Developments in Diagnosis of High Voltage Apparatus Michael Muhr Univ.-Prof. Dipl.-Ing. Dr.techn....

Developments in DiagnosisDevelopments in Diagnosisof High Voltage Apparatusof High Voltage Apparatus

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

Institute of High Voltage Engineering and System ManagementInstitute of High Voltage Engineering and System Management

MonitoringRecording of technical

or characteristic values

Evaluation of

these values

Recognition of the condition and

proposal for problem-solving strategies

Analysis

Diagnosis

M. Muhr


Technical Diagnostics - TDTechnical Diagnostics - TD

- Science of recognition of the condition of technical systems

- Aim of TD is to identify, to check and to classify characteristics of the condition of technical systems to change or to influence the condition of these systems

- Quality assurance of technical systems

- Avoidance of an outage of technical systems

M. Muhr


Technical Diagnostic

+ Prevent failure

+ Increase reliability

+ Economic use of equipment

Optimized usage of diagnostic tools

• Technique / method

• Time interval

• Complexity

- Costs

- Effort

- System

M. Muhr


Availability of technical systems

Condition evaluation

Risk evaluation

Technical Diagnostics

MaintenanceRepair Modernization

M. Muhr


Life Life CycleCycle

Lifetime

Condition

„normal“ defect

criticalthreshold

load

pollution

ageing

t

„lifetime extention"by

maintenance

failure

M. Muhr


Stress and Ageing ModelsStress and Ageing Models

M. Muhr


Lifetime Estimation of TransformersLifetime Estimation of Transformers

M. Muhr


Technical Diagnostic EvaluationTechnical Diagnostic Evaluation

Section 1

Section 2

Section 3

100

100

I

C

CO

CR

O

1

4

2 3

5

C ... Condition of the equipmentI ... Importance of the equipmentO ... Equipment 1, 2, 3, 4, 5

M. Muhr


Aim of TDAim of TD

Current condition

Modernization

Original condition

- Monitoring

- Analysis

- Diagnosis

- Preventive maintenance

- Repair

Original condition with ageing

- Ageing behaviour

- Life time

M. Muhr


Tasks of TD

Decision- Continuation of operation- Maintenance- Renewing

Monitoring of equipment Investigations at equipment and models

Life-time behaviourCharacteristic values, current, voltage etc.

Determining of limits Setting of continuous voltage strength

Optimization of life-time

M. Muhr


Bathtub Curve: from statistical analysis

1

6363

D

D

D t

t

t

<1: early failure

=1: stochastic process

>1: ageing process

Weibull Distribution:

Determination of Early FailuresDetermination of Early Failures

M. Muhr


Ageing of an electrical insulation system

Ageing mechanism• Instrinic• Exstrinic• Single stress• Multi stress

Electrical insulation system

Failure

Ageing stress• Thermal• Electrical• Ambient• Mechanical

M. Muhr


TD at equipment of electrical power engineering

Partial discharge diagnostic• Ue

• Q (pd)• φ (pd)

Thermal diagnostic• Thermovision• Temperature measurement

Mechanical diagnostic• Sound emission analysis• Dilatometry• Mechanical spectrometry• Analysis of mechanical quantities

Dielectric diagnostic• Ue

• u(t)•

C(f)• tan δ(f)

Analytic and spectrometry• UV, VIS, IR - Spectrometry• Gaschromatography• Mass spectrometry

Visual diagnostic• UV - Videography• Thermography• Endoscopy• X-ray graphy

Breakdown diagnostic• Ud

• φ (Ud)• t (Ud)

M. Muhr


Maintenance Strategies - LifetimeMaintenance Strategies - Lifetime

M. Muhr


Blockdiagramm of a Diagnosis SystemBlockdiagramm of a Diagnosis System

Reference components

Excitation• Measuring voltage• Measuring temperature

Control• Voltage• Temperature

Assessment and control unit• Storage of quantities• Run-off control• Data processing

• Input and Presentation• Further processing• Interface

Diagnosis sample• Original• Mode

Data acquisition - Sensors

Stress generation• Voltage• Temperature• Vibrations• Climate

M. Muhr


Non – Destructive TD at Power ApparatusNon – Destructive TD at Power Apparatus

Power apparatus

•Cables

•Solid switchgears

•Capacities •Transformers

•Instrument-transformers

•Rotating machines

•Insulators

•Conventional switchgears

•Circuit breaker

•Gasinsulated switchgears

•Dielectric diagnostic

•Visual TD

•Pd-diagnostic

•Sound emission diagnostic


•Visual TD

•Pd-diagnostic


•Gas analysis


•Visual TD

•Pd-diagnostic


•TD of mechanical quantities


•Visual TD

•Pd-diagnostic


•Leakage current diagnostic

•Visual TD

•TD of thermal and mechanical quantities

•Pd-diagnostic

•Leakage current diagnostic

•Visual TDTD of thermal quantities •Sound emission diagnostic

•Pd-diagnostic

M. Muhr


Basis Aspects of TDBasis Aspects of TD

- Aim

- Technique

- Method

- Quantity

- Connection between quantity and physical / chemical / technical structure of diagnostic sample

- Diagnostic criterion - limit

M. Muhr


Technical DiagnosticTechnical Diagnostic

Thermal

Mechanical

Dielectrical

Partial Discharge

Breakdown

Material analytic

and Spectrometry

Mea

ning

fuln

ess

(str

ess)

Non-destructive

individual testing

Quasi non-destructive

Partly individual testing

Destructive

Type approval test

Random check

M. Muhr


Electrical Diagnostic MethodsElectrical Diagnostic Methods

Partial Discharge

Breakdown

Dielectric

M. Muhr


• Insulation Resistance

• Capacity and Dissipation Factor

• Isothermal Relaxation Current Analysis (IRC)

• Polarisation / Depolarisation Current Analysis (PDC)

• Frequency Response Analysis (FRA)

Observation and evaluation of interaction of electric fields and material

Dielectric DiagnosticsDielectric Diagnostics

M. Muhr


U=

I

RS

RO

RD

U=

I

RS

RO

RD

Insulations Resistance Surface Resistance

Insulation ResistanceInsulation Resistance

Guard Ring Arrangement

M. Muhr


Capacity and Dissipation FactorCapacity and Dissipation Factor

CX

RX

CN

PC

DSP

AD

AD

CX

RX

CN

R3 R4 CN

HV

M. Muhr


Analyse in Time DomainAnalyse in Time Domain

V AA

Disch

arg

e V

olta

ge

An

alyse

Disch

arg

e C

urre

nt A

na

lyse

Re

cove

ry Vo

ltag

e A

na

lyse

Ch

arg

ing

curre

nt A

na

lyse0%

20%

40%

60%

80%

100%

120%

PDCIRCPDC RVM

curr

en

tvo

ltag

eSchema

M. Muhr


Isothermal Relaxation Current Analysis (IRC) Isothermal Relaxation Current Analysis (IRC)

V AA

Schema

M. Muhr


Polarisation / Depolarisation Current Analysis (PDC)Polarisation / Depolarisation Current Analysis (PDC)

V AAPolarisation

Depolarisation

Time

Schema

M. Muhr


Frequency Response Analysis (FRA)Frequency Response Analysis (FRA)

U, I U, I

HV LV

0.0001

0.001

0.01

0.1

1

10 100 1000frequency [kHz]

In/O

ut

normal

defect

M. Muhr


Breakdown DiagnosticBreakdown Diagnostic

HV-AC

96

98

100

102

104

106

108

1 6 11 16 21 26 31 36 41 46 51

Attempt

Vo

ltag

e [k

V]

Voltage [kV]96 98 100 102 104 106 108

Pro

babi

lity

[%]

12

510

2030

50

7080

9095

9899

M. Muhr


Breakdown Test with Insulating Oil Breakdown Test with Insulating Oil

0

20

40

60

80

100

1 2 3 4 5 6test series

mea

n va

lue

(kV

)

0

20

40

60

80

100

coef

ficie

nt o

f var

iatio

n (%

)

0.5kV/s mean value 0.5kV/s coeff. of variation2kV/s mean value 2kV/s coeff. of variation5kV/s mean value 5kV/s coeff. of variation

M. Muhr


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


Partial Discharge DiagnosticPartial Discharge Diagnostic

Optical

Electrical

Mechanical

Chemical

IEC 60270

HF/VHF/UHF

Acoustic

Opto-acoustic

HV

M. Muhr


• Conventional electrical measurement

• Integration at frequency domain

• Narrow-band

• Wide-band

• Integration at time domain

G

ZFilter

HV-Source

Test object

Coupling capacitor

PD-System

HVmeasure

PDPulse

QuadripoleMeasuring impedance

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

M. Muhr


PD-Measurement ResultsPD-Measurement Results

Phase correlated

Single impulses

Time correlated

M. Muhr


PDC AnalysePDC Analyse

M. Muhr


Unconventional PD-DetectionUnconventional PD-Detection

Rd

ST

CC

VP

W

Rd

ST

CC

W

RPA1

HST1

AMP

SYNC

ICM

LWL

Signal-conversion

acoustic

optical

Oscilloscope

ADU

electrical Surface

Fibre in oil/board

LWL fibre

M. Muhr


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


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

measurement impedance

cable

HV source

PD-signal

inductive

galvanic

PD-signal

current

wire sheath

cable cable

PD-signal

Rogowski coil

PD-signal

sheath interruption

measurement impedance

cable

M. Muhr


Rogowski coil

PD Analyser

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

Rogowski coil

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

M. Muhr


Principle of the coupler sensor

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

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


low-pass filter Peak detector

PD measuring instrument

PRPD pattern

Wide bandNarrow band

Spectrum analyser

amplifiers

UHF – PD-measurement

UHF – PD-MeasurementUHF – PD-Measurement

M. Muhr


- Mobile UHF-window sensor

- Conventional UHF-sensors

Disc sensor Cone sensor

Conductor

Cage

Dectector

Field grading electrodes

UHF – PD-SensorsUHF – PD-Sensors

Conductor

Cage

Detector

M. Muhr


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

UHF – PD-Fault LocationUHF – PD-Fault Location

Defect

M. Muhr


SF6

Air

Box

AE Sensor

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

Principle schematic to the acoustic PD-detection

M. Muhr


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


amplifierOscilloscope

AE SensorPD-Detector

Filter

A/D Converter

Acoustic – PD-detection system

Acoustic – PD-MeasurementAcoustic – PD-Measurement

M. Muhr


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


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

PD – Optical DetectionPD – Optical Detection

Rd

PC

LWL

M

ST

CC

VP

PRW

IEC 270

optical system

Oscilloscope,

ADU

Signal-conversion

Voltage supply

M. Muhr


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

Test arrangement for optical PD-measurement

SF6

Photomultiplier

Conv.PD Detector

ADU

I/U

Oscilloscope

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

M. Muhr


Operation diagram camera DayCor IITM and application

Optical – PD-MeasurementOptical – PD-Measurement

M. Muhr


PD – ApplicationPD – Application

UHF- GIS- GIL- Transformer monitoring

HF / VHF- High voltage cables- Transformers

Acoustic- High voltage cables- GIS- Transformers- Overhead lines

Optical- GIS- Overhead lines

Chemical- GIS- Transformer- Machines

Electrical-Transformers- GIS- Machines - GIS- Overhead lines- ...

M. Muhr


Data input and

monitoring unit

ReportDisplayData archiving Real time

announcementAlarm Data transfer Trend analysis

ModemTelephone lines PC station

Monitoring, Data Processing, AnnouncementMonitoring, Data Processing, Announcement

M. Muhr


Signal processing

ReportDisplay Data store Data transfer Trend analysis

Example for signal processing

Pattern RecognitionPattern Recognition

M. Muhr


PD-Evaluation

Loss Factor

Insulation Resistance

FRA-Analysis

PD Location

Partial Discharges

Insulation

Signal Analysis

Transfer Function

Wavelet Technique

RVM, FDS Analysis

Endoscopy

Dynamics

Oil Stream

Transient Oil Pressure

UHF PD-Detection

Operating Noises

Acoustics

Oil Analysis

Moisture

Furane Values

IEC 599

IEEE C57.1041991

Dörnenburg

Rogers

Duval

Other Methods

Dissolved Gas Analyses (DGA)

Neutralization Value

Elektrisch

Mechanisch

Thermisch

ElectricalOptical

Mechanical

Chemical

Thermal

Thermography

Temperature Monitoring

Operating Temperature

Eye

PDC-Analysis

Fibre Optics Loss Factor

Breakdown VoltageOil Analysis

DAC-PD-Measurement

Power Transformer DiagnosticsPower Transformer Diagnostics

M. Muhr


Method Information Comment

Oil analysis OA Oil ageing, insulation property Routine

Gas-in-oil analysis DGAOil and paper ageing, flashovers, PD,

hot spotsRoutine

Loss factor (Dielectric dissipation factor)

tanδ Dielectric losses in the insulation system Routine

Furane values FA Ageing of the paper insulation Condition determination

Degree of polymerization

DP Ageing of the paper insulation Condition determination

Partial discharges PDPaper ageing, ageing of the

insulation systemCondition determination

Polarisation anddepolarisation

currentsPDC Water content in the paper insulation Condition determination

Infraredmeasurements

IR Overload, failure of the cooling systemCondition determination

and for fault location

Acousticmeasurements

AM PD-detection and location For fault location

Frequency response FRA Mechanical condition of the windings After short circuits

M. Muhr


Bre

akd

ow

n v

olta

ge

[kV

]

Water content [ppm]

dilution emulsion

tief

hoch

tief

hoch

Water content in oil

Wa

ter

con

ten

t in

pa

pe

r

Temperature

High

Low

Moisture

• Karl-Fischer titration

• Capacitive sensors

• Breakdown voltage

• PDC

Oil AnalysisOil Analysis

M. Muhr


Loss Factor (tanδ)

• Heat losses are temperature-dependent

• High loss factor – thermal breakdown

• Limit: tanδ ≤ 5 %by T=100° C

Temperature dependace of tanδ for new oil (1) and oils in operation (2,3,4)


M. Muhr


Dissolved Gas Analysis (DGA)

• Key gases: hydrogen, methane, ethane, ethylene, acetylene, propane, propylene, carbon monoxide, carbon dioxide

• Detectable failures: thermal and electrical failure


M. Muhr



DGA - Evaluation

• CIGRE

• IEC

• IEEE

• Dörnenburg

• MSS / VDE-Diagnosis

• Rogers

• Duval

• Laborelec

• KEPCO

Duval triangel

M. Muhr


Paper AnalysisPaper Analysis

Polymerisation degree (DP)

- In direct correlation with the mechanical strength

new paper DP 1000 – 1200

paper at the end of life time DP approx.200

- A decrease in the DP value furane is going hand in hand with an increase of components

- Furane dependence

• Oil temperature • Type of oil

• Neutralization factor • Type of paper

• Sludge content • Moisture content of oil and paper

• Ratio oil / paper

M. Muhr


Furane Analysis

• Condition of paper insulation (mechanical strength) determined by degree of polymerization

• High performance liquid chromatograph (HPLC)


M. Muhr


• Conventional

• Acoustic

• Optical

• Chemical

• Electrical

• New Systems: electromagnetic wave detection,transfer functions, damped AC voltage (DAC)

Partial DischargesPartial Discharges

Measurementin laboratory

conventionalmeasurement

IEC 60270Acoustic

PD - measurement

OpticalPD - measurement

ChemicalPD – measurement

(DGA)

electricalHigh frequency

PD - measurement

Narrow bandΔf ~ 10 kHz

Broadband Δf ~ 50 - 500 kHz

HF/UHFmethod

f ~ 10 - 500 kHz

Narrow bandΔf < 2 MHz

Measurementon-site

UHFmethod

f ~ 0,2 - 2 GHz

BroadbandΔf > 50 MHz

M. Muhr


Dielectric DiagnosisDielectric Diagnosis

Charging and discharging measurements

M. Muhr


Diagnostics with Transient Test VoltagesDiagnostics with Transient Test Voltages

• Frequency response analysis (FRA) and transfer function

• Low voltage impulse response (LVI)

• Wavelet analyse

• DAC-PD-measurement

FRA

M. Muhr


Thermal and Optical Diagnostic MethodsThermal and Optical Diagnostic Methods• Thermography

• Temperature measurement with fibre optics

• PT-100 elements

• Surface acoustic wave radio transponder

• Visual inspection

• Endoscopy

OKULAR

LICHTQUELLEFLEXIBLES ENDE

BLICKBEREICH

Ocular

Light source Flexible end

Field of vision

M. Muhr


Mechanical Diagnostic MethodsMechanical Diagnostic Methods• Transient oil pressure (short circuit)

• Stream analysis (oil and cooling air)

• Acoustic PD-locating

StreamNostream

M. Muhr


Diagnosis of Rotating MachinesDiagnosis of Rotating Machines

Tasks • Thermal monitoring

• Air cooling analysis

• Monitoring of vibrations

• Acoustic monitoring

• Chemical-analytic monitoring

• Magnetic monitoring

• Electrical monitoring

M. Muhr


Rotating MachinesRotating Machines- Electrical Diagnosis Methods

• Impulse voltage test at windings

L

R

2

SCL.

1

teUtu t cos.. .

Attenuation factor

Resonance frequency of resonating circuit

tu - Oscillogram of a decaying oscillation

a) Error –free

b) faulty

M. Muhr


Rotating MachinesRotating Machines

- Dielectric Diagnosis

• Time domain

- Insulation resistance Riso

- Insulation current iiso = f (t)

• Frequency domain

- Capacitance

- Loss factor tan = f (), C, U

M. Muhr


(1) Dry condition(2) Humid condition(3) Dryness limit curve

Cooling

Heating


- Dielectric Diagnosis

Insulation time constant 10 as criterion for the dryness limit curve 10 = Riso (600s) x C (50Hz)

10 = f ()

Insulation time constant in dependance of the slot temperature and the insulation condition

M. Muhr



- Partial discharge (Pd) diagnosis

• Pd’s

- In cavities of solid insulation

- In the are of the end winding

- At no-perfect working protect system of mica

- At vibrating parts of winding

M. Muhr


Physical Condition of WindingsPhysical Condition of Windings

M. Muhr


Discharge behaviour within Machine WindingsDischarge behaviour within Machine Windings

M. Muhr


Thermography as Diagnostic ToolThermography as Diagnostic Tool

• Requirement

- Increasing efficiency of power grid

- Decreasing of inspection and maintenance rate

• Load situation

- Increasing electrical power consumption

- Higher loads on equipment

• Demand of ON-line diagnostic tools

E.g. Contact less temperature measurement

M. Muhr


Thermography as Diagnostic ToolThermography as Diagnostic Tool

Material/Structure

Heat GenerationTemperature

Surface temperature

Surface tem

perature

Surface temperature

power output

powe

r outpu

t

power outputSurrounding

• Load currentResistor

• VoltageConductivityDielectric losses

Temperaturemeasurement

M. Muhr


Isolated Transmission

Temperature MeasurementTemperature Measurement

High Voltage

ObjectTemperature

SensorCoupling SignallingTransmissionpower supply

Isolated Coupling

High Voltage

ObjectTemperature

SensorCoupling SignallingTransmissionpower supply

M. Muhr


Spot Temperature MeasurementSpot Temperature Measurement

Transformer

29.8°C29.7°C29.8°C29.6°C29.7°C29.9°C29.8°C29.7°C29.6°C29.5°C30.0°C29.7°C29.9°C29.7°C29.7°C30.1°C29.9°C29.9°C29.7°C29.8°C30.0°C30.0°C30.0°C29.9°C29.8°C

M. Muhr


Temperature DistributionTemperature Distribution

Hot

Cold

33°C 23°C

M. Muhr


Thermography in HV - SystemsThermography in HV - Systems

- Applications

• Connections

• Switches

• Power transformers

• Measuring transformers

• Overhead lines

• Cable terminations

• Bushings

• Fuses

• Rotating Machines

M. Muhr


Applications of ThermographyApplications of Thermography

Poor contact resistance of a joint

Poor contact resistance of a disconnector

M. Muhr



Compression connector of an overhead line

Asymmetrical energy flow of a cable

M. Muhr


Thank You for Your Attention Thank You for Your Attention

Developments in Diagnosis of High Voltage Apparatus Michael Muhr Univ.-Prof. Dipl.-Ing. Dr.techn....

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Transcript of Developments in Diagnosis of High Voltage Apparatus Michael Muhr Univ.-Prof. Dipl.-Ing. Dr.techn....