Basic Partial Discharge

Tiara Vibrasindo Pratama

1

Basic PartialDischargeTIARA VIBRASINDO PRATAMA15 – 17 SEPTEMBER 2015

Introduction

Mauritz Roni Gabe Manurung Electrical Engineer

[email protected]

081287461414/081260815213


2

PT. Tiara Vibrasindo Pratama :---

Predictive maintanance servicesConditional Failure Monitoring TechnologyTraining and Certification

PT. MTS Indonesia :- Asset Management Consultant

Head office :Jln. Penjernihan II No. 5A, Bendungan HilirJakarta Pusat

We are The Reliability Group established 1995

Emerson's Machinery Health Management business isthe ideal choice for developing and enhancing mechanicalreliability because we specialize in machinery analysis.

Mobius offer computer-based training products (in threelanguages), public and in-plant training courses, and distancelearning courses.

CTC are committed to being the world leader in the qualityof vibration analysis product and services that CTC provideto CTC customers.

EPRI provides an integrated portfolio of engineering services,business consulting, and information products to clients across theentire power industry.

Reliability Partner


3

EA Technology has provided leading edge power asset managementsolutions for over 40 years. Its customers operate across a spectrum ofindustries, notably the electricity, rail and industrial sectors, both in theUK 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 PembahasanDay 1 General Maintenance Partial Discharge

PD Rotating Machines PD

Day 2 Stator

Mekanisme Kegagalan Analysis

Day 3 Switchgear

Mekanisme Kegagalan Analysis

Ingatkah terakhir kali kedokter?

DemamOperasi Bypass

Jantung

Suntik BotoxPenggantianGinjal per 10

tahun

Cek Uptahunan

Pemeriksaanmendalam di

RS


5

Pemeliharaan tubuh dalamperspektif engineering

filosofi strategy

DemamOperasi bypass

jantung

Krisis, mendadak Breakdownmaintenance

Suntik botoxPenggantianginjal per 10

tahun

Time-based Preventivemaintenance

Cek up Condition based Predictivemaintenance

Bagaimana pemeliharaan aset ?

Demam Alarm temperatur air

Operasy Bypass Jantung Perbaikan winding

Suntik Botox Injeksi resin

Penggantian ginjal per 10tahun

Rewinding per 10 tahun

General Cek Up Online monitoring

Pemeriksaan mendalamrawat 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 adatindakan 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 berlebihanKerugian: Tidak ada persiapan terhadap terjadinya kerusakan

mesin (downtime) karena terjadinya mendadak. Kerusakan akan menyebar ke komponen lain dan

bisa terjadi kerusakan fatal (catastrophic) sehinggabiaya perbaikan akan mahal.

Kerugian produksi besar.


Dikenal juga sebagai Calendar-based Maintenance, jenisperawatan ini menggunakan teori yang menyebutkanbahwa umur mesin terbatas dan kemungkinan terjadinyakegagalan akan meningkat seiring dengan meningkatnyaumur mesin.

Jadi kegiatan perawatan akan dilaksanakan sebelummesin membutuhkannya.

The philosophy is

“fix it before it break”


8


Terdapat masalah dalam memperkirakanumur 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.


9

Predictive Maintenance

Predictive maintenance, disebut juga dengan Condition BasedMaintenance adalah suatu proses yang membutuhkanteknologi dan keahlian orang yang menggabungkansemua data diagnostik dan performance yang ada,maintenance histories, data operasi dan desain untukmembuat keputusan kapan harus dilakukan tindakanperawatan 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.


10

•PDM Program–Alerting

–Diagnostics

–Root Cause Failure

–Performance metrics

–Communications

–Skills

Diagnostic &Process Data

PeriodicDiagnosticData

Operator LogData

Design &Historical DataDesign &Historical Data

EngineeringMaintenanceOperations

EngineeringMaintenanceOperations

MaintenancePlanningScheduling

Batch Testing &Inspection Data

MaintenanceHistories &Records Data


Teknologi Predictive Maintenace

PDM Mesin Infrared Vibration Ultrasound Shaft Voltage Oil Analysis Partial Discharge MCSA Rotor Flux DGA

PDM Manusia Thermometer ? Cek THT Cek Osteoporosis Cek Darah Partial Discharge ? Cek Paru-paru ?


11

Masih ingat ?Signal PDDetected

Effect PDDetected

Kendalikan Takdir Aset Anda

PD Monitoring Rewinding tiap 10tahun

Menunggu danberdoa hasil OH

baik

Lapor kegagalanmesin ke atasan


12

Mengapa PD sebagai parameterPdM ?

Failure Mechanism dengan gejala PDmembutuhkan waktu yang lama untuk

merusak insulasi sepenuhnya

NAMUN

Beberapa problem bisa menyebabkankegagalan hanya dalam 2 menit apabila

tidak dimonitor

Proactive Maintenance

Dikenal juga sebagai Precision Maintenance dan ReliabilityBased Maintenance. Metode perawatan ini lebihmenitikberatkan pada indentifikasi akar permasalahan danmemperbaikinya untuk mengurangi kemungkinan mesinakan rusak.

The philosophy is

“fix it once and fix it right”


13


Memaksimalkan umur operasi mesin dan meningkatkankeandalan 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 kerusakanakibat 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 DischargePartial Discharge (PD) is an electricaldischarge that does not completely bridgethe space between two conductingelectrodes. The discharge may be in a gasfilled void in a solid insulating material, in agas bubble in a liquid insulator, or around anelectrode in a gas. When partial dischargeoccurs 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 StrengthMaterial Dielectric

StrengthAir ~3 kV/mm

Mineral Oil ~10- 15 kV/mm

Polyethylene ~20 kV/mm

EPR (Rubber) ~25 kV/mm

Vacuum ~20-40 kV/mm

ImpregnatedPaper

~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 adjacentto HV electrical insulation

They occur when the electricstress exceeds the electricalbreakdown strength of the airin the void

Breakdown strength of airEair=Vair/dair = 3 kV/mm

Breakdown strength ofinsulation Einsulation ≈ 300kV/mm

How Does PD Occur? Capacitive voltage builds

across an air-filled void

PD occurs if Vair/dair >3kV/mm ( i.e., electricalstress exceeds electricalbreakdown point of gas)

Monitor PD by detectingand measuring the resultingcurrent 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)


19

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 VoidsCause:

Improper manufacturing

Process:Formation of voidsPD attacks insulation

InternalAirVoids

11,000 hp, 6.6kV Motor Coils


20

Internal Discharge

Internal Delamination Cause:

Lose of mechanical strength

due to overheating

• Overloading• Defective cooling

Process:– Insulation delamination– Conductor vibration– PD occurs in the voids

InsulationDelamination

Ground fault

Slot Discharge Cause:

Loose windings andwedges

Magnetic forcesbetween bars & betweenrotor 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 toLoose Windings in the Slot

Electrical SlotDischarge(Ladder effectclearly visible)

WhitePowderResidue


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 DischargeCause:

Poor DesignProcess

Phase to phase PD Produce ozone as result of

O3+N2 Nitric acid Erode and puncture the

insulation


22

Cause:– Foreign material entering

machine such as:Oil, Grease, Dust

Process:– Reduces surface resistance– Electrical tracking– Insulation erodes over time

Electrical tracking acrossblocking,evident when windingcleaned

Turbo EndwindingsElectrical tracking


Insulation Damagefrom Electrical Tracking



23

Internal Discharges: occuring in void or cavities withinsolid or liquid dielectrics

Surface Discharges: appearing at the boundary of thedifferent insulation materialsContinuous impact of discharges in solid dielectrics

forming discharge channels (treeing) in organicmaterials

Corona discharge occuring in gaseous dielectrics inthe presence of inhomogeneous fields

PD Static Equipment

PD Static Equipment


24

PDoccur

Electromagnetic

Radio Light Heat

Acoustic

Audio Ultrasonic

Gases

Ozone NitrousOxides

Stator

Stator Core Winding

Endwinding EndWinding

Winding

Stator Core


25

Stator Core

Purpose

Made of

Winding

Purpose

Made of


26

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 tapes5. 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 strandswhich make up a turn bundle. Turnsare made up of smaller strands tolower the skin effect and straycurrent losses from the axialmagnetic fields. Strands have alarger surface area (skin) and cancarry more current than a solidconductor.

Turn insulation Purpose :

to prevent shorts between turns and toprovide sufficient dielectric strength toprevent insulation failure under theinfluence of high transient voltagesimposed on the stator windings duringstarting, lightening strikes or IFDoperation.


29

Groundwall Insulation Purpose :

prevent shorts between the copperconductors and the grounded statorcore. The thickness of the groundwallinsulation is solely dependent uponthe voltage rating of the machineand the volts/mm stress chosen bythe manufacturer.

Material DielectricStrength

Air ~3 kV/mm




Vacuum ~20-40 kV/mm

ImpregnatedPaper

~20-50 kV/mm

XLPE ~20 kV/mm

SF6 (3.5 bar) ~15 kV/mm

Impregnate or press cure

Conventional VPI

Global VPI


30

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 (prosesimpregnasi)

Keluarkan Winding dari tank laludipanaskan menggunakan oven

Kemudian baru dimasukkankedalam stator slot lalu diberikanwedge (penahan winding)

Global VPI

Winding diisolasi dengan mica paperatau mica tapes terlebih dahulu

Lalu dimasukkan kedalam stator slotkemudian diberikan wedge.

Endwinding diberikan penahan danjuga di tali

Dimasukkan kedalam tank VPI yangbesar

Dipanaskan VPI tank di tutup dam divacuum Proses impregnasi dilakukan Lalu Dikeluarkan setelah dilakukan

proses pressure


31

Surface Coating

Semiconductive (Conductive)Coating

sejenis carbon

Mencegah surface discharge distator slot

Stress Grading Coating Silicon carbide

Non linear resistant

Overlap semi conductivecoating

Mencerai beraikan electricalstress di endwinding

Surface Coating


32

Surface Coating

Kira kira apa kesalahan produksiyang bisa menimbulkan PD ?


33

Kira kira apa kesalahan produksiyang bisa menimbulkan PD ?

Mekanisme Kegagalan


34

Types of PD in rotating machines Internal Discharges

Internal Voids Internal Delamination Delamination between conductor and insulation Electrical treeing

Slot Discharges Discharges in the end-winding

Surface Discharges Phase to phase Discharges

Conductive Particles 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

InternalAir Voids


35

Internal Discharges Internal Delamination

Cause Loose of mechanical strength due to

overheating Overloading

Defective cooling

Process• Insulation delamination

Conductor vibration

Thermal Deterioration

PD occurs in the voids

InsulationDelamination

Ground fault

Delamination between conductors andinsulation Cause

Load cycling


Process Formation of voids

PD attacks insulation between conductor

Internal Discharges

InternalAir Voids



36

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 SlotDischarge(Ladder effectclearly visible)

WhitePowderResidue

Turbo Generator Failure due toLoose Windings in the Slot


37

Discharges in the End-winding

Surface Discharges 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

Phase to phase Discharges Cause

Inadequate Spacing


Process Grading loses ground contact

Erode and puncture the insulation

Produce ozone as a results of :

O3+N2Nitric acid

White powder


38


Conductive Particles 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 notpulse”

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 bushingdischargesb) Power tool operation such as from arc welding and commutatorsparking (may also be unsynchronized)c) Transients caused by power electronics, for example converter fedmotors or excitation systems. This disturbance may also be unsynchronizedto the AC cycled) Poor electrical connections (leading to contact sparking) on the bus orcable connecting the rotating machine to the power systeme) Poor electrical connections elsewhere in the plant that lead to contactsparkingf) PD in other apparatus connected to the motor or generator terminals,for example output bus, power cable, switchgear and/or transformersg) Arcing or sparking sources within the motor or generator, such as statorcore 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 fedmotors or static excitation systems

j) Slip ring sparking on the machine rotork) 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 withtime domainTime domain separation have two types :

Pulse shape analysis

Time of pulse arrival

(Both types can only be used with a highbandwidth detection system HF,VHF,UHF)

Klasifikasi Sensor Mesin Sensorsistem

PD aset X X + Delay

Noise darisistem

X + Delay X

Noise daribus

X + < Delay X + < Delay


42

Combination of Frequency andTime domain separation

Time and frequency domain separation can be developed through apulse shape analysis to produce a so-called “TF” map that plots theequivalent time length of the pulses versus their equivalent frequencycontent.

Gating

In such cases, trigger circuits can be incorporatedthat predict when the disturbance will occurwhich then will open a gate to prevent the signalfrom the PD sensor at the time of the disturbancefrom being counted as stator PD.Trigger circuit will produce gate.

- When signal is from PD the trigger circuit gatewill close

- When signal is from disturbance the triggercircuit 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, theposition of pulses on the AC cycle, as well as the magnitude of the pulse. Anexperienced observer can often recognize stator PD and or disturbance.

On Automated Method (computer-aided):Pattern recognition is rapidly evolving field of investigation. A number ofpattern recognition methods have been applied to separate PD fromdisturbances and indeed separate various failure processes from oneanother. Some of the methods include:

Statistical analysis of the distribution of pulses with respect to AC phaseposition, e.g. the mean, standard deviation, skew and kurtosis of the phaseangle for positive and negative pulses. Stator winding PD will likely havedifferent statistical moments than some types of disturbances.

Artificial intelligence driven pattern recognition analysis to replicate thethought processes of an expert who manually distinguishes PD fromdisturbances.

Time-frequency transforms, combined with cluster recognition methods andfuzzy logic to separate and to identify pulses associated with different failureprocesses and types of disturbances

Pattern recognition separation


44

PD Sensors

Dalam prinsipnya PD dapat dideteksidengan memancarkan ataudipancarkan electromagnetic pulsesignals. Sehingga dipakai couplingcapacitor untuk mendeteksi signal PDyang tiba pada sensor PD yangdiinstall. Akan tetapi signal yangdipancarkan akan terattenuasi. olehsebab itu digunakan antenna yangdipasangkan dekat dengan sumberPD

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 PRPDdibagi menjadi :• Principal Appearance patterns• Typical Appearance patterns

Principal appearance of phaseResolved PD(PRPD) Patterns

Negative half-cycle/Positive PD

Positive half-cycle/Negative PD


46

Principal PPRD Patterns

Ketika pulsa PD, Positive PD lebihtinggi dibandingkan denganNegative PD, sumber dari PDkemungkinan melibatkan adanyakerusakan di semiconductive coatingyang mengakibatkan adanya surfacePD di winding.


Ketika pulsa PD, Negative PD lebihtinggi dibandingkan dengan PositivePD, sumber dari PD kemungkinanmelibatkan adanya kerusakan disemiconductive coating yangmengakibatkan adanya surface PD diwinding.


47


Ketika pulsa PD, Positive PD danNegative PD tidak ada yangmendominasi (nilai magnitude hampirsama), sumber PD dapat dikatakandari surface discharge padaendwinding atau internal dischargedikarenakan delaminasi atau voidpada insulation


Note pada PD between phases, harusmuncul bersamaan sebagai satupasang. PD terdeteksi pada satuphasa akan bergeser kekanan grafik(mendekati zero crossing dari ACcycle), kemudian phasa yang lainakan terdeteksi bergeser kekiri grafik(mendekati peak dari AC cycle)


48

Typical PRPD Patterns

Internal Voids PRPD Patterns symmetry

between positive and negativePD

Negative PDs occur between 00

and 900

Positive PDs occur between1800 and 2700

InternalAir Voids


Delamination betweenconductor and insulation PRPD Patterns asymmetric,

Negative PD will be higher thanPositive PD


and 900



49


Slot Partial Discharges PRPD Patterns asymmetric,

Positive PD will be higher thanNegative PD, combined withtriangular shape


and 900



Corona activity at the junctionof the slot coating and stresscontrol coating PRPD Patterns asymmetric,

Positive PD will be higher thanNegative PD, combined withrounded shape


and 900



50


Surface Tracking Discharges Seen like vertical cloud of PD

Some case PD occur in bothpolarities


Gas Type Discharges Seen like horizontal cloud of PD,

relatively constant amplitude

Present in both polarities of thevoltage


51

Switchgear

Apa saja tipe Isolasi yangkemungkinan ada di dalamswitchgear ???

Dielectric Strength

Material DielectricStrength

Air ~3 kV/mm




Vacuum ~20-40 kV/mm

ImpregnatedPaper

~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 ofSources

Cable Box 36 %Circuit Breaker 25%

VoltageTransformer

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 orliquid dielectrics

Surface Discharges: appearing at the boundary of thedifferent insulation materialsContinuous impact of discharges in solid dielectrics

forming discharge channels (treeing) in organicmaterials

Corona discharge occuring in gaseous dielectrics inthe 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 Frequencytransient signals fromdischarge sources

Travel over switchgearsurfaces

Detected usingcapacitively coupledprobes on switchgearmetalwork

Apa TEV itu sebenarnya ?? Transient : lasting only for a short time; impermanentJadi TEV bisa dikatakan tegangan yang muncul dalam waktuyang 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 insulationleading to flashover and failure


59

Example Internal Discharge

Overhead Cable Termiantion

Example Internal Discharge Cable termiantion screen termination


60

Surface Discharge(Ultrasonic Detection) In severe cases, sound may be

audible

Less severe deterioration may bedetected using ultrasonic detectinginstruments

Sound spectrum includes 40 Khz

Primarily spot check measurementsalthough extended monitoring ispossible

Surface Discharge Activity Discharge across

surface ofinsulation towardsearth or phase tophase discharge

Oftencharacterised bylow amplitude butvery highdischarge rate


61

Surface Discharge ActivityDetected by Ultrasonics

Surface Discharge on 11kV CastResin Circuit Breaker Spouts


62

Surface Discharge ActivityDetected by Ultrasonics

Contamination make a Surface PD


63

Moisture Ingress leading to surfacetracking

Oil degradation leading surfaceerosion of insulation


64

Corrosion due to PD activity

1. Greening of fuse caps2. Rusting of securing bolts3. Tracking along the glass reinforcedPlastic fuse bar

1

23


65

TEV Background Interference

MobilePhoneMast

HV OHL

Variable speeddrive

DC Light fitting Radio Mast

BatteryCharger

Possible Ultrasonic BackgroundInterference


66

Practical Non- Intrusive DetectionMethods

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 bargraph indication andtraffic light alarm levelindication

Display with amplitude,pulses per cycle andseverity values

Ultrasonic Measurements Measurement of surface discharge

activity in range 7dBµV to 68dBµV

• 40kHz sounds heterodyned toaudioble output with high qualityheadphones

• External Ultrasonic sensor port

• User adjustable alarm thresholds Preset to UltraTEV Detector

levels


72

Ultrasonic Features

Separately adjustableGain and Volumesettings

Immediate Red/Greenindication based onuser adjustable alarmthreshold

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 backgroundnoise

Locate using 2 probes


73

UltraTEV Locator

UltraTEV Locator

SURVEYS & LOCATES PD activity in all substation assets – includingcables


74

UltraTEV Locator

MEASURES & RECORDS PD activity in all substation assets – includingcables

UltraTEV Locator

PLUG-IN OPTIONS for greater versatility


75

PD Location

Reporting andAnalysis of Results


76

Assessment of Partial DischargeActivity 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 SeverityCalculations


78

Terimakasih ….