1 PD Training Fundamentals of Partial Discharge

Fundamentals of Partial Discharge Dipl.-Ing. Falk-Rüdiger Werner Doble Lemke, Germany [email protected]

Contents 1. Fundamentals 2. PD Measurement 3. PD Analysis 4. Doble Lemke PD Testing Solutions

Fundamentals of Partial Discharge

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1. Fundamentals Different types of discharges in HV insulations:  Complete breakdown:  Insulation breaks down completely  Electrodes are connected with low resistance

 Incomplete breakdown:  Insulation breaks down partially  “Healthy” part of the insulation is capable to withstand a breakdown  This type of breakdown is called „Partial Discharge“ (PD)


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1. Fundamentals Reasons for PD: local overstressing of insulation  Local raise of field strength (e.g. at conductive spikes)  Local reduction of dielectric strength (e.g. at gas filled cavities) Results in degradation / aging of the insulation system


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1. Fundamentals Partial Discharges in Gases:  Corona discharge  Sharp edges  Conductors with too small diameter  Sharp edged particles

 Surface discharges  Generally faced problem  Countermeasures

Sharp Edge

Thin Wire

Particle

Arrangements for Surface Discharges Glow discharges

[Küchler, 1996]

Streamer Discharges

• Capacitive potential grading at bushings • Geometric field grading at terminations • Prolongation of leakage distance and hydrophobic surfaces on insulators


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1. Fundamentals Defects in the dielectric causing PD: (solid insulation systems)

 Voids, cavities  Cracks  Delaminations Voids without (1) or

Cracks, Gaps and

with (2) electrode contact

uncompleted Layers

and delamination (3)

Delamination at staple

Cable with Termination

boundary surfaces

(1) Voids through treeing (2) Voids at boundary surface


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1. Fundamentals Defects in the dielectric causing PD: (liquid insulation systems)

 Small radii of curvatures (leads, spikes, conductive particles)  Gas generation (gas bubbles, gas layers)  Tangential overstraining of insulating material surfaces (pressboard barrier systems)

Sharp Edge

Particle

Voids (Gas Bubbles)

Arrangements for Surface Discharges in Oil

Gas Layers

Capacitor-Dielectrica with coat edge

Barrier Arrangement

Tangential stressed

with filament brigde

boundary surface

HV arrangements causing PD in oil-paper insulation systems Fundamentals of Partial Discharge

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1. Fundamentals PD Detection Principles

HV

Optical Effects (Light)

Optical

Pressure Wave (Sound)

Mechanical

Opto-acoustic

Discharge Effects Dielectric Losses High Frequency Waves

Electrical

IEC 60270

Acoustic

HF/VHF/UHF Chemical Effects

Chemical

Heat

All detection principles are based on the energy conversion during the discharge Fundamentals of Partial Discharge

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1. Fundamentals C1: Void Capacitance Is fully discharged when inception voltage Uz is reached C2 : Capacitance of sound insulation in series to Void C3 : Capacitance of sound insulation parallel to Void u1(t): Voltage in the void i(t): PD current

u10 t  

C2 u t  C1  C2


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2. PD Measurement 2.1 PD Measurement Methods Overview

PD Measurement Methods used by Doble Lemke Electrical Measurement acc. IEC 60270 • Coupling capacitor and measurement impedance • Broadband signal processing • Narrowband signal processing


Non-Conventional Measurement Procedures • Decoupling of the magnetic or electromagnetic field with appropriate sensors • Ultrasonic detection • Visible light and UV light detection • Chemical analysis (DGA)

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2. PD Measurement 2.2 History PD Measurement (DL)

Evolution of PD Measurement Charge: 20 pC/div, Time-Basis: 4 ms/div

Simply PD Detection by using a Oszilloscope

Analogue PD Detector

90s

Digital PD Detector

2000

Computer Technologies as milestone for the development of PD Detection systems


Fully Digital PD Detector

2010

Finalization the first generation of PD Monitoring System, PD Guard as PDM System established

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2. PD Measurement 2.3 IEC 60270 PD Measurements

IEC 60270 Standard Circuits DUT

Impedance in Series to Ck

Impedance in Series to Ca

Bridge Circuit

Bushing Capacitance


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2. PD Measurement 2.3 IEC 60270 PD Measurements

Blocking Impedance

Coupling Capacitor

Measurement Quadripole


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2. PD Measurement 2.4 Non Conventional PD Measurement Methods

Non-IEC PD Sensors

Acoustic • Ultrasonic transducers

UHF/VHF/RF • UHF antenna • UHF coupler • TEV Sensor • HFCT


Other • Capacitive coupling • Inductive coupling

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Acoustic PD Measurement:  Good for Location on Transformers  Rather Insensitive for Detection PD (partial discharge)

S 3 (x s3 , y s3 , z s3 ) Sound field (acoustic wave)

PiezoSensor

D3 S (x s4 , y4s4 , z s4 ) D2 D4 Si PD (x si , y si , z si ) Di (x, y, z) D1

S (x s22, y s2 , z s2 )

S1 (x s1, y s1, z s1 )

© Doble Lemke / University of Stuttgart


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Non Conventional PD Measurement (UHF)  Transformer  Drain Valve Sensor  Top Hatch Sensor

 GIS  Window Sensor  Spacer Sensor

 Cable  Termination Sensor


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C

D

B A E

A - PD site in the insulation B - Radiated electromagnetic field C - Voltage drop at the HV side D - Electric field via the stray capacitance to ground E - Magnetic field by the current in the ground lead


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2. PD Measurement 2.4 PD Analysis (IEC and VHF/UHF)


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3. PD Analysis


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3. PD Analysis Classification based on PD-Pattern:  Corona Discharge  Surface Discharge  Void Discharge


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3. PD Analysis 3.1 Corona Discharge

Corona Discharge


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3. PD Analysis 3.2 Surface Discharge

Surface Discharge


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3. PD Analysis 3.2 Void Discharge

Void Discharge


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4. Doble Lemke Solutions 4.1 Measurement Systems

Acoustic PD-Location •LDP-5/A •LDA-5 •LDA-6

IEC 60270

Non-Conventional

PD-Detection and Analysis •LDS-6 UHF •PD-Smart •PD-Guard PD-Detection and Analysis •LDS-6/UHF •PD-Smart/UHF •PD-Guard/UHF


Survey PD-Detection •LDP-5

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Doble Lemke PD Testing Solutions LDS-6

PD-Smart

IEC / UHF Measurement

IEC / UHF Measurement

Wideband (IEC)

Wideband (IEC)

Narrowband (IEC/UHF)

Narrowband (IEC/UHF)

Fault Location (Cables)

Fault Location (Cables)

Noise Gating

Noise Gating

Adjustable Input Filters 35kHz-20MHz Multi-Synchronous-Measurement Star Diagram Windowing

Rugged Chassis


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Any kind of DUT


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4. Doble Lemke Solutions 4.2 PD Measurement Sensors C-Sensor

Window-Sensor

UHF Coupler L-Sensor UHF Antenna IEC 60270 TEV-Sensor HFCT Acoustic


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1 PD Training Fundamentals of Partial Discharge

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