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 ......
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