5 Pd Training Pd Diagnostics Switchgear

Partial Discharge Diagnostics on Switchgears Dipl.-Ing. Falk-Rüdiger Werner Doble Lemke, Germany [email protected]

Contents

1. Introduction 2. PD Detection Principles on Switchgears 3. PD Measurements on Switchgears

4. Summary of PD Solutions for Switchgears Partial Discharge Diagnostics on Power Transformers

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1. Introduction 1.1 Why online PD diagnostics on switchgears?

Why online PD diagnostics on switchgears? • Risk assessment • Health assessment under online conditions • No downtimes

• Detection of problems at an early stage • Planning of maintenance work • To ensure safe operation and to prolong the asset‘s liftetime Partial Discharge Diagnostics on Power Transformers

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1. Introduction 1.1 Why online PD diagnostics on switchgears?

Why online PD diagnostics on switchgears?

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1. Introduction 1.2 PD Fault Scenarios

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

Sharp Edge

 Surface discharges  Generally faced problem  Countermeasures

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. Introduction 1.2 PD Fault Scenarios

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. Introduction 1.2 PD Fault Scenarios

Fault Distribution (CIGRE JWG 33/23.12) • 41% Switching Compartements: Circuit breakers • 17% VTs, Surge Arrestors , Bushings • 42% others…

Cause of Fault • 20% Free particles and alien objects • 18% Shielding and electrostatitic contacts

• 11% Poor contacts • 7% Moisture • 5% Protrusions, particles on HV

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1. Introduction 1.2 PD Fault Scenarios

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2. PD Detection Principles on Switchgears 2.1 PD Detection Principles

PD Detection Principles

Acoustic • Ultrasonic transducers

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

IEC 60270 • Standard measurement circuit

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2. PD Detection Principles on Switchgears 2.2 PD measurement according to IEC 60270

DUT

Impedance in Series to Ck

• Connection to conductor required (coupling capacitor, bushing) • Mainly used for air insulated switchgears

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2. PD Detection Principles on Switchgears 2.2 PD measurement according to IEC 60270

Apparent Charge Information

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2. PD Detection Principles on Switchgears 2.3 Acoustic PD Detection

Acoustic Partial Discharge Detection  Acoustic signal as a result of the pressure build-up caused by the generated spark in the insulation  Frequency spectrum 10 Hz up to 300 kHz  Different wave types (longitudinal and transversal waves) with different propagation velocities

Measurement Technique  Microphones and ultrasonic directional microphones  Sound sensors, accelerometers and piezo-electric converters

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2. PD Detection Principles on Switchgears 2.4 UHF PD Detection

Spacer

external sensor ultra wide band inductive coupler

standard coupling capacitance

external sensor acoustic coupler

external sensor window sensor

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internal sensor capacitive (sensor

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2. PD Detection Principles on Switchgears 2.4 UHF PD Detection

UHF – Partial Discharge Detection 

Transient electromagnetic waves (TEM, TE and TM modes) generated by partial discharges



Frequency range 300 MHz to 3 GHz



Measuring technique Narrow band-bandwidth appr. 5 MHz Wide band-frequency range 300 MHz to 1,5 GHz



In 420 kV plants – upper critical frequency 1 GHz



In 123 kV plants – upper critical frequency 1,5 GHz

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3. PD Measurement on Switchgears 3.1 GIS Commissioning Test

(1) Resonance test set connected via bushings, (2) Sensors, (3) PD Detector, (4) Sensitivity Check

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3. PD Measurement on Switchgears 3.1 GIS Commissioning Test, Noise Properties

Comparison of IEC60270 and UHF decoupling in terms of noise supression

UHF decouplong at 770 MHz, background noise: 9mV (baseline) No noise

IEC 60270 compliant measurement, noise by testset (1) and external noises (2)

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3. PD Measurement on Switchgears 3.1 GIS Commissioning Test, Noise Properties

No apparent charge information - Detection and classification only

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3. PD Measurement on Switchgears 3.2 Acoustic PD Measurement

DFA100 acoustic PD measurement device with piezo electric sensor

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3. PD Measurement on Switchgears 3.2 Acoustic PD Measurement

Acoustic PD measurements on GIS: 1. Selection of one measurement point per chamber 2. At long chambers, one measurement point every 2-3 meters

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3. PD Measurement on Switchgears 3.2 Acoustic PD Measurement

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4. Summary of PD Solutions for Switchgears

PD Solutions

Acoustic DFA100 • PD location and detection • PD Classification

UHF/VHF/RF LDS-6/UHF, PD-Smart/UHF • Sensitive PD detection • PD Classification

IEC 60270 LDS-6, PD-Smart • Factory tests • Commissioning tests

PD-Guard/UHF • Monitoring

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Thank you for your attention

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