Partial Discharge Training

• Apa itu Partial Discharge ?• Apa penyebab Partial Discharge ?• Bagaimana Mengukur Partial Discharge?

Question ....

Apa saja tipe Isolasi yang kemungkinan ada didalam switchgear ???

Dielectric StrengthMaterial 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

Partial Discharge Activity

• Gaseous medium• Voids or gaps

• Electrical stress• Elektron

e¯

e¯

e¯

e¯

Teori ....

• Bagaimana sebenarnya Partial Discharge ituterjadi ???!!

Partial discharge terjadi ketika electrical stressmelebihi 3kV/mm

Discharge in Gas ...• Untuk medan listrik homogen antara dua

elektroda• Jika E cukup tinggi : akan dimulai dengan ionisasi Elektron akan lebih cepat dan bertabrakan dengan

molekul Jika kecepatanya cukup cepat : ionisasi akan berlanjut

karena energi kinetik dari elektron Terjadi reaksi berantai: gas menjadi plasma, maka

aka terjadi thermo-ionisasi Lalu akan timbul percikan yang mengakibatkan

breakdown

Electrical field

• Untuk medan listrik non-homogen: E tinggi diujung, rendah pada plate

• PD dimulai jika E lebih tinggi daripada E critical• Perilaku PD tergantung pada E:

– Voltage level dan ukuran

Partial Discharge adalah .....

peristiwa pelepasan/ loncatan bunga api listrikyang terjadi pada suatu bagian isolasi (padarongga dalam atau permukaan) sebagai akibatadanya beda potensial yang tinggi dalam isolasitersebut.

Why Test

• Safety• Loss of Supply• Asset Management

Analysis of MV Switchgear Faults

Ea Technology, 2006

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

PD Clasification

• Internal Discharges: occuring in cavities within solid or liquiddielectrics

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

forming discharge channels (treeing) in organic materialsCorona discharge occuring in gaseous dielectrics in the

presence of inhomogeneous fields

PD Classification

So Why ??

PD occur

Electromagnetic

Radio Light Heat

Acoustic

Audio Ultrasonic

Gases

Ozone Nitrous Oxides

Partial Discharge

• Surface Discharge• Internal Discharge

Internal Discharge(TEV Detection)

• High Frequency transientsignals from dischargesources

• Travel over switchgearsurfaces

• Detected using capacitivelycoupled probes onswitchgear metalwork

Apa TEV itu sebenarnya ??

• Transient : lasting only for a short time; impermanentJadi TEV bisa dikatakan tegangan yang muncul dalamwaktu yang singkat menuju ground.

Internal Partial Discharge

Internal Partial Discharge

Transient Earth Voltage (TEVs)

TEV (mV) dB

1 0

1.12 1

1.78 5

3.16 10

10 20

31.6 30

100 40

316 50

1000 60

1410 63

http://www.naval.com/help/db-x.htm

Internal Discharges (TEV)

• Internal discharge activityTrainsient Earth Voltage (TEV) DetectionHigh 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

Example Internal Discharge

• Overhead Cable Termiantion

Example Internal Discharge

• Cable termiantion screen termination

Surface Discharge(Ultrasonic Detection)

• In severe cases, sound may beaudible

• Less severe deterioration may bedetected using ultrasonicdetecting instruments

• Sound spectrum includes 40 Khz

• Primarily spot checkmeasurements although extendedmonitoring is possible

Surface Discharge Activity

• Discharge acrosssurface of insulationtowards earth orphase to phasedischarge

• Often characterisedby low amplitude butvery high dischargerate

Surface Discharge Activity Detected byUltrasonics

Surface Discharge on 11kV Cast ResinCircuit Breaker Spouts

Surface Discharge Activity Detected byUltrasonics

Contamination make a Surface PD

Moisture Ingress leading to surfacetracking

Oil degradation leading surfaceerosion of insulation

Corrosion due to PD activity

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

1

23

TEV Background Interference

MobilePhoneMast

HV OHL

Variable speeddrive

DC Light fitting Radio Mast

BatteryCharger

Possible Ultrasonic BackgroundInterference

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

UltraTEV Detector

UltraTEV Detector

• Ideal for first pass surveys of surface andinternal PD activity

UltraTEV Detector

• TRAFFIC LIGHT display indicates PD levels

UltraTEV Detector

• ESSENTIAL personal safety device

UltraTEV Plus+

UltraTEV Plus+

• Quickly locates & mesures surface andinternal PD activity

UltraTEV Plus+

• INSTANTLY reveals the condition of assets

UltraTEV Plus+

• PLUG-IN OPTIONS for added versatility

TEV Functions

• Two TEV display options

• Display with rolling bar graphindication and traffic lightalarm level indication

• Display with amplitude,pulses per cycle and severityvalues

Ultrasonic Measurements

• Measurement of surface dischargeactivity in range 7dBµV to 68dBµV

• 40kHz sounds heterodyned to audiobleoutput with high quality headphones

• External Ultrasonic sensor port

• User adjustable alarm thresholds Preset to UltraTEV Detector levels

Ultrasonic Features

• Separately adjustable Gainand Volume settings

• Immediate Red/Greenindication based on useradjustable 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

• ProcedureMeasure background noiseSurvey with one probe onlySource internal if reading on switchgear > 10dB above

background noiseLocate using 2 probes

UltraTEV Locator

UltraTEV Locator

• SURVEYS & LOCATES PD activity in allsubstation assets – including cables

UltraTEV Locator

• MEASURES & RECORDS PD activity in allsubstation assets – including cables

UltraTEV Locator

• PLUG-IN OPTIONS for greater versatility

PD Location

Reporting and Analysis of Results

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

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

Terimakasih ......