

M. Muhr

IEC 62478

IEC TC42 WG 14IEC TC42 WG 14

Content 1

- Scope

- Phenomena• PD occurrence in discharging defects• Frequency / time behaviour• Specifies of HV-components• Applicability for detection

- Normative References

- Definitions

- Sensors• Types, parameters, positioning

- Location (time and frequency domain) vs measurement only

M. Muhr

IEC 62478

IEC TC42 WG 14IEC TC42 WG 14

Content 2

- Transmission Aspects

A) UHF Aspects

• PD source, quantity E [V/m]spectrum, filed mode, signal strength, magnitude, characteristic impedance, velocity of medium, distance, activity

• Sensor-antenna, basic quantity [m]type, bandwidth, position, receiving area, transfer impedance, characteristics

• Reading quantity [V]

• Derived quantitymeasuring equipment, bandwidth, center frequency, tuning

M. Muhr

IEC 62478

IEC TC42 WG 14IEC TC42 WG 14

Content 3

B) HF / VHF Aspects

• PD source, quantity [V] or [A]electric or magnetic signal, impedance, signal magnitude, distance, activity

• Sensor – impedance [R, L, C]type, bandwidth, position, dielectric attenuation, distortion, polarity aspects

• Reading quantity [V, A]

• Derived quantitymeasuring equipment, center frequency, tuning, bandwidth, pulse resolution

M. Muhr

IEC 62478

IEC TC42 WG 14IEC TC42 WG 14

Content 4

C) Acoustic Aspects

• Mechanical pressure, quantity [Pascal]pressure waves, modes, acoustic impedance, delay, propagation velocity, distance

• Sensor – impedancepiezo electric, composite material, optical, microphone, directivity, position, coupling, bandwidth, linearity

• Reading quantity [V]

• Derived quantitymeasuring equipment, pulse counter, pulse pattern

M. Muhr

IEC 62478

IEC TC42 WG 14IEC TC42 WG 14

Content 5

- System Checks

Performance and sensitivity check• UHF Aspects

performance check: functional check of the whole measuring path including sensor and PD acquisition systemsensitivity check: emission of electromagnetic waves into test objects, distance

• HF / VHF Aspectsperformance check: sensor to sensor coupling in a specific arrangementsensitivity check: injection of field signal to test object, distance

• Acoustic Aspectsperformance and sensitivity check: recommendation of acoustic standards

M. Muhr

IEC 62478

IEC TC42 WG 14IEC TC42 WG 14

Content 6

- pC Correlation• HF / VHF / UHF – pulse generator injection to determine relation

between pC and measured quantities• Acoustic: can not compared to pC without knowing the type of PD

source

- New quantities• parameters linear with sensor output [mV]• parameters quadratic with sensor output [mW]• effective height [mm] – ratio between sensor output and incoming

electrical field• Effective aperture [mm2] – ratio between maximum sensor output

power and power density of incoming electrical field• sensor gain [dBi] – ratio between receiving power antenna and

receiving power of isotropic radiator

M. Muhr

IEC 62478

IEC TC42 WG 14IEC TC42 WG 14

Content 7

EM – PD SourceBasic Quantity E [Volt / meter]

Sensor – AntennaBasic Quantity e.g.

[meter]

ReadingQuantity

[Volt]

PD [pC]

Quantity [m Watt]

Low Standard DeviationDefinition of Transfer Characteristic

Definition of TransferCharacteristic

Low Standard Deviation

System Check

Physical Generic Aspect

MathematicalTerm

Quantity [Volt]PD [pC]High Standard Deviation

M. Muhr

IEC 62478

IEC TC42 WG 14IEC TC42 WG 14

Content 8

Non Standardization

- Applicable sensor

- Test and measuring configurations

- Interpretation – task of the component panels

M. Muhr

IEC 62478

Thank You for Your Attention Thank You for Your Attention