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

2


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

5


1. Fundamentals

Partial Discharges in Gases:

Corona discharge

Sharp edges

Conductors with too small

diameter

Sharp edged particles

Surface discharges

Generally faced problem

Countermeasures

• Capacitive potential grading at bushings

• Geometric field grading at terminations

• Prolongation of leakage distance and hydrophobic surfaces on

insulators

7

[Küchler, 1996]

Thin WireSharp Edge Particle

Glow discharges Streamer Discharges

Arrangements for Surface Discharges


1. Fundamentals

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

Voids, cavities

Cracks

Delaminations

8

Voids without (1) or

with (2) electrode contact

and delamination (3)

Cable with Termination

(1) Voids through treeing

(2) Voids at boundary surface

Cracks, Gaps and

uncompleted Layers

Delamination at staple

boundary surfaces


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)

9

HV arrangements causing PD in

oil-paper insulation systems

Particle

Voids

(Gas Bubbles)

Sharp Edge

Gas Layers

Barrier Arrangement

with filament brigde

Tangential stressed

boundary surface

Arrangements for

Surface Discharges in Oil

Capacitor-Dielectrica

with coat edge


1. Fundamentals

10

Optical

Mechanical

Chemical

Acoustic

Opto-acoustic

HV

Electrical IEC 60270

HF/VHF/UHF

Optical Effects

(Light)

Pressure Wave

(Sound)

Discharge Effects

Dielectric Losses

High Frequency

Waves

Chemical Effects

Heat

PD Detection Principles

All detection principles are based on the energy conversion

during the discharge


1. Fundamentals

11

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

tuCC

Ctu

21

210


2. PD Measurement

13

PD Measurement

Methods used by

Doble Lemke

Electrical Measurement acc.

IEC 60270

Non-Conventional

Measurement Procedures

• Coupling capacitor and

measurement impedance

• Broadband signal

processing

• Narrowband signal

processing

• Decoupling of the magnetic or

electromagnetic field with

appropriate sensors

• Ultrasonic detection

• Visible light and UV light detection

• Chemical analysis (DGA)

2.1 PD Measurement Methods Overview


2. PD Measurement

Evolution of PD Measurement

14

90s 2000 2010

Charge: 20 pC/div, Time-Basis: 4 ms/div

Analogue PD Detector Digital PD Detector Fully Digital PD DetectorSimply PD Detectionby using a Oszilloscope

Computer Technologiesas milestone for the developmentof PD Detection systems

Finalization the first generationof PD Monitoring System,PD Guard as PDM System established

2.2 History PD Measurement (DL)


2. PD Measurement

IEC 60270 Standard Circuits

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Impedance in Series to CkImpedance in Series to Ca

Bridge Circuit

Bushing Capacitance

2.3 IEC 60270 PD Measurements

DUT


2. PD Measurement

16

Blocking Impedance

Coupling Capacitor

Measurement Quadripole

2.3 IEC 60270 PD Measurements


2. PD Measurement2.4 Non Conventional PD Measurement Methods

Non-IEC PD Sensors

Acoustic

• Ultrasonic

transducers

UHF/VHF/RF

• UHF antenna

• UHF coupler

• TEV Sensor

• HFCT

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Other

• Capacitive coupling

• Inductive coupling


2. PD Measurement

18

2.4 Non Conventional PD Measurement Methods

Acoustic PD Measurement:

Good for Location on Transformers

Rather Insensitive for Detection

Sound field (acoustic

wave)

Piezo-

Sensor

PD (partial discharge)

)z ,y ,(x s1s1s11S

2S

)z ,y ,(x s3s3s33S

)z ,y ,(x s4s4s4

iS

4S

)z ,y ,(x s2s2s2

1D

2D3D

4D

iD)z ,y ,(x sisisi

PD(x, y, z)

)z ,y ,(x s1s1s11S

2S

)z ,y ,(x s3s3s33S

)z ,y ,(x s4s4s4

iS

4S

)z ,y ,(x s2s2s2

1D

2D3D

4D

iD)z ,y ,(x sisisi

PD(x, y, z)

)z ,y ,(x s1s1s11S

2S

)z ,y ,(x s3s3s33S

)z ,y ,(x s4s4s4

iS

4S

)z ,y ,(x s2s2s2

1D

2D3D

4D

iD)z ,y ,(x sisisi

PD(x, y, z)

© Doble Lemke / University of Stuttgart


2. PD Measurement

Non Conventional PD Measurement (UHF)

Transformer

Drain Valve Sensor

Top Hatch Sensor

GIS

Window Sensor

Spacer Sensor

Cable

Termination

Sensor

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2. PD Measurement

20

A - PD site in the insulationB - Radiated electromagnetic fieldC - Voltage drop at the HV sideD - Electric field via the stray capacitance to groundE - Magnetic field by the current in the ground lead

A

B

C

D

E



2. PD Measurement

21

2.4 PD Analysis (IEC and VHF/UHF)


3. PD Analysis

22


3. PD Analysis

Classification based on PD-Pattern:

Corona Discharge

Surface Discharge

Void Discharge

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Corona Discharge

24

3. PD Analysis3.1 Corona Discharge


Surface Discharge

27

3. PD Analysis3.2 Surface Discharge


Void Discharge

29

3. PD Analysis3.2 Void Discharge


4. Doble Lemke Solutions

32

Acoustic

PD-Location

•LDP-5/A

•LDA-5

•LDA-6

Non-Conventional

UHF

PD-Detection and Analysis

•LDS-6/UHF

•PD-Smart/UHF

•PD-Guard/UHF

Survey

PD-Detection

•LDP-5

4.1 Measurement Systems

IEC 60270

PD-Detection and Analysis

•LDS-6

•PD-Smart

•PD-Guard



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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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35


Any kind of

DUT



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4.2 PD Measurement Sensors

HFCT

UHF Coupler

UHF AntennaIEC 60270

Acoustic

C-Sensor

L-Sensor

Window-Sensor

TEV-Sensor

1 pd training fundamentals of partial discharge

Documents

partial dischargecontents1

dielectric causing pd

pd measurement3

pd analysis4

solid insulation systems

fundamentalspartial

type of breakdown

boundary surfacecracks