Medida de Descargas Parciais Omicron

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    iagnostic Measurements on Powerransformers

    Michael Krger e Marcelo Paulino - Soaulo maio/2010 1

    INTRODUCTION INTO PARTIAL DISCHARGE (PD)PHENOMENA AND PD MEASUREMENT

    Dr. Michael Krger

    May 10 PAGE 2

    Introduction

    Partial Discharges (PD)

    "localized electrical discharges that only partially

    bridge the insulation between conductors" [IEC 60270:2000]

    can harm insulation systems generate electromagnetic signals

    PD Measurement

    General specifications: IEC 60270:2000o Transformers: IEC 60076 (and others)

    detection of critical defects

    recognition of defects

    assessment of risk

    measurable

    May 10 PAGE 3

    PD Inception and Extinction Voltage

    Internal PD hashystersis

    External coronahas normally nohysteresis

    IEC 60034-27

    May 10 PAGE 4

    PD Classification

    a) corona discharge b) surface discharges

    c) discharge in laminated material d) cavity discharge

    e) treeing

    May 10 PAGE 5

    Electrical Treeing in PE

    May 10 PAGE 6

    Electrical Treeing in PE

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    May 10 PAGE 7

    Chemical (DGA)

    Optical (e.g. UV camera for corona)

    Electrical (narrow band or wide band)according to IEC 60270

    Acoustical

    UHF

    Detection of PD

    May 10 PAGE 8

    Equivalent Circuit Diagram

    Uz

    U1(t)

    Ut(t)

    U'1(t)-Uz

    tUL-UL

    FCUq .1=

    I1(t)

    t

    B

    A

    CP

    CS

    CF

    R1

    SI1(t)

    Ut

    U1

    Is(t)

    I2(t)I3(t)

    B

    A

    r0CP/2 CP/2

    2CS

    2CS

    CF

    = dttiq ).(1

    May 10 PAGE 9

    Apparent Charge

    Apparent charge q, of a pulse is that charge

    which, if injected between the terminals of the

    test object, would give the same reading on

    the measuring instrument as the PD current

    pulse itself.

    Expressed usually in pC.

    The apparent charge is not equal to theamount of charge locally involved at the site

    of the discharge, which can not measured

    directly.

    May 10 PAGE 10

    When to measure?

    Factory test:

    Standard measurement during the AC withstand testfor every new (or repaired) transformer. Usually lowground noise level.

    On-site test:

    After indication of DGA results.

    Usually high ground noise level and other disturbances.

    May 10 PAGE 11

    The classical visualization

    May 10 PAGE 12

    PRPD Phase Resolved Histogram

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    May 10 PAGE 13

    Calibration of the PD Instrument

    CK

    Z

    CtU ~A

    B

    I(t)

    U0

    C0

    Calibrator

    Cc

    ZmUmMeasuringImpedanc

    e

    M

    Amp. Filter

    qks .max

    =

    Smax

    Q = C * U

    May 10 PAGE 14

    Transformerunder test

    Couplingcapacitor

    Conventional Coupling of the MeasuringDevice

    Testingtransformer

    IPD

    PD

    Fault (discharge)

    May 10 PAGE 15

    Typical PD Measurement in a Test Lab

    Testing transformer

    Test object

    Coupling capacitor

    Faraday cage

    PD instrument

    May 10 PAGE 16

    NoiseFiltering

    - High bandwidth desirable for sensitive measurement andhigh pulse repetition rates

    - Low bandwidth improves interference rejection

    - Always use the highest possible bandwidth

    - Only a variable filter is suitable for on-site measurements

    May 10 Page: 17

    Analogue and Digital PD measuring instruments

    PD systems

    Analogue PD measuringinstrument

    May 10 PAGE 18

    Traditional PD Measurement

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    May 10 PAGE 19

    "Digital" PD Measurement withAnalogue Filter

    May 10 PAGE 20

    "Digital" PD Measurement with Multi-Channels and MUX

    May 10 PAGE 22

    MPD 600 True Digital Measurement withDigital Filtering

    May 10 Page: 24

    Synchronous Multi-Channel PD MeasurementSystem MPD600

    May 10 PAGE 26

    Synchronous multi-channel

    measurement

    May 10 PAGE 27

    Separation of PD and Corona Sources at

    Different Locations with 3PARD

    3PARD = Three Phase Amplitude Relation Diagram

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    May 10 PAGE 28

    Inner PD source in L1 in 3PARD

    L1

    L2

    L3

    L1

    L2

    L3

    Inner PD SourceL1>L2>L3

    3PARD

    timeframe1 s

    Inner PD Source in

    L1

    5

    3PARD = Three Phase Amplitude Relation Diagram

    May 10 PAGE 29

    L2

    L3

    3PARD

    L1

    L1

    L2

    L3

    Outer NoiseL1 L2 L3

    timeframe1 s

    Outer Noise

    6

    Outer noise in 3PARD

    3PARD = Three Phase Amplitude Relation Diagram

    May 10 PAGE 30

    3PARD

    May 10 PAGE 31

    Back Transformation

    May 10 PAGE 32

    PD source 1 PD source 2 PD source 3

    FFT pulse 1

    FFT pulse 2

    FFT pulse 3

    FFT of all three impulses

    MPD600

    Frequency 2

    Frequency 1Frequency 3

    PD source 2

    PD source 3

    PD source 1Frequency 3F re qu en cy 1 F re qu en cy 2

    3CFRD 3 Center Frequency

    Relation Diagram

    May 10 PAGE 33

    Measurement at Three Different Frequencies

    with 3CFRD

    Faulty joint

    Needle

    Surfacedischarge

    22kV_Corona_Surface_Joint

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    Michael Krger e Marcelo Paulino - Soaulo maio/2010 6

    May 10 PAGE 34

    Case Studies

    PD Measurements on Power Transformers

    Coupling of the Measuring System

    May 10 PAGE 37

    Coupling of the PD Measurement Instrumentto the HV Bushing Measuring Tap

    MPD600

    May 10 PAGE 38

    Power Transformer 132kV/32kV inthe Factory

    May 10 PAGE 39

    PD Decoupling at the Measuring Tap ofthe HV Bushing

    May 10 PAGE 40

    PD Decoupling at the Measuring Tap

    of the HV Bushing

    Advantage

    Little constructive effort

    No coupling capacitors necessary

    Drawback

    Measuring tap not always

    accessible / existing

    May 10 PAGE 41

    PD Decoupling by Coupling

    Capacitors

    MPD600

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    May 10 PAGE 42

    PD Decoupling by CouplingCapacitors

    May 10 PAGE 43

    PD Decoupling by CouplingCapacitors

    May 10 PAGE 44

    HV Connections PD free!

    May 10 PAGE 45

    Inductive PD Decoupling at Cable Screen

    May 10 PAGE 46

    Capacitive Sensors

    Sensor for capacitive coupling(Patented by the University of Hannover)

    MPD 600

    MPD 600

    MPD 600

    May 10 PAGE 47

    Practical Examples

    PD Measurements on Power Transformers

    Measuring Results

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    Michael Krger e Marcelo Paulino - Soaulo maio/2010 8

    May 10 PAGE 48

    Measuring Results

    30 MVA Transformer, 115 kV / 11.3 kV

    May 10

    Page 49

    Synchronous Multi-Channel PD Measurementon a 30MVA 115 / 11.3 kV Transformer

    May 10 PAGE 50

    Decoupling of PD at the Neutral

    May 10 PAGE 51

    Measuring Results

    30 MVA Transformer, 115 kV / 11.3 kV

    Statistical Noise

    External Disturbance

    PD Fault

    May 10

    Page 52

    Transformer with Coupling Capacitors,

    Step-up Transformer and Diesel Generator

    Coupling capacitorwith MPD 600 on U

    Step-up transformer400V / 21kV

    DieselGenerator

    Transformer

    UVW

    May 10

    Page 53

    Simultaneous PD Measurement on

    3 Phases

    without 3PARDfiltering

    with3PARD

    filtering

    U

    V

    W

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    Michael Krger e Marcelo Paulino - Soaulo maio/2010 9

    May 10

    Page 54

    PD source 1 PD source 2 PD source 3

    FFT pulse 1

    FFT pulse 2

    FFT pulse 3

    FFT of all three impulses

    MPD600

    Frequency 2

    Frequency 1Frequency 3

    PD source 2

    PD source 3

    PD source 1Frequency 3F re qu en cy 1 F re qu en cy 2

    3CFRD 3 Center FrequencyRelation Diagram

    May 10

    Page 55

    Simultaneous PD Measurement at 3Different Center Frequencies, Phase U

    3MHz

    300kHz10MHz

    withoutfiltering

    withfiltering

    3MHz

    300kHz

    10MHz

    May 10

    Page 56

    Decrease of the PD Amplidude withIncreasing Frequencies

    PD is not close to themeasurement point (bushing)

    10MHz3MHz

    May 10 PAGE 6114.05.2010OMICRON Energy Page 61

    Combined UHF and IEC Measurements

    May 10 PAGE 6214.05.2010OMICRON Energy Page 62

    Connection to

    the MeasuringTap of theBushing

    May 10 PAGE 6314.05.2010OMICRON Energy Page 63

    UHF Sensor at the Main Valve

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    May 10 PAGE 64

    The OMICRON mtronix Solution

    May 10 PAGE 65

    The OMICRON mtronix Solution

    May 10 PAGE 66

    Combined UHF and IEC measurement

    IEC PD Measurement UHF PD Measurement

    Corrected IEC PD Measurement

    +

    May 10 PAGE 67

    Summary

    Partial Discharges (PD) can lead to outages

    PD measurement is reasonable tool for

    diagnosis and quality control

    Sensitive PD measurements: High demands on

    PD measuring system

    MPD600: a variable tool for all kind of

    application electrical equipment (cable, transformer, rot.

    machines, )

    measuring condition (laboratory, factory, on-site)

    May 10 PAGE 68

    T

    hankYouforYourkind

    a

    ttention!