Basic Partial Discharge

Tiara Vibrasindo Pratama
1
Basic Partial
Discharge
TIARA VIBRASINDO PRATAMA
15 – 17 SEPTEMBER 2015
Introduction
 Mauritz Roni Gabe Manurung
 Electrical Engineer
 mauritz@tiaravib.com
 081287461414/081260815213

2
PT. Tiara Vibrasindo Pratama :
-
-
-
Predictive maintanance services
Conditional Failure Monitoring Technology
Training and Certification
PT. MTS Indonesia :
- Asset Management Consultant
Head office :
Jln. Penjernihan II No. 5A, Bendungan Hilir
Jakarta Pusat
We are The Reliability Group established 1995
Emerson's Machinery Health Management business is
the ideal choice for developing and enhancing mechanical
reliability because we specialize in machinery analysis.
Mobius offer computer-based training products (in three
languages), public and in-plant training courses, and distance
learning courses.
CTC are committed to being the world leader in the quality
of vibration analysis product and services that CTC provide
to CTC customers.
EPRI provides an integrated portfolio of engineering services,
business consulting, and information products to clients across the
entire power industry.
Reliability Partner

3
EA Technology has provided leading edge power asset management
solutions for over 40 years. Its customers operate across a spectrum of
industries, notably the electricity, rail and industrial sectors, both in the
UK and through a network of distributors across the world. In particular,
they are market-leaders in the areas of Partial Discharge (PD)
me.asurement and Condition Based Risk Management (CBRM)
methodologies.
Reliability Partner
And many other company has joined
Experiences - Competency

4
Topik Pembahasan
Day 1
 General Maintenance
 Partial Discharge
 PD Rotating Machines
 PD
Day 2
 Stator
 Mekanisme Kegagalan
 Analysis
Day 3
 Switchgear
 Mekanisme Kegagalan
 Analysis
Ingatkah terakhir kali ke
dokter?
Demam
Operasi Bypass
Jantung
Suntik Botox
Penggantian
Ginjal per 10
tahun
Cek Up
tahunan
Pemeriksaan
mendalam di
RS

5
Pemeliharaan tubuh dalam
perspektif engineering
filosofi strategy
Demam
Operasi bypass
jantung
Krisis, mendadak Breakdown
maintenance
Suntik botox
Penggantian
ginjal per 10
tahun
Time-based Preventive
maintenance
Cek up Condition based Predictive
maintenance
Bagaimana pemeliharaan aset ?
Demam Alarm temperatur air
Operasy Bypass Jantung Perbaikan winding
Suntik Botox Injeksi resin
Penggantian ginjal per 10
tahun
Rewinding per 10 tahun
General Cek Up Online monitoring
Pemeriksaan mendalam
rawat inap
Offline test

6
General Maintenance
Ada 4 maintenance yang dilakukan :
 Reactive Maintenance
 Preventive Maintenance
 Predictive Maintenance
 Proactive Maintenance
Reactive Maintenance
Membiarkan mesin beroperasi sampai terjadi kerusakan. Tidak ada
tindakan sebelum terjadi kegagalan.
Disebut juga dengan Run To Failure Maintenance
The philosophy is
“just let it break”

7
Reactive Maintenance
Keuntungan:
 Murah
 Mesin tidak dirawat secara berlebihan
Kerugian:
 Tidak ada persiapan terhadap terjadinya kerusakan
mesin (downtime) karena terjadinya mendadak.
 Kerusakan akan menyebar ke komponen lain dan
bisa terjadi kerusakan fatal (catastrophic) sehingga
biaya perbaikan akan mahal.
 Kerugian produksi besar.
Preventive Maintenance
Dikenal juga sebagai Calendar-based Maintenance, jenis
perawatan ini menggunakan teori yang menyebutkan
bahwa umur mesin terbatas dan kemungkinan terjadinya
kegagalan akan meningkat seiring dengan meningkatnya
umur mesin.
Jadi kegiatan perawatan akan dilaksanakan sebelum
mesin membutuhkannya.
The philosophy is
“fix it before it break”

8
Terdapat masalah dalam memperkirakan
umur dari mesin sebelum mesin itu
mengalami kegagalan.
Keuntungan:
 Perawatan dilakukan pada waktu yang sudah ditentukan dan
dipersiapkan.
 Kegagalan mesin yang tidak terduga dapat dikurangi.
 Oleh karena itu kerusakan fatal dapat dikurangi.
 Terganggunya jalan produksi bisa dikurangi.
 Ada pengaturan yang jelas terhadap penyimpanan komponen
cadangan dan biaya.
Kerugian:
 Masin terlalu sering diperbaiki bahkan pada saat dimana mesin itu
sebenarnya tidak mengalami masalah sama sekali.
 Tindakan perawatan seringkali menambah masalah daripada
menguranginya.
 Masih terjadi unscheduled breakdowns.

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Predictive Maintenance
Predictive maintenance, disebut juga dengan Condition Based
Maintenance adalah suatu proses yang membutuhkan
teknologi dan keahlian orang yang menggabungkan
semua data diagnostik dan performance yang ada,
maintenance histories, data operasi dan desain untuk
membuat keputusan kapan harus dilakukan tindakan
perawatan pada major / critical equipment.
The philosophy is
“if it ain’t broken, don’t fix it”
Keuntungan:
 Kerusakan mesin (downtime) yang tidak terduga dapat
dikurangi.
 Komponen hanya dipesan saat dibutuhkan jadi
penumpukan stok komponen bisa lebih dikurangi.
 Tindakan perawatan bisa lebih direncanakan.
Kerugian:
 Biaya yang tinggi dalam mempersiapkan peralatan
instrumen dan tenaga ahli.
 Tidak ada kepastian apakah umur mesin bisa lebih
panjang.

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•PDM Program
–Alerting
–Diagnostics
–Root Cause Failure
–Performance metrics
–Communications
–Skills
Diagnostic &
Process Data
Periodic
Diagnostic
Data
Operator Log
Data
Design &
Historical Data
Design &
Historical Data
Engineering
Maintenance
Operations
Engineering
Maintenance
Operations
Maintenance
Planning
Scheduling
Batch Testing &
Inspection Data
Maintenance
Histories &
Records Data
Teknologi Predictive Maintenace
PDM Mesin
 Infrared
 Vibration
 Ultrasound
 Shaft Voltage
 Oil Analysis
 MCSA
 Rotor Flux
 DGA
PDM Manusia
 Thermometer
 ?
 Cek THT
 Cek Osteoporosis
 Cek Darah
 ?
 Cek Paru-paru
 ?

11
Masih ingat ?
Signal PD
Detected
Effect PD
Detected
Kendalikan Takdir Aset Anda
PD Monitoring Rewinding tiap 10
tahun
Menunggu dan
berdoa hasil OH
baik
Lapor kegagalan
mesin ke atasan

12
Mengapa PD sebagai parameter
PdM ?
Failure Mechanism dengan gejala PD
membutuhkan waktu yang lama untuk
merusak insulasi sepenuhnya
NAMUN
Beberapa problem bisa menyebabkan
kegagalan hanya dalam 2 menit apabila
tidak dimonitor
Proactive Maintenance
Dikenal juga sebagai Precision Maintenance dan Reliability
Based Maintenance. Metode perawatan ini lebih
menitikberatkan pada indentifikasi akar permasalahan dan
memperbaikinya untuk mengurangi kemungkinan mesin
akan rusak.
The philosophy is
“fix it once and fix it right”

13
Memaksimalkan umur operasi mesin dan meningkatkan
keandalan serta efisiensinya melalui :
 Analisa penyebab kegagalan (Root Cause Failure Analysis)
 Instalasi mesin dilakukan dengan kepresisian yang tinggi.
 Pelatihan personel.
3 hal yang harus ditelusuri:
 Mengapa mesin selalu mengalami kegagalan berulang-ulang ?
 Jenis tindakan apa yang harus dilakukan ?
 Apakah mesin beserta komponen-komponennya telah terpasang
dengan benar ?
Keuntungan:
 Umur operasi mesin bisa lebih diperpanjang
 Keandalan mesin meningkat
 Kegagalan mesin dapat dikurangi
 Biaya perawatan keseluruhan bisa dikurangi
Kerugian:
 Investasi dengan biaya tinggi untuk peralatan instrumen dan
keahlian personel
 Diperlukan keahlian khusus dari para personelnya.
 Dibutuhkan investasi waktu untuk menerapkan metode ini.

14
Why Test for Partial Discharge?
 How to prevent Motors and Generators failure in-service?
Need a predictive maintenance tool
1. 50% due to bearing/vibration problems – Mechanical
• SOLUTION: On-Line Vibration Analysis
2. 40% due to Stator Insulation Problems – Electrical
• SOLUTION: On-Line PD Testing
3. 10% due to rotor problems – Electrical
• SOLUTION: On-Line Flux or CSA Monitoring
Analysis of MV Switchgear Faults
Ea Technology, 2006

15
Rentang deteksi PD terhadap kerusakan
akibat mekanisme kegagalan
• 10 tahun untuk mesin > 18kV
• 5 tahun untuk mesin 13.8 kV
• 2 – 3 tahun untuk mesin 6 kV
• beberapa bulan untuk mesin 4 kV
Partial Discharge
Partial Discharge (PD) is an electrical
discharge that does not completely bridge
the space between two conducting
electrodes. The discharge may be in a gas
filled void in a solid insulating material, in a
gas bubble in a liquid insulator, or around an
electrode in a gas. When partial discharge
occurs in a gas, it is usually known as corona.

16
Partial Discharge Activity
 Gaseous medium
 Voids or gaps
 Electrical stress
 Electron
e¯
e¯
e¯
e¯
Dielectric Strength
Material Dielectric
Strength
Air ~3 kV/mm
Mineral Oil ~10- 15 kV/mm
Polyethylene ~20 kV/mm
EPR (Rubber) ~25 kV/mm
Vacuum ~20-40 kV/mm
Impregnated
Paper
~20-50 kV/mm
XLPE ~20 kV/mm
SF6 (3.5 bar) ~15 kV/mm

17
What Are Partial Discharges?
 Small electrical sparks in air-
filled cavities in or adjacent
to HV electrical insulation
 They occur when the electric
stress exceeds the electrical
breakdown strength of the air
in the void
 Breakdown strength of air
Eair=Vair/dair = 3 kV/mm
 Breakdown strength of
insulation Einsulation ≈ 300
kV/mm
How Does PD Occur?
 Capacitive voltage builds
across an air-filled void
 PD occurs if Vair/dair >
3kV/mm ( i.e., electrical
stress exceeds electrical
breakdown point of gas)
 Monitor PD by detecting
and measuring the resulting
current pulses
PD occurs if Vair / dair > 3 kV/mm

18
PD Pulse Characteristics
 Extremely fast rise-time current pulse = short
pulse width
 Rise-time at discharge origin ~ 1 to 5 ns
1 － 5 ns
t
I
PD in your Equipment
 Rotating Equipment
 Generator (Stator)
 Motor (Stator)
 Static Equipment
 Switchgear (SF6,CT,PT,BusBar,CableBox,Connection,dLL)
 Transformer (Oil,Bushing,Paper)
 Overheadline (Bushing,Cable)

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PD in Rotating Machines
 Internal Discharge
 Internal Voids
 Internal Delamination
 Slot Discharges
 Discharge in the end winding
 Surface Discharges
 Phase to phase Discharges
 Conductive Particles
Internal Discharge
 Internal Voids
 Cause:
Improper manufacturing
 Process:
Formation of voids
PD attacks insulation
Internal
Air
Voids
11,000 hp, 6.6kV Motor Coils

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Internal Discharge
 Cause:
 Lose of mechanical strength
due to overheating
• Overloading
• Defective cooling
 Process:
– Insulation delamination
– Conductor vibration
– PD occurs in the voids
Insulation
Delamination
Ground fault
Slot Discharge
 Cause:
 Loose windings and
wedges
 Magnetic forces
between bars & between
rotor and stator windings
 Process:
 Bars move relative to
core
 Abrasion of semicon
coating layer
 Partial discharges occur
in the slot
 Produce ozone as a result
of O3 + N2  Nitric acid
Turbo Generator Failure due to
Loose Windings in the Slot
Electrical Slot
Discharge
(Ladder effect
clearly visible)
White
Powder
Residue

21
Discharge Endwinding
 Surface Discharge
 Cause:
 Improper manufacturing
 Over high electric stress
 Over high temperature
 Process
 Grading loses ground contact
 Floats to high voltage
 Interface to ground sparks
 Produces ozone
 White band at slot exit
Endwinding discharges
(Grading/semicon coating fault)
Discharge Endwinding
 Phase to Phase Discharge
 Cause:
 Poor Design
 Process
 Phase to phase PD
 Produce ozone as result of
O3+N2  Nitric acid
 Erode and puncture the
insulation

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 Cause:
– Foreign material entering
machine such as:
Oil, Grease, Dust
 Process:
– Reduces surface resistance
– Electrical tracking
– Insulation erodes over time
Electrical tracking across
blocking,
evident when winding
cleaned
Turbo Endwindings
Electrical tracking
Conductive Particles
Insulation Damage
from Electrical Tracking

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 Internal Discharges: occuring in void or cavities within
solid or liquid dielectrics
 Surface Discharges: appearing at the boundary of the
different insulation materials
 Continuous impact of discharges in solid dielectrics
forming discharge channels (treeing) in organic
materials
 Corona discharge occuring in gaseous dielectrics in
the presence of inhomogeneous fields
PD Static Equipment
PD Static Equipment

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PD
occur
Electromagnetic
Radio Light Heat
Acoustic
Audio Ultrasonic
Gases
Ozone
Nitrous
Oxides
Stator
 Stator Core
 Winding
 Endwinding EndWinding
Winding
Stator Core

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Stator Core
 Purpose
 Made of
Winding
 Purpose
 Made of

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Struktur Belitan
 Multiturn coil, diamond
 Roebel Bar/ Half Coil
Winding Manufacturing Process
1. Bundle the insulated strands (Strand Insulation)
2. Apply turn insulation
3. Form bundle into coils
4. Apply ground insulation tapes
5. Impregnate or press cure
6. Seal the winding (Surface Coating)

27
Insulasi Multiturn Coil
Insulasi Roebel Bar

28
Strand insulation
 Purpose :
to insulate the individual strands
which make up a turn bundle. Turns
are made up of smaller strands to
lower the skin effect and stray
current losses from the axial
magnetic fields. Strands have a
larger surface area (skin) and can
carry more current than a solid
conductor.
Turn insulation
 Purpose :
to prevent shorts between turns and to
provide sufficient dielectric strength to
prevent insulation failure under the
influence of high transient voltages
imposed on the stator windings during
starting, lightening strikes or IFD
operation.

29
Groundwall Insulation
 Purpose :
prevent shorts between the copper
conductors and the grounded stator
core. The thickness of the groundwall
insulation is solely dependent upon
the voltage rating of the machine
and the volts/mm stress chosen by
the manufacturer.
Material Dielectric
Strength
Air ~3 kV/mm
Vacuum ~20-40 kV/mm
Impregnated
Paper
~20-50 kV/mm
XLPE ~20 kV/mm
SF6 (3.5 bar) ~15 kV/mm
Impregnate or press cure
 Conventional VPI
 Global VPI

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Conventional VPI
 Winding dimasukkan satu persatu
 Winding dipanaskan terlebih
dahulu
 Resin (Mika) ditransferkan kedalam
tank
 Lalu di press sampai resin masuk
kembali ke tank vacuum (proses
impregnasi)
 Keluarkan Winding dari tank lalu
dipanaskan menggunakan oven
 Kemudian baru dimasukkan
kedalam stator slot lalu diberikan
wedge (penahan winding)
Global VPI
 Winding diisolasi dengan mica paper
atau mica tapes terlebih dahulu
 Lalu dimasukkan kedalam stator slot
kemudian diberikan wedge.
 Endwinding diberikan penahan dan
juga di tali
 Dimasukkan kedalam tank VPI yang
besar
 Dipanaskan
 VPI tank di tutup dam divacuum
 Proses impregnasi dilakukan
 Lalu Dikeluarkan setelah dilakukan
proses pressure

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Surface Coating
Semiconductive (Conductive)
Coating
 sejenis carbon
 Mencegah surface discharge di
stator slot
Stress Grading Coating
 Silicon carbide
 Non linear resistant
 Overlap semi conductive
coating
 Mencerai beraikan electrical
stress di endwinding
Surface Coating

32
Surface Coating
Kira kira apa kesalahan produksi
yang bisa menimbulkan PD ?

33
Kira kira apa kesalahan produksi
yang bisa menimbulkan PD ?
Mekanisme Kegagalan

34
Types of PD in rotating machines
 Internal Discharges
 Internal Voids
 Delamination between conductor and insulation
 Electrical treeing
 Slot Discharges
 Discharges in the end-winding
 Arcing and sparking
 Arcing at broken conductors
 Vibration sparking
Based on IEC/TS 60034-27
Internal Discharges
 Internal Void
 Cause :
 Improper Manufacturing
 Process :
 Formation of voids
 PD attacks insulation
Internal
Air Voids

35
Internal Discharges
 Cause
 Loose of mechanical strength due to
overheating
 Overloading
 Defective cooling
 Process
• Insulation delamination
 Conductor vibration
 Thermal Deterioration
 PD occurs in the voids
Insulation
Delamination
Ground fault
 Delamination between conductors and
insulation
 Cause
 Load cycling
 Process
 Formation of voids
 PD attacks insulation between conductor
Internal Discharges
Internal
Air Voids

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 Electrical Treeing
 Cause
 Ageing process
 Process
 Internal Voids
 Rough Structures of inner conductors
 Internal Discharges
 Insulation Impurities
 Internal Delamination
Internal Discharges
Slot Discharges
 Cause
 Loose windings and wedges
 Magnetic forces between bars
 Magnetic forces between rotor and stator
 Process
 Bars move relative to core
 Abrasion of semicon coating layer
 Partial Discharges occurs in the slot
 Produce ozone as a result of
O3 + N2  Nitric acidElectrical Slot
Discharge
(Ladder effect
clearly visible)
White
Powder
Residue
Turbo Generator Failure due to
Loose Windings in the Slot

37
Discharges in the End-winding
 Cause
 No stress control coating is no applied
 Contamination
 Porosity
 Thermal effect
 Process
 Stress Control coating ineffective
 Surface exceeds the breakdown field of surrounding gas
 Phase to ground Fault
Discharges in the End-winding
 Cause
 Inadequate Spacing
 Process
 Grading loses ground contact
 Erode and puncture the insulation
 Produce ozone as a results of :
O3+N2 Nitric acid
 White powder

38
 Cause
 Contamination
 Process
 Strong local concentration of Partial
Discharge
 Pin hole in insulation
Arcing and sparking
 Cause
 Mechanical Vibration
 Broken conductors
 Process
 Vibration at winding bars
 Arc from semi-conductive to core iron
 Damage ground-wall insulation by erosion process

39
Noise and Disturbance
Based on IEC/TS 60034-27 :
Noise :
“Noise is defined to be non-stator winding signals that clearly are not
pulse”
Disturbances :
 Electrical pulses relatively in short duration
 May have many of characteristics of Stator winding PD (but in fact not)
 Some are synchronized to the AC cycle (some are non-synchronized)
 Sometimes synchronized disturbance pulses can be suppressed based
on their position with respect to the AC phase angle.
Examples of synchronized disturbances :
a) Partial discharges caused by e.g. electrostatic precipitators or bushing
discharges
b) Power tool operation such as from arc welding and commutator
sparking (may also be unsynchronized)
c) Transients caused by power electronics, for example converter fed
motors or excitation systems. This disturbance may also be unsynchronized
to the AC cycle
d) Poor electrical connections (leading to contact sparking) on the bus or
cable connecting the rotating machine to the power system
e) Poor electrical connections elsewhere in the plant that lead to contact
sparking
f) PD in other apparatus connected to the motor or generator terminals,
for example output bus, power cable, switchgear and/or transformers
g) Arcing or sparking sources within the motor or generator, such as stator
core lamination sparking

40
Examples of non-synchronized disturbances :
h) Power tool operation (arc welding and commutator sparking)
i) Transients caused by power electronics, for example converter fed
motors or static excitation systems
j) Slip ring sparking on the machine rotor
k) Overhead crane power rail sparking
Frequency domain separation
 PD bisa muncul di frekuensi rendah ke frekuensi tinggi
 Sehingga dilakukan separasi dengan lower cut-off frequency dan
upper cut-off frequency
 Based on IEC/TS 60034-27 dibagi menjadi beberapa separasi :
 High Frequency range (HF : 3MHz to 30MHz)
 Very High Frequency (VHF : 30MHz to 300MHz)
 Ultra High Frequency (UHF : 300MHz to 3GHz)
 Low Frequency (LF : below 3 MHz)

41
Time domain separation
 Disturbances PD can be separated with
time domain
Time domain separation have two types :
 Pulse shape analysis
 Time of pulse arrival
(Both types can only be used with a high
bandwidth detection system HF,VHF,UHF)
Klasifikasi Sensor Mesin Sensor
sistem
PD aset X X + Delay
Noise dari
sistem
X + Delay X
Noise dari
bus
X + < Delay X + < Delay

42
Combination of Frequency and
Time domain separation
Time and frequency domain separation can be developed through a
pulse shape analysis to produce a so-called “TF” map that plots the
equivalent time length of the pulses versus their equivalent frequency
content.
Gating
In such cases, trigger circuits can be incorporated
that predict when the disturbance will occur
which then will open a gate to prevent the signal
from the PD sensor at the time of the disturbance
from being counted as stator PD.
Trigger circuit will produce gate.
- When signal is from PD the trigger circuit gate
will close
- When signal is from disturbance the trigger
circuit gate will open

43
Pattern recognition separation
 Separation can be manual and automatic
 On Manual Method :
 Experience of the observer needed
Display in PD instrument will show the positive and negative pulses, the
position of pulses on the AC cycle, as well as the magnitude of the pulse. An
experienced observer can often recognize stator PD and or disturbance.
 On Automated Method (computer-aided):
Pattern recognition is rapidly evolving field of investigation. A number of
pattern recognition methods have been applied to separate PD from
disturbances and indeed separate various failure processes from one
another. Some of the methods include:
 Statistical analysis of the distribution of pulses with respect to AC phase
position, e.g. the mean, standard deviation, skew and kurtosis of the phase
angle for positive and negative pulses. Stator winding PD will likely have
different statistical moments than some types of disturbances.
 Artificial intelligence driven pattern recognition analysis to replicate the
thought processes of an expert who manually distinguishes PD from
disturbances.
 Time-frequency transforms, combined with cluster recognition methods and
fuzzy logic to separate and to identify pulses associated with different failure
processes and types of disturbances
Pattern recognition separation

44
PD Sensors
Dalam prinsipnya PD dapat dideteksi
dengan memancarkan atau
dipancarkan electromagnetic pulse
signals. Sehingga dipakai coupling
capacitor untuk mendeteksi signal PD
yang tiba pada sensor PD yang
diinstall. Akan tetapi signal yang
dipancarkan akan terattenuasi. oleh
sebab itu digunakan antenna yang
dipasangkan dekat dengan sumber
PD
PD Sensors
 Separate capacitance :
 Existing surge capacitor;
 Additional coupling capacitor;
 Capasitance of connecting cables
 Coupling device :
 RLC Networks
 Current transformer including isolation transformers and Rogowski coils.
(RFCT)
 PD Sensors near source PD :
 Antennae specifically designed for PD measurements, such as stator slot
couples
 Slot RTD leads already installed in stator winding

45
Phase Resolved Partial Discharge
(PRPD) Pattern
Based on IEC/TS 60034-27 PRPD
dibagi menjadi :
• Principal Appearance patterns
• Typical Appearance patterns
Principal appearance of phase
Resolved PD(PRPD) Patterns
Negative half-cycle/
Positive PD
Positive half-cycle/
Negative PD

46
Principal PPRD Patterns
Ketika pulsa PD, Positive PD lebih
tinggi dibandingkan dengan
Negative PD, sumber dari PD
kemungkinan melibatkan adanya
kerusakan di semiconductive coating
yang mengakibatkan adanya surface
PD di winding.
Ketika pulsa PD, Negative PD lebih
tinggi dibandingkan dengan Positive
PD, sumber dari PD kemungkinan
melibatkan adanya kerusakan di
semiconductive coating yang
mengakibatkan adanya surface PD di
winding.

47
Ketika pulsa PD, Positive PD dan
Negative PD tidak ada yang
mendominasi (nilai magnitude hampir
sama), sumber PD dapat dikatakan
dari surface discharge pada
endwinding atau internal discharge
dikarenakan delaminasi atau void
pada insulation
Note pada PD between phases, harus
muncul bersamaan sebagai satu
pasang. PD terdeteksi pada satu
phasa akan bergeser kekanan grafik
(mendekati zero crossing dari AC
cycle), kemudian phasa yang lain
akan terdeteksi bergeser kekiri grafik
(mendekati peak dari AC cycle)

48
Typical PRPD Patterns
 Internal Voids
 PRPD Patterns symmetry
between positive and negative
PD
 Negative PDs occur between 00
and 900
 Positive PDs occur between
1800 and 2700
Internal
Air Voids
 Delamination between
conductor and insulation
 PRPD Patterns asymmetric,
Negative PD will be higher than
Positive PD
and 900
1800 and 2700

49
 Slot Partial Discharges
Positive PD will be higher than
Negative PD, combined with
triangular shape
and 900
1800 and 2700
 Corona activity at the junction
of the slot coating and stress
control coating
Positive PD will be higher than
Negative PD, combined with
rounded shape
and 900
1800 and 2700

50
 Surface Tracking Discharges
 Seen like vertical cloud of PD
 Some case PD occur in both
polarities
 Gas Type Discharges
 Seen like horizontal cloud of PD,
relatively constant amplitude
 Present in both polarities of the
voltage

51
Switchgear
Apa saja tipe Isolasi yang
kemungkinan ada di dalam
switchgear ???
Dielectric Strength
Material Dielectric
Strength
Air ~3 kV/mm
Vacuum ~20-40 kV/mm
Impregnated
Paper
~20-50 kV/mm
XLPE ~20 kV/mm
SF6 (3.5 bar) ~15 kV/mm

52
Why Test
 Safety
 Loss of Supply
 Asset Management
Analysis of MV Switchgear Faults
Ea Technology, 2006

53
Common Discharging Components
Component % age of
Sources
Cable Box 36 %
Circuit Breaker 25%
Voltage
Transformer
20%
Busbar 10%
CT Chamber 9%
General figures based on large database of results primarily on 11kV switchgear
Types of Switchgear
 3.3kV to 66kV
 Indoor Metalclad extensible switchboards
 Indoor and Outdoor Ring Main Units

54
PD Clasification
 Internal Discharges: occuring in cavities within solid or
liquid dielectrics
 Surface Discharges: appearing at the boundary of the
different insulation materials
 Continuous impact of discharges in solid dielectrics
forming discharge channels (treeing) in organic
materials
 Corona discharge occuring in gaseous dielectrics in
the presence of inhomogeneous fields
PD Classification

55
So Why ??
PD occur
Electromagnetic
Radio Light Heat
Acoustic
Audio Ultrasonic
Gases
Ozone Nitrous Oxides
Partial Discharge
 Surface Discharge
 Internal Discharge

56
Internal Discharge
(TEV Detection)
 High Frequency
transient signals from
discharge sources
 Travel over switchgear
surfaces
 Detected using
capacitively coupled
probes on switchgear
metalwork
Apa TEV itu sebenarnya ??
 Transient : lasting only for a short time; impermanent
Jadi TEV bisa dikatakan tegangan yang muncul dalam waktu
yang singkat menuju ground.

57
Internal Partial Discharge
Internal Partial Discharge

58
Internal Discharges (TEV)
 Internal discharge activity
 Trainsient Earth Voltage (TEV) Detection
 High Frequency (~ 3 to 80 MHz)
 TEV magnitude is function of
 The amplitude of the discharges
 The attenuation of the propagation path
Example Internal Discharge
 11kV Cast Resin CTs
Long term erosion of insulation
leading to flashover and failure

59
 Overhead Cable Termiantion
 Cable termiantion screen termination

60
Surface Discharge
(Ultrasonic Detection)
 In severe cases, sound may be
audible
 Less severe deterioration may be
detected using ultrasonic detecting
instruments
 Sound spectrum includes 40 Khz
 Primarily spot check measurements
although extended monitoring is
possible
Surface Discharge Activity
 Discharge across
surface of
insulation towards
earth or phase to
phase discharge
 Often
characterised by
low amplitude but
very high
discharge rate

61
Detected by Ultrasonics
Surface Discharge on 11kV Cast
Resin Circuit Breaker Spouts

62
Detected by Ultrasonics
Contamination make a Surface PD

63
Moisture Ingress leading to surface
tracking
Oil degradation leading surface
erosion of insulation

64
Corrosion due to PD activity
1. Greening of fuse caps
2. Rusting of securing bolts
3. Tracking along the glass reinforced
Plastic fuse bar
1
2
3

65
TEV Background Interference
Mobile
Phone
Mast
HV OHL
Variable speed
drive
DC Light fitting
Radio Mast
Battery
Charger
Possible Ultrasonic Background
Interference

66
Practical Non- Intrusive Detection
Methods
 Internal discharge activity
 Transient Earth Voltage
 High Frequency (~ 3 to 80 MHz)
• Surface discharge activity
 Ultrasonic Emission ~ 40 kHz
 TEV Detection – when high amplitude surface discharge
PD Instruments

67
UltraTEV Detector
UltraTEV Detector
 Ideal for first pass surveys of surface and internal PD activity

68
UltraTEV Detector
 TRAFFIC LIGHT display indicates PD levels
UltraTEV Detector
 ESSENTIAL personal safety device

69
UltraTEV Plus+
UltraTEV Plus+
 Quickly locates & mesures surface and internal PD activity

70
UltraTEV Plus+
 INSTANTLY reveals the condition of assets
UltraTEV Plus+
 PLUG-IN OPTIONS for added versatility

71
TEV Functions
 Two TEV display options
 Display with rolling bar
graph indication and
traffic light alarm level
indication
 Display with amplitude,
pulses per cycle and
severity values
Ultrasonic Measurements
 Measurement of surface discharge
activity in range
 7dBµV to 68dBµV
• 40kHz sounds heterodyned to
audioble output with high quality
headphones
• External Ultrasonic sensor port
• User adjustable alarm thresholds
 Preset to UltraTEV Detector
levels

72
Ultrasonic Features
 Separately adjustable
Gain and Volume
settings
 Immediate Red/Green
indication based on
user adjustable alarm
threshold
PD Locator
 Measures the amplitude of discharge in dBmV
 Locates source of discharge through precedence detections using
both probes, resolution 2ns, 0.6m
 Procedure
 Measure background noise
 Survey with one probe only
 Source internal if reading on switchgear > 10dB above background
noise
 Locate using 2 probes

73
UltraTEV Locator
UltraTEV Locator
 SURVEYS & LOCATES PD activity in all substation assets – including
cables

74
UltraTEV Locator
 MEASURES & RECORDS PD activity in all substation assets – including
cables
UltraTEV Locator
 PLUG-IN OPTIONS for greater versatility

75
PD Location
Reporting and
Analysis of Results

76
Assessment of Partial Discharge
Activity in Switchboard
 Partial Discharge Locator (PDL) survey
 Ultrasonic survey of any air insulated components
 Monitor for one week with Partial Discharge Monitor (PDM)
 Analyse results against historical information
Interpretation of results
 Investigate previous failures
 Is there a common failure mode
 Check previous results
 Same switchboard
 Similar switchboards
• Compare against specific information
• Compare against general information

77
Analysis Considerations
 Maximum Level of Partial Discharge
 Maximum Short Term Severity
 Long Term Severity
 Working Voltage
 Equipment component
 History of failures, if any
 Circuit importance
Partial Discharge Severity
Calculations

78
Terimakasih ….

Basic Partial Discharge

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