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
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)
Fundamentals of Partial Discharge
4
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
Fundamentals of Partial Discharge
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
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
Fundamentals of Partial Discharge
7
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
Fundamentals of Partial Discharge
8
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
9
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
10
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
Fundamentals of Partial Discharge
11
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
Fundamentals of Partial Discharge
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)
13
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
Fundamentals of Partial Discharge
Fully Digital PD Detector
2010
Finalization the first generation of PD Monitoring System, PD Guard as PDM System established
14
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
Fundamentals of Partial Discharge
15
2. PD Measurement 2.3 IEC 60270 PD Measurements
Blocking Impedance
Coupling Capacitor
Measurement Quadripole
Fundamentals of Partial Discharge
16
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
Fundamentals of Partial Discharge
Other • Capacitive coupling • Inductive coupling
17
2. PD Measurement 2.4 Non Conventional PD Measurement Methods
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
Fundamentals of Partial Discharge
18
2. PD Measurement 2.4 Non Conventional PD Measurement Methods
Non Conventional PD Measurement (UHF) Transformer Drain Valve Sensor Top Hatch Sensor
GIS Window Sensor Spacer Sensor
Cable Termination Sensor
Fundamentals of Partial Discharge
19
2. PD Measurement 2.4 Non Conventional PD Measurement Methods
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
Fundamentals of Partial Discharge
20
2. PD Measurement 2.4 PD Analysis (IEC and VHF/UHF)
Fundamentals of Partial Discharge
21
3. PD Analysis
Fundamentals of Partial Discharge
22
3. PD Analysis Classification based on PD-Pattern: Corona Discharge Surface Discharge Void Discharge
Fundamentals of Partial Discharge
23
3. PD Analysis 3.1 Corona Discharge
Corona Discharge
Fundamentals of Partial Discharge
24
3. PD Analysis 3.2 Surface Discharge
Surface Discharge
Fundamentals of Partial Discharge
27
3. PD Analysis 3.2 Void Discharge
Void Discharge
Fundamentals of Partial Discharge
29
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
Fundamentals of Partial Discharge
Survey PD-Detection •LDP-5
32
4. Doble Lemke Solutions 4.1 Measurement Systems
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
Fundamentals of Partial Discharge
33
4. Doble Lemke Solutions 4.1 Measurement Systems
Fundamentals of Partial Discharge
34
4. Doble Lemke Solutions 4.1 Measurement Systems
Any kind of DUT
Fundamentals of Partial Discharge
35
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
Fundamentals of Partial Discharge
36
