Uploaded byNitinPandya14
PDF, PPTX196 views

IEEE-Alberta_Partial-Discharge.pdf

EA Technology is a 100% employee-owned company that was originally established in the late 1960s as an R&D center for the UK electricity industry. It provides asset condition assessment, instrumentation, and asset management software and consulting services related to partial discharge detection and diagnosis. Partial discharge refers to a localized breakdown of insulation within an electrical apparatus that does not completely bridge the insulation gap. It can occur due to defects, voids, contamination, or other issues and causes damage over time if left unaddressed. Various online and offline detection techniques exist to identify and locate partial discharge.

Embed presentation

Download as PDF, PPTX
Introduction to Partial Discharge (Causes, Effects, and Detection) Presented by: Tim Erwin National Sales Manager O 862 261 2759 C 862 222 3666 Email: Tim.erwin@eatechnologyusa.com
EA Technology History & Values • Originally established as R&D center for the UK Electricity Industry (essentially EA Technology was the EPRI of the UK) in the late 1960’s. Privatized in the late 1990s. • Provides research, strategic engineering consultancy, HV asset condition assessment services, specialized instrumentation, and Asset Management Software and Consulting. • Instrumental in the development of PAS-55 and ISO-55000 • 100% employee owned and have provided products and service in 92 countries around the world EA Technology Capenhurst UK EA Technology LLC Denville, NJ - USA
Partial Discharge – What is it and why do we care?
6 Is Partial Discharge Real?
PD failure process • Multiple causes • Starts small • ALWAYS gets worse • Leads to FLASHOVER What is Partial Discharge? PD is the inability of a portion of the insulation to withstand the electric field applied to it
Partial Discharge (PD) The key to OUTAGE PREVENTION •3.3kV to 769kV •Indoor Metal clad switchgear cubicles •Indoor and Outdoor Insulators •Transformer Cable Boxes •MV & HV Cables, Terminations & Underground Vaults •Transformers •SF6 GIS / Oil Filled / Air Insulated Where can it occur?
Partial Discharge - A flashover of part of the insulation system due to a localized electric field greater than the dielectric withstand capability of that part where the overall insulation system remains capable of withstanding the applied electrical field. Void Ground Conductor V withstand of C2 < applied field V withstand of C1&C3 > applied field 9 What is Partial Discharge (PD)? One effect of this flashover is a high frequency current pulse that travels through the capacitance of the insulation (C1 & C3) HF Current Pulse C1 C2 C3
Equipotential Lines Voltage 0 V X kV 6X voltage drop Section through a homogenous insulator showing uniform electrical stress (equipotential) lines. A line indicates where the voltage potential is constant The same insulator with a void. The lower dielectric of the void causes a concentration of the electrical field through the void high enough to cause breakdown at working voltages
11 Products of Partial Discharge Partial discharge breakdown of insulation produces: Light, Heat, Smell, Sound, Electromagnetic Waves, and an HF Electric Current Electric TEV I
12 Products of Partial Discharge Partial discharge breakdown of insulation produces: Light, Heat, Smell, Sound, Electromagnetic Waves, and an HF Electric Current + Water Nitric Acid Electric TEV How does PD damage insulation? I
UK utility undertook a two year evaluation of RFCT based on-line testing that performed a PD condition based assessment of 191 33KV cables on their network over a two year period. 84% rated GREEN (no problems) >2% of those failed within 2 years 7% rated Amber (no problems) <21% of those failed within 2 years 7% rated RED (no problems) <40% of those failed within 2 years CABLE TESTING Field Example
Types of PD •Internal discharges occurring in defects, voids or cavities within solid insulation •Surface discharges occurring across the insulation surface •Contact discharge occurs on floating metal in high field conditions •Corona discharge occurring in gaseous dielectrics in the presence of inhomogeneous fields
• Internal Discharge occurs in all types of insulation as a result of defects, voids or cavities within solid insulation, also including oil and gas • Practical Non-Invasive method to detect Internal Partial Discharge Activity is to use Transient Earth Voltage (TEV) detection instruments. Partial Discharge (PD) Internal Partial Discharge
• Surface discharges occurring across the insulation surface Causes treeing and tracking • Practical Non-Invasive method to detect Surface Partial Discharge Activity is to use Ultrasonic Emission detection instruments. Partial Discharge (PD) Surface PD
Causes of PD • Surface contamination (lack of cleaning) • Workmanship (poor installation) • Material defects (manufacturing defects) • Improper application (wrong parts for the job) • Salt spray or Salt fog • Mechanical damage (during install or in service) • Age (electrical stress wears out insulation)
Standards associated with PD
IEEE 400 Series IEEE 400 Guide to field testing shielded power cable • Cables only IEEE 400.1 Guide to testing shielded power cable with DC • Not for Aged XLP cable • Fine for PILC • i.e. IEEE 400.2 Guide to field testing shielded power cable with VLF • Offline • Time consuming • Excellent data quality • PD, Withstand, Tan Delta IEEE 400.3 Guide to field PD testing of shielded power cable • It’s a guide, not a standard! • It does not conflict with or support IEC 60270 • It discusses online and offline testing
IEC 60270 IEC 60270 Edition 3.0, 2000 • Direct connection only • Defines measurement circuit • Defines measurement technique • Defines calibration pulse generator • Measures PD in picoColoumbs (1 picoColoumb = 1 uA for 1 uS) Annex D – Use of RF meters for PD detection Annex F – Non-Electrical methods of PD detection (Acoustic, Visual, Chemical)
IEC 60270 & IEEE 4000 test equipment
Invasive versus Non- invasive detection techniques
Invasive - Offline Invasive methods require taking an outage to effect the test. Effectively this includes all direct connected test gear • All forms of offline testing are by definition invasive • VLF PD cable testing requires the cable to removed from service for 3-4 hours to test • Tan-Delta and other cable test methods require removing the cable from service • System Frequency PD cable testing requires getting truck mounted equipment on site and removing the cable from service • Permanently installed systems & sensors need to be de-energized to install
Electrical Tests Commonly Done - Offline •High Pot (potential) Tests for ability to withstand voltage for brief periods •Insulation Resistance (megger) Tests for resistance to ground that might cause leakage •Tan – Delta Tests for overall insulation health by comparing resistive and capacitive currents •IEEE-400 and IEC 60270 PD Tests for partial discharge offline (VLF, etc.)
Non-invasive - Online Also known as No-Outage testing, this type of testing requires no de- energizing of equipment and is safe to do around live voltages. • Ultrasonic/Acoustic testing – through louvers, vents, contact sensors, and parabolic dishes • TEV testing – Makes use of the Transient Earth Voltage phenomenon to safely detect internal discharge from outside cabinets • RFCT testing* - By attaching RFCT to cable ground straps, the PD current can be safely measured on live cables • RF Testing – Specifically designed directional and non-directional radio receivers can pickup the EMI generated by PD * installing RFCT on live cables requires opening the HV compartment and appropriate safety measures need to be followed
Practical Online PD Detection Methods Surface Discharge Activity • Ultrasonic Emission • TEV Detection - when high amplitude surface discharge • RFCT Detection of Current Pulse • RF Detection of EMI
Practical Online PD Detection Methods Internal Discharge Activity • Transient Earth Voltage (TEV) Detection • RFCT Detection of Current Pulse • RF Detection of EMI
Practical Online PD Detection Methods Cable Discharge Activity • RFCT Detection of Current Pulse • RF Detection of EMI – near terminations • TEV Detection – on outside of sheath • Ultrasonic Emission – only when very near surface
Direct Connected - Offline Testing
Very Low Frequency - VLF
VLF (for PD) Offline, Very Low Frequency IEC 60270 / IEEE 400.3 compliant test. Requires an outage and cable to be disconnected on both ends. To cable under test To shield of cable under test HV source Coupling Cap Filter
Offline PD Testing VLF, .01-1 Hz, Resonant AC (VLF is by far the most prevalent at medium voltage) Cable under test Cable Shield Defect AC Voltage Source Filter Coupling Capacitor Measuring Instrument Measuring Impedance Source Impedance
Offline PD Testing HF Current flow due to defect flashover Cable under test Cable Shield Defect Pure AC Voltage Source Filter Coupling Capacitor Measuring Instrument Measuring Impedance Source Impedance Current pulse A Voltage pulses at A
Direct Connect - PDIV / PDEV PDIV – PD Inception voltage PDEV – PD Extinguish voltage PDIV 16KV PDEV 13KV LINE 11KV PDIV 16KV LINE 11KV PDEV 10KV PD might start with a transient but won’t continue PD might start with a transient but won’t stop
35 Offline Test Equipment - Test Van Detector filter (allows LV detection lead to be connected to HV Supply and filters Hz) Test bushings VLF generator Transformer
Portable Unit -Approximately 500lbs
Direct Connected Offline Testing – Tan Delta
Tan Delta Tan Delta is a measurement of the loss angle or dissipation factor. Effectively, it is measuring the ratio of the capacitance and resistance in a cable In a perfect cable there would be no IR and the arrow A would be straight up. As the cable ages and gets water trees and electrical trees, resistance through the insulation creeps in. This causes IR and the angle increases.
Tan Delta Typical set up To cable under test To shield of cable
Online systems
Surface Discharge - Ultrasonic Emission
Ultrasonic Survey (Practical Considerations) •Influenced by environment (e.g. temperature, humidity, pollution). •When monitoring ultrasonically the environmental conditions (%RH and Temperature) should also be monitored •Discharge has a distinctive crackling noise. •Often intermittent, particularly during early stages. •Severity of discharge is not necessarily related to noise amplitude.
Environmental Factors • Moisture in air will play a significant role in whether discharge is active • When monitoring ultrasonically the environmental conditions (%RH and Temperature) should also be monitored 0 10 20 30 40 50 60 70 80 90 100 29/03/2005 00:00 03/04/2005 00:00 08/04/2005 00:00 13/04/2005 00:00 18/04/2005 00:00 23/04/2005 00:00 28/04/2005 00:00 03/05/2005 00:00 08/05/2005 00:00 13/05/2005 00:00 Date %RH, Temperature 0 1 2 3 4 5 6 7 8 9 10 Level of Ultrasonic Activity °C %RH Ultrasonic Ultrasonic Level Relative Humidity
< 6 Good background No observable/measurable deterioration 7 - 10 Fair Very slight fizzing only just above the background Minor Deterioration which requires no specific action 11 - 20 Poor Heavy fizzing or crackling Moderate Deterioration Item can be returned to service. Reinspect in 30 days. > 20 Action Required Spitting or sparking or heard with the naked ear Serious Deterioration Item cannot be returned to service without shut down or engineering advise Ultra dB Category Comments Ultrasonic Interpretation
Ultrasonic Sensors •Four different sensors are available for ultrasonic measurements •Built in Sensor – for general purpose airborne ultrasonic measurements •Flexible Sensor – for general purpose measurements that are harder to reach •UltraDish – Focuses sound energy for making measurements from a greater distance •Contact Sensor – for making measurements when there isn’t an air path from the source to the sensor
Discharge noise can be picked up Outside gear via louvers in cabinet • Measurement relies on an air path out of the switchgear • Types of air paths – Vents / Louvers – CB Bushings / HV spouts – Gaps around panel joints – Bolt holes Ultrasonic Detection
• Measurement relies on an air path out of the switchgear • When there’s no air path? – Contact sensor turns panel into sensor – Designed to work though cabinet metalwork, no direct air path needed Contact probe Designed to work though cabinet metalwork, no direct air path needed Ultrasonic Detection
• Technician takes a minute or two at each cubicle • Listens to audio via headphones • Watches display for patterns • Moves the probes along each air gap Ultrasonic Detection
Internal Discharge – TEV Detection
50 Transient Earth Voltage (TEV) Identification •Identified over 30 years ago •Measurement bandwidth 2 – 80 MHz •TEV pulse rise time was found to be circa 5ns •3dB Bandwidth = (0.35 / rise time). •Therefore for 5ns, bandwidth = (0.35 / 5) GHz, i.e. 70 MHz
51 Internal Partial Discharge Effect 1 (Current pulse - TEV) HV BUSBAR PARTIAL DISCHARGE SITE JOINT/GASKET HV BUSBAR HIGH FREQUENCY PULSE TO METALWORK VIA CAPACITANCE OF INSULATOR TEV RESULTS DUE TO IMPEDANCE OF GROUNDING MEASURING PROBE PULSE TRAVELS VIA SKIN EFFECT At HF, PD currents are constrained to flow in a thin layer on the surface of conductor. Skin depth in mild steel at 100MHz 0.5um
52 Internal Partial Discharge Effect 2 (EM Wave) This effect is usually less than the current pulse unless the PD is phase to phase! HV BUSBAR PARTIAL DISCHARGE SITE JOINT/GASKET HV BUSBAR EM wave incident to inside surfaces TEV RESULTS DUE TO IMPEDANCE OF GROUNDING MEASURING PROBE PULSE TRAVELS VIA SKIN EFFECT
53 Phase to Phase Partial Discharge (Current pulse – NO TEV) HV BUSBAR PARTIAL DISCHARGE JOINT/GASKET HV BUSBAR – Phase A HIGH FREQUENCY PULSE FROM PHASE TO ANOTHER. NO CURRENT PULSE ON METALWORK No TEV reading HV BUSBAR – Phase B HV BUSBAR – Phase C
54 Phase to Phase Partial Discharge (Current pulse – NO TEV) HV BUSBAR PARTIAL DISCHARGE JOINT/GASKET HV BUSBAR – Phase A NO CURRENT PULSE ON METALWORK HV BUSBAR – Phase B HV BUSBAR – Phase C EM wave incident to inside surfaces
55 Partial Discharge TEV Interpretation Probable Internal No Internal Significant Discharging Possible Surface Discharging Probable Background Interference Probable Floating Metal Bad Conn
• Technician takes a minute or two at each cubicle • Places TEV probe firmly against panel • Watches display for patterns TEV Detection
PD in resin core CT Channel cut through resin by discharge Cause – Manufacturing Defect (Void in resin)
Surface Discharge and Internal Discharge Differences Internal PD External PD Not affected by Humidity Affected by Humidity 0.5-6 Pulses per Cycle 6-30 Pulses per Cycle Rarely Audible Often Audible Detected best by TEV Detected best by Ultrasonic Hold UltraTEV against Ground or Metalwork Hold UltraTEV at airgaps of enclosures or point UltraDish at Elbows, T’s, or splices.
Cable Partial Discharge
Cable Partial Discharge Cable partial discharge is a classic example of local concentration of electrical stress. Cable terminations and splices have carefully designed components to distribute the electrical stresses equally. These components include semiconducting layers and stress cones. When these cones are not correct discharge occurs. Discharge can also occur where insulation is defective (holes, voids, damage) in mid-cable.
Equipotential Lines Voltage 0 V X kV 6X voltage drop Section through a homogenous insulator showing uniform electrical stress (equipotential) lines. A line indicates where the voltage potential is constant The same insulator with a void. The lower dielectric of the void causes a concentration of the electrical field through the void high enough to cause breakdown at working voltages
• RFCT placed on ground straps of cables • Test may do 1 or 3 phases at once • Test may run automatically or require operator involvement • Different filters and triggers are applied • Typically less than 10 minutes to get results Safety First Cable PD Detection
Shielded MV Cable Earth Ground Phase Reference Void (PD Site) Initial PD Current Pulse PD causes high current pulse to travel down shield to ground strap Instrument measures current pulse on ground strap Data Collection RFCT based testing of cables
Cable Partial Discharge Earth Ground Void (PD Site) Reflected PD Current Pulse Initial Pulse Reflected Pulse Current through ground strap results from PD down cable. Entire length of cable can be tested from one end Far end of cable Termination Ground Strap
65 Evaluation Scale Comments Color Code XLPE Cable XLPE Accessories PILC Cable PILC Accessories Discharge within “acceptable” limits. 0-250pC 0-500pC 0-2500pC 0-4000pC Some concern, more frequent monitoring recommended. 250-500pC 500- 2500pC 2500- 7000pC 4000- 10000pC Major concern, locate PD activity and repair or replace. >500pC >2500pC >7000pC >10000pC
66 Cable Partial Discharge Examples Treeing Voids / Carbonisation Erosion from PD Damage from flashover to screen
Cable Partial Discharge Terrible cut line causes electrical stress Partial Discharge causes erosion of insulation Stress causes partial discharge
Direct connected online systems
On-Line systems Direct connected online systems use permanently installed HV capacitors and current transformers to measure PD directly. • Periodic or 24x7 monitoring with alarming • Typically include remote communications • Can include humidity and load monitoring • Can be used for Rotating machines, Metal clad switchgear, MV/HV Cables, and Transformers
Direct connected monitoring systems
PD Couplers
72 Practical application of spot testing Insulation Conductor Sheath Earth Ground Ground Straps Data Collection Phase Reference Phase A Phase C Phase B
Data Analysis – VLF, Ultrasonic, TEV, Cable
74 Analyzing Data – Two crucial pieces of data Picking Milliamps of PD out of Kiloamps of current is not trivial. Two key pieces of information are vital
75 Analyzing Data – Phase Resolved Plots One sign of recognizable PD Activity is clustering of points on the phase resolve plot at a distance of 180º apart 1 Cycle wide (16.66 ms) Amplitude In pC Around 0 0
Partial Discharge tends to occur on the rising edge of the voltage sine wave. As such, PD impulses tend to be synchronized to the AC waveform and 180 degrees apart. 0 90 180 270 360 Phase Resolved plots show PD impulses on a power system cycle so groupings 180 degrees apart can be seen. Phase resolved plots are available for TEV, Ultrasonic, and Cable PD modes 180 Degrees Phase Resolved Plots
77 Analyzing Data – Waveforms A typical waveform from online Cable PD testing should have a large unipolar pulse indicating the discharge Very fast time base (40 uS) Amplitude In mA Around 0
3,000pC 0pC -3,000pC 0o 360o Activity – Actual PD Phase Plot
79 Non-PD Patterns – Random Noise Background Noise • Below is an example of background interference, which is characterized by random activity along the Phase Resolve plot. • Background interference may be caused by a number of sources including radio masts and DC light fittings.
80 Non-PD Patterns – VFD Noise Machine Noise • Data captured on circuits which have rotating machines operating on them will contain some machine noise • Machine noise is characterized by vertical lines spread across the phase resolved plot
Partial Discharge – Examples
A very large office building had full time partial discharge monitoring installed due to the critical nature of its operations. The monitor had ultrasonic sensing into each compartment from outside as shown below. The cables to the 33VK PTs were unshielded. They were installed in a way that passed Highpot testing. However, electrical field stress was ignored The monitor started recording ultrasonic energy when the humidity increased. This was monitored for several months before corrective action was taken. Every cable was damaged! PD in unshielded cables
Ultrasonic Trends over Time Ultrasonic reading from top of cabinet with PD Ultrasonic reading from bottom of cabinet with PD Ultrasonic reading from other 10 cabinets without PD Note large increase in 3 months and difference from other cabinets Ultrasonic Trend line
PD in unshielded cables Cause – Lack of stress control due to poor installation
The same office building had numerous 33KV terminations. The monitor started indicating TEV in one compartment. After several months, Ultrasonic became apparent as well The yellow phase termination suffered poor workmanship. It started as internal discharge (TEV) but progressed to surface discharge as the termination was eaten away. The final picture shows the fixed assembly Termination – Poor workmanship
PD in Shielded Cable Terminations Cause – Lack of stress control due to installation errors
Surface Discharge Activity Detected by Ultrasonics
PD in Switchgear Cause – Environment (Salt & Humidity)
PD in resin core CT Channel cut through resin by discharge Cause – Manufacturing Defect (Void in resin)
Surface Discharge Activity Detected by Ultrasonics
Cable failures – Case Studies
Cable failure example 1 Cable Type – PILC / XLPE Voltage – 11 KV Age – 1 Hour Failure Location – PICAS to XLPE Branch Adapter
Cable failure example 1 Proximate Cause – Incorrect positioning of adapter tubes Ultimate Cause – Workmanship Takeaways -Horrific workmanship -Numerous future failure points present 30 mm gap in insulation Only 1 shear bolt touching No putty in shear bolts Poorly cut tube
Cable failure example 2 Cable Type – XLPE Voltage – 33KV Age – 18 months Failure Location – Joint
Cable failure example 2 Proximate Cause – Not deburring connector Ultimate Cause – Workmanship Takeaways -Poor understanding of instructions -Lack of attention to detail -Lack of training Furrowing not removed Sand in joint Sharp edge of shear bolt
Cable failure example 3 Cable Type – XLPE Voltage – 11KV Age – 28 years Failure Location – Mid cable
Cable failure example 3 Proximate Cause – Moisture Ultimate Cause – Mechanical damage to sheath Takeaways -Mechanical damage to otherwise good cable -Replace waterlogged section -Better installation practices Trees Electrical Water
Cable failure example 4 Cable Type – PILC Voltage – 11KV Age – 47 Years Failure Location – Mid cable
Cable failure example 4 Proximate Cause – Partial Discharge Ultimate Cause – Age Takeaways - Not a bad lifespan - Partial discharge testing would have prevented unplanned failure - Replace Cable
Thank you EA Technology LLC 400 Morris Avenue Suite 240 Denville NJ 07834 Tim Erwin O 862 261 2759 C 862 222 3666 Email: Tim.erwin@eatechnologyusa.com Leading Edge Sales Jeffrey Pooranalingam C 403 471 5799 Email: Jeffreyp@leadingedgesales.com

More Related Content

PPTX
PPt on 220 kV substation
byIshank Ranjan
 
PPTX
Partial discharge testing
byDebojyoti Mukherjee
 
PPTX
Stability test of transformer
bySantu Mondal
 
PPTX
On load tap changer
bySourabh sharma
 
PPTX
switchgear and protection by vala kamlesh
byKamlesh Vala
 
PDF
Synchronous machines
bymichaeljmack
 
PPTX
Relays and its types - complete guide
bySlides Hub
 
PPT
Power transformer
byZunAib Ali
 
PPt on 220 kV substation
byIshank Ranjan
 
Partial discharge testing
byDebojyoti Mukherjee
 
Stability test of transformer
bySantu Mondal
 
On load tap changer
bySourabh sharma
 
switchgear and protection by vala kamlesh
byKamlesh Vala
 
Synchronous machines
bymichaeljmack
 
Relays and its types - complete guide
bySlides Hub
 
Power transformer
byZunAib Ali
 

What's hot

PPT
BUS BAR PROTECTION PPT BY:-R.K.PANDIT
byRAGHVENDRA KUMAR PANDIT
 
PPTX
132 kV uppcl
byAbrar Ahamed
 
PPTX
Switchgear presentation
byNadir Baloch
 
PPTX
Air circuit breaker (ACB) Low-Voltage Miduim-Voltage High Voltage
byRathana Lan
 
PPTX
Partial Discharge Test - Switchgear
byRajuGupta88
 
PPT
132 kv
bySourabh Bhattacharya
 
PPTX
Power Transformer Protection
byAng Sovann
 
PDF
Transformer differential protection
bymichaeljmack
 
PDF
Grounding,Earthing,Bonding
byKo Winnwe
 
PPTX
PPT on 33/11 sub-station uppcl
byVISHAL VERMA
 
PPT
Commissioning of Electrical Equipment or systems.ppt
byAlemayehuAsmare
 
PDF
Training at 132 kv substation
byTejveer Choudhary
 
PPTX
PPT Fault Analysis
byAnkitkumaralwariya
 
PPTX
Training report on substation presentation
byKanahiya Lal
 
DOCX
Protection of power transformer
byRitesh Verma
 
PPTX
NGR & Zig-Zag Transformer.pptx
byMUHAMMAD TAHIR
 
PPTX
power line carrier communication
byLAVANYA d
 
PPTX
Ppt of ehv ac transmission
bySumit Kumar
 
PDF
Power transformer protection
bymichaeljmack
 
PPTX
Transformer protection
byDr. Selvarasu Ranganathan
 
BUS BAR PROTECTION PPT BY:-R.K.PANDIT
byRAGHVENDRA KUMAR PANDIT
 
132 kV uppcl
byAbrar Ahamed
 
Switchgear presentation
byNadir Baloch
 
Air circuit breaker (ACB) Low-Voltage Miduim-Voltage High Voltage
byRathana Lan
 
Partial Discharge Test - Switchgear
byRajuGupta88
 
132 kv
bySourabh Bhattacharya
 
Power Transformer Protection
byAng Sovann
 
Transformer differential protection
bymichaeljmack
 
Grounding,Earthing,Bonding
byKo Winnwe
 
PPT on 33/11 sub-station uppcl
byVISHAL VERMA
 
Commissioning of Electrical Equipment or systems.ppt
byAlemayehuAsmare
 
Training at 132 kv substation
byTejveer Choudhary
 
PPT Fault Analysis
byAnkitkumaralwariya
 
Training report on substation presentation
byKanahiya Lal
 
Protection of power transformer
byRitesh Verma
 
NGR & Zig-Zag Transformer.pptx
byMUHAMMAD TAHIR
 
power line carrier communication
byLAVANYA d
 
Ppt of ehv ac transmission
bySumit Kumar
 
Power transformer protection
bymichaeljmack
 
Transformer protection
byDr. Selvarasu Ranganathan
 

Similar to IEEE-Alberta_Partial-Discharge.pdf

PPTX
IEEE-Alberta_Partial-Discharge new high voltages .pptx
bypebiwahyudin
 
PDF
Introduction to partial discharge
byMike Coffey
 
PPT
Seminar on Partial Discharge detection methods
byHarshit Bhandari
 
PDF
40220140506001
byIAEME Publication
 
PDF
Guidelines for Unconventional Partial Discharge Measurement (CIGRE 444)
byAHMED MOHAMED HEGAB
 
PDF
IPEC Presentation - Partial discharge Pro .pdf
bywaely1983
 
PPTX
Presentation-Power-Cable-Condition-Assessment
byEddy Fernando Queca Cadiz
 
PDF
Electrical condition monitoring part 2
byVincent Wedelich, PE MBA
 
PPTX
Partial Discharge Detection Products by EA Technology
byRyan McFallo
 
PDF
Descarga Parcial de Cables - Conferencia Virtual
byTRANSEQUIPOS S.A.
 
PPT
IQ_Partial_Discharge_Presentation_complete.ppt
byEddy Fernando Queca Cadiz
 
PPT
IQ_Partial_Discharge_Presentation.ppt
byssuserf6b378
 
PDF
Deis talk-nov-2014-revised
bySeverin A Eskeland
 
PDF
IRJET - A Review of an Investigation of Partial Discharge Sources and Loc...
byIRJET Journal
 
PDF
Nidec asi service partial discharge basic diagnostic
byNidec Corporation
 
PDF
Electrical Condition monitoring part 1
byVincent Wedelich, PE MBA
 
PDF
ipec mtekpro joint venture technology for testing and measuring instruments
byShaileshSingh671979
 
PDF
PD_Presentation_1.pdf
bymadivala nagaraja
 
PDF
Comparison of Different Voltage Waveforms for Cable PD Testing.pdf
byAliNaderian2
 
PDF
The benefits of pd monitoring Ben Jones
byNSW Environment and Planning
 
IEEE-Alberta_Partial-Discharge new high voltages .pptx
bypebiwahyudin
 
Introduction to partial discharge
byMike Coffey
 
Seminar on Partial Discharge detection methods
byHarshit Bhandari
 
40220140506001
byIAEME Publication
 
Guidelines for Unconventional Partial Discharge Measurement (CIGRE 444)
byAHMED MOHAMED HEGAB
 
IPEC Presentation - Partial discharge Pro .pdf
bywaely1983
 
Presentation-Power-Cable-Condition-Assessment
byEddy Fernando Queca Cadiz
 
Electrical condition monitoring part 2
byVincent Wedelich, PE MBA
 
Partial Discharge Detection Products by EA Technology
byRyan McFallo
 
Descarga Parcial de Cables - Conferencia Virtual
byTRANSEQUIPOS S.A.
 
IQ_Partial_Discharge_Presentation_complete.ppt
byEddy Fernando Queca Cadiz
 
IQ_Partial_Discharge_Presentation.ppt
byssuserf6b378
 
Deis talk-nov-2014-revised
bySeverin A Eskeland
 
IRJET - A Review of an Investigation of Partial Discharge Sources and Loc...
byIRJET Journal
 
Nidec asi service partial discharge basic diagnostic
byNidec Corporation
 
Electrical Condition monitoring part 1
byVincent Wedelich, PE MBA
 
ipec mtekpro joint venture technology for testing and measuring instruments
byShaileshSingh671979
 
PD_Presentation_1.pdf
bymadivala nagaraja
 
Comparison of Different Voltage Waveforms for Cable PD Testing.pdf
byAliNaderian2
 
The benefits of pd monitoring Ben Jones
byNSW Environment and Planning
 

Recently uploaded

PDF
Timeless Modern Interiors- A Design Perspective by Kiara Parekh
byKiara Parekh - Interior Designing Expert in Melbourne
 
PPTX
Doors and Windows in Building Construction
byhelpersinghji
 
PPTX
3 Phase Alternators in basic electric and electronic devices.pptx
byJemimaA1
 
PPTX
Digital Creation in 2026: The Future of Creativity, Content, and Technology
byemailanil07
 
PDF
Cross-Platform Development for Business Infographic (1).pdf
byjamesandersonuk40
 
PDF
CASE STUDY 3 1.pdfHHTGTGTGGGGGGGGGGGDGGFGGGGG
bykumarvragava
 
PDF
How to Shortlist the Right App Development Partner.pdf
byjamesandersonuk40
 
PPTX
Basic design minimalistic and useful for school projects and office presentat...
byankitsing73as
 
PDF
Buy Facebook Ads Accounts_ the Backbone of Social Advertising in 2025.pdf
bymarketing
 
PPTX
GATE-ALL-AROUND Tunneling Field Effect Transistor .pptx
bysaimakhoso1848
 
PDF
Architectural and interior designing in Virudhunagar
byAmar Dexign scape
 
PDF
B.6.0_2025-08-27_EASA_AI_Days_Slideware_day1_afternoon.pdf
byxusteven20
 
PDF
literature case study of museo do amanha
bymathewjohnmj18
 
PDF
Nilesh Mathur NID_Thesis 2025 ( Machphysolutions: Insulinsure_IIT Delhi )
byNileshMathur6
 
PPTX
AI_Presentation_About Artificial Inteligence
bymuharrammijlasmajils
 
PPT
Mortar important materials for construction
byMaheshRamteke3
 
PPTX
Website Designing in digital marketing..
bynadipallisruthi
 
PDF
LAYOUT dapur mbg sesuai dengan juklak dan juknis
bysugiyono37
 
PDF
The Future of Cross-Platform Development.pdf
byjamesandersonuk40
 
PPTX
How to Create Modern Scandinavian Décor at Home.pptx
byLeeMai12
 
Timeless Modern Interiors- A Design Perspective by Kiara Parekh
byKiara Parekh - Interior Designing Expert in Melbourne
 
Doors and Windows in Building Construction
byhelpersinghji
 
3 Phase Alternators in basic electric and electronic devices.pptx
byJemimaA1
 
Digital Creation in 2026: The Future of Creativity, Content, and Technology
byemailanil07
 
Cross-Platform Development for Business Infographic (1).pdf
byjamesandersonuk40
 
CASE STUDY 3 1.pdfHHTGTGTGGGGGGGGGGGDGGFGGGGG
bykumarvragava
 
How to Shortlist the Right App Development Partner.pdf
byjamesandersonuk40
 
Basic design minimalistic and useful for school projects and office presentat...
byankitsing73as
 
Buy Facebook Ads Accounts_ the Backbone of Social Advertising in 2025.pdf
bymarketing
 
GATE-ALL-AROUND Tunneling Field Effect Transistor .pptx
bysaimakhoso1848
 
Architectural and interior designing in Virudhunagar
byAmar Dexign scape
 
B.6.0_2025-08-27_EASA_AI_Days_Slideware_day1_afternoon.pdf
byxusteven20
 
literature case study of museo do amanha
bymathewjohnmj18
 
Nilesh Mathur NID_Thesis 2025 ( Machphysolutions: Insulinsure_IIT Delhi )
byNileshMathur6
 
AI_Presentation_About Artificial Inteligence
bymuharrammijlasmajils
 
Mortar important materials for construction
byMaheshRamteke3
 
Website Designing in digital marketing..
bynadipallisruthi
 
LAYOUT dapur mbg sesuai dengan juklak dan juknis
bysugiyono37
 
The Future of Cross-Platform Development.pdf
byjamesandersonuk40
 
How to Create Modern Scandinavian Décor at Home.pptx
byLeeMai12
 

IEEE-Alberta_Partial-Discharge.pdf

  • 1.
    Introduction to PartialDischarge (Causes, Effects, and Detection) Presented by: Tim Erwin National Sales Manager O 862 261 2759 C 862 222 3666 Email: Tim.erwin@eatechnologyusa.com
  • 2.
    EA Technology History& Values • Originally established as R&D center for the UK Electricity Industry (essentially EA Technology was the EPRI of the UK) in the late 1960’s. Privatized in the late 1990s. • Provides research, strategic engineering consultancy, HV asset condition assessment services, specialized instrumentation, and Asset Management Software and Consulting. • Instrumental in the development of PAS-55 and ISO-55000 • 100% employee owned and have provided products and service in 92 countries around the world EA Technology Capenhurst UK EA Technology LLC Denville, NJ - USA
  • 3.
    Partial Discharge –What is it and why do we care?
  • 4.
  • 5.
    PD failure process •Multiple causes • Starts small • ALWAYS gets worse • Leads to FLASHOVER What is Partial Discharge? PD is the inability of a portion of the insulation to withstand the electric field applied to it
  • 6.
    Partial Discharge (PD) Thekey to OUTAGE PREVENTION •3.3kV to 769kV •Indoor Metal clad switchgear cubicles •Indoor and Outdoor Insulators •Transformer Cable Boxes •MV & HV Cables, Terminations & Underground Vaults •Transformers •SF6 GIS / Oil Filled / Air Insulated Where can it occur?
  • 7.
    Partial Discharge -A flashover of part of the insulation system due to a localized electric field greater than the dielectric withstand capability of that part where the overall insulation system remains capable of withstanding the applied electrical field. Void Ground Conductor V withstand of C2 < applied field V withstand of C1&C3 > applied field 9 What is Partial Discharge (PD)? One effect of this flashover is a high frequency current pulse that travels through the capacitance of the insulation (C1 & C3) HF Current Pulse C1 C2 C3
  • 8.
    Equipotential Lines Voltage 0 V XkV 6X voltage drop Section through a homogenous insulator showing uniform electrical stress (equipotential) lines. A line indicates where the voltage potential is constant The same insulator with a void. The lower dielectric of the void causes a concentration of the electrical field through the void high enough to cause breakdown at working voltages
  • 9.
    11 Products of PartialDischarge Partial discharge breakdown of insulation produces: Light, Heat, Smell, Sound, Electromagnetic Waves, and an HF Electric Current Electric TEV I
  • 10.
    12 Products of PartialDischarge Partial discharge breakdown of insulation produces: Light, Heat, Smell, Sound, Electromagnetic Waves, and an HF Electric Current + Water Nitric Acid Electric TEV How does PD damage insulation? I
  • 11.
    UK utility undertooka two year evaluation of RFCT based on-line testing that performed a PD condition based assessment of 191 33KV cables on their network over a two year period. 84% rated GREEN (no problems) >2% of those failed within 2 years 7% rated Amber (no problems) <21% of those failed within 2 years 7% rated RED (no problems) <40% of those failed within 2 years CABLE TESTING Field Example
  • 12.
    Types of PD •Internaldischarges occurring in defects, voids or cavities within solid insulation •Surface discharges occurring across the insulation surface •Contact discharge occurs on floating metal in high field conditions •Corona discharge occurring in gaseous dielectrics in the presence of inhomogeneous fields
  • 13.
    • Internal Dischargeoccurs in all types of insulation as a result of defects, voids or cavities within solid insulation, also including oil and gas • Practical Non-Invasive method to detect Internal Partial Discharge Activity is to use Transient Earth Voltage (TEV) detection instruments. Partial Discharge (PD) Internal Partial Discharge
  • 14.
    • Surface dischargesoccurring across the insulation surface Causes treeing and tracking • Practical Non-Invasive method to detect Surface Partial Discharge Activity is to use Ultrasonic Emission detection instruments. Partial Discharge (PD) Surface PD
  • 15.
    Causes of PD •Surface contamination (lack of cleaning) • Workmanship (poor installation) • Material defects (manufacturing defects) • Improper application (wrong parts for the job) • Salt spray or Salt fog • Mechanical damage (during install or in service) • Age (electrical stress wears out insulation)
  • 16.
  • 17.
    IEEE 400 Series IEEE400 Guide to field testing shielded power cable • Cables only IEEE 400.1 Guide to testing shielded power cable with DC • Not for Aged XLP cable • Fine for PILC • i.e. IEEE 400.2 Guide to field testing shielded power cable with VLF • Offline • Time consuming • Excellent data quality • PD, Withstand, Tan Delta IEEE 400.3 Guide to field PD testing of shielded power cable • It’s a guide, not a standard! • It does not conflict with or support IEC 60270 • It discusses online and offline testing
  • 18.
    IEC 60270 IEC 60270Edition 3.0, 2000 • Direct connection only • Defines measurement circuit • Defines measurement technique • Defines calibration pulse generator • Measures PD in picoColoumbs (1 picoColoumb = 1 uA for 1 uS) Annex D – Use of RF meters for PD detection Annex F – Non-Electrical methods of PD detection (Acoustic, Visual, Chemical)
  • 19.
    IEC 60270 &IEEE 4000 test equipment
  • 20.
    Invasive versus Non- invasivedetection techniques
  • 21.
    Invasive - Offline Invasivemethods require taking an outage to effect the test. Effectively this includes all direct connected test gear • All forms of offline testing are by definition invasive • VLF PD cable testing requires the cable to removed from service for 3-4 hours to test • Tan-Delta and other cable test methods require removing the cable from service • System Frequency PD cable testing requires getting truck mounted equipment on site and removing the cable from service • Permanently installed systems & sensors need to be de-energized to install
  • 22.
    Electrical Tests CommonlyDone - Offline •High Pot (potential) Tests for ability to withstand voltage for brief periods •Insulation Resistance (megger) Tests for resistance to ground that might cause leakage •Tan – Delta Tests for overall insulation health by comparing resistive and capacitive currents •IEEE-400 and IEC 60270 PD Tests for partial discharge offline (VLF, etc.)
  • 23.
    Non-invasive - Online Alsoknown as No-Outage testing, this type of testing requires no de- energizing of equipment and is safe to do around live voltages. • Ultrasonic/Acoustic testing – through louvers, vents, contact sensors, and parabolic dishes • TEV testing – Makes use of the Transient Earth Voltage phenomenon to safely detect internal discharge from outside cabinets • RFCT testing* - By attaching RFCT to cable ground straps, the PD current can be safely measured on live cables • RF Testing – Specifically designed directional and non-directional radio receivers can pickup the EMI generated by PD * installing RFCT on live cables requires opening the HV compartment and appropriate safety measures need to be followed
  • 24.
    Practical Online PDDetection Methods Surface Discharge Activity • Ultrasonic Emission • TEV Detection - when high amplitude surface discharge • RFCT Detection of Current Pulse • RF Detection of EMI
  • 25.
    Practical Online PDDetection Methods Internal Discharge Activity • Transient Earth Voltage (TEV) Detection • RFCT Detection of Current Pulse • RF Detection of EMI
  • 26.
    Practical Online PDDetection Methods Cable Discharge Activity • RFCT Detection of Current Pulse • RF Detection of EMI – near terminations • TEV Detection – on outside of sheath • Ultrasonic Emission – only when very near surface
  • 27.
  • 28.
  • 29.
    VLF (for PD) Offline,Very Low Frequency IEC 60270 / IEEE 400.3 compliant test. Requires an outage and cable to be disconnected on both ends. To cable under test To shield of cable under test HV source Coupling Cap Filter
  • 30.
    Offline PD Testing VLF,.01-1 Hz, Resonant AC (VLF is by far the most prevalent at medium voltage) Cable under test Cable Shield Defect AC Voltage Source Filter Coupling Capacitor Measuring Instrument Measuring Impedance Source Impedance
  • 31.
    Offline PD Testing HFCurrent flow due to defect flashover Cable under test Cable Shield Defect Pure AC Voltage Source Filter Coupling Capacitor Measuring Instrument Measuring Impedance Source Impedance Current pulse A Voltage pulses at A
  • 32.
    Direct Connect -PDIV / PDEV PDIV – PD Inception voltage PDEV – PD Extinguish voltage PDIV 16KV PDEV 13KV LINE 11KV PDIV 16KV LINE 11KV PDEV 10KV PD might start with a transient but won’t continue PD might start with a transient but won’t stop
  • 33.
    35 Offline Test Equipment- Test Van Detector filter (allows LV detection lead to be connected to HV Supply and filters Hz) Test bushings VLF generator Transformer
  • 34.
  • 35.
  • 36.
    Tan Delta Tan Deltais a measurement of the loss angle or dissipation factor. Effectively, it is measuring the ratio of the capacitance and resistance in a cable In a perfect cable there would be no IR and the arrow A would be straight up. As the cable ages and gets water trees and electrical trees, resistance through the insulation creeps in. This causes IR and the angle increases.
  • 37.
    Tan Delta Typical setup To cable under test To shield of cable
  • 38.
  • 39.
  • 40.
    Ultrasonic Survey (Practical Considerations) •Influencedby environment (e.g. temperature, humidity, pollution). •When monitoring ultrasonically the environmental conditions (%RH and Temperature) should also be monitored •Discharge has a distinctive crackling noise. •Often intermittent, particularly during early stages. •Severity of discharge is not necessarily related to noise amplitude.
  • 41.
    Environmental Factors • Moisturein air will play a significant role in whether discharge is active • When monitoring ultrasonically the environmental conditions (%RH and Temperature) should also be monitored 0 10 20 30 40 50 60 70 80 90 100 29/03/2005 00:00 03/04/2005 00:00 08/04/2005 00:00 13/04/2005 00:00 18/04/2005 00:00 23/04/2005 00:00 28/04/2005 00:00 03/05/2005 00:00 08/05/2005 00:00 13/05/2005 00:00 Date %RH, Temperature 0 1 2 3 4 5 6 7 8 9 10 Level of Ultrasonic Activity °C %RH Ultrasonic Ultrasonic Level Relative Humidity
  • 42.
    < 6 Goodbackground No observable/measurable deterioration 7 - 10 Fair Very slight fizzing only just above the background Minor Deterioration which requires no specific action 11 - 20 Poor Heavy fizzing or crackling Moderate Deterioration Item can be returned to service. Reinspect in 30 days. > 20 Action Required Spitting or sparking or heard with the naked ear Serious Deterioration Item cannot be returned to service without shut down or engineering advise Ultra dB Category Comments Ultrasonic Interpretation
  • 43.
    Ultrasonic Sensors •Four differentsensors are available for ultrasonic measurements •Built in Sensor – for general purpose airborne ultrasonic measurements •Flexible Sensor – for general purpose measurements that are harder to reach •UltraDish – Focuses sound energy for making measurements from a greater distance •Contact Sensor – for making measurements when there isn’t an air path from the source to the sensor
  • 44.
    Discharge noise canbe picked up Outside gear via louvers in cabinet • Measurement relies on an air path out of the switchgear • Types of air paths – Vents / Louvers – CB Bushings / HV spouts – Gaps around panel joints – Bolt holes Ultrasonic Detection
  • 45.
    • Measurement relieson an air path out of the switchgear • When there’s no air path? – Contact sensor turns panel into sensor – Designed to work though cabinet metalwork, no direct air path needed Contact probe Designed to work though cabinet metalwork, no direct air path needed Ultrasonic Detection
  • 46.
    • Technician takesa minute or two at each cubicle • Listens to audio via headphones • Watches display for patterns • Moves the probes along each air gap Ultrasonic Detection
  • 47.
  • 48.
    50 Transient Earth Voltage(TEV) Identification •Identified over 30 years ago •Measurement bandwidth 2 – 80 MHz •TEV pulse rise time was found to be circa 5ns •3dB Bandwidth = (0.35 / rise time). •Therefore for 5ns, bandwidth = (0.35 / 5) GHz, i.e. 70 MHz
  • 49.
    51 Internal Partial DischargeEffect 1 (Current pulse - TEV) HV BUSBAR PARTIAL DISCHARGE SITE JOINT/GASKET HV BUSBAR HIGH FREQUENCY PULSE TO METALWORK VIA CAPACITANCE OF INSULATOR TEV RESULTS DUE TO IMPEDANCE OF GROUNDING MEASURING PROBE PULSE TRAVELS VIA SKIN EFFECT At HF, PD currents are constrained to flow in a thin layer on the surface of conductor. Skin depth in mild steel at 100MHz 0.5um
  • 50.
    52 Internal Partial DischargeEffect 2 (EM Wave) This effect is usually less than the current pulse unless the PD is phase to phase! HV BUSBAR PARTIAL DISCHARGE SITE JOINT/GASKET HV BUSBAR EM wave incident to inside surfaces TEV RESULTS DUE TO IMPEDANCE OF GROUNDING MEASURING PROBE PULSE TRAVELS VIA SKIN EFFECT
  • 51.
    53 Phase to PhasePartial Discharge (Current pulse – NO TEV) HV BUSBAR PARTIAL DISCHARGE JOINT/GASKET HV BUSBAR – Phase A HIGH FREQUENCY PULSE FROM PHASE TO ANOTHER. NO CURRENT PULSE ON METALWORK No TEV reading HV BUSBAR – Phase B HV BUSBAR – Phase C
  • 52.
    54 Phase to PhasePartial Discharge (Current pulse – NO TEV) HV BUSBAR PARTIAL DISCHARGE JOINT/GASKET HV BUSBAR – Phase A NO CURRENT PULSE ON METALWORK HV BUSBAR – Phase B HV BUSBAR – Phase C EM wave incident to inside surfaces
  • 53.
    55 Partial Discharge TEVInterpretation Probable Internal No Internal Significant Discharging Possible Surface Discharging Probable Background Interference Probable Floating Metal Bad Conn
  • 54.
    • Technician takesa minute or two at each cubicle • Places TEV probe firmly against panel • Watches display for patterns TEV Detection
  • 55.
    PD in resincore CT Channel cut through resin by discharge Cause – Manufacturing Defect (Void in resin)
  • 56.
    Surface Discharge andInternal Discharge Differences Internal PD External PD Not affected by Humidity Affected by Humidity 0.5-6 Pulses per Cycle 6-30 Pulses per Cycle Rarely Audible Often Audible Detected best by TEV Detected best by Ultrasonic Hold UltraTEV against Ground or Metalwork Hold UltraTEV at airgaps of enclosures or point UltraDish at Elbows, T’s, or splices.
  • 57.
  • 58.
    Cable Partial Discharge Cablepartial discharge is a classic example of local concentration of electrical stress. Cable terminations and splices have carefully designed components to distribute the electrical stresses equally. These components include semiconducting layers and stress cones. When these cones are not correct discharge occurs. Discharge can also occur where insulation is defective (holes, voids, damage) in mid-cable.
  • 59.
    Equipotential Lines Voltage 0 V XkV 6X voltage drop Section through a homogenous insulator showing uniform electrical stress (equipotential) lines. A line indicates where the voltage potential is constant The same insulator with a void. The lower dielectric of the void causes a concentration of the electrical field through the void high enough to cause breakdown at working voltages
  • 60.
    • RFCT placedon ground straps of cables • Test may do 1 or 3 phases at once • Test may run automatically or require operator involvement • Different filters and triggers are applied • Typically less than 10 minutes to get results Safety First Cable PD Detection
  • 61.
    Shielded MV Cable Earth Ground Phase Reference Void(PD Site) Initial PD Current Pulse PD causes high current pulse to travel down shield to ground strap Instrument measures current pulse on ground strap Data Collection RFCT based testing of cables
  • 62.
    Cable Partial Discharge Earth Ground Void(PD Site) Reflected PD Current Pulse Initial Pulse Reflected Pulse Current through ground strap results from PD down cable. Entire length of cable can be tested from one end Far end of cable Termination Ground Strap
  • 63.
    65 Evaluation Scale Comments Color Code XLPE Cable XLPE Accessories PILC Cable PILC Accessories Discharge within“acceptable” limits. 0-250pC 0-500pC 0-2500pC 0-4000pC Some concern, more frequent monitoring recommended. 250-500pC 500- 2500pC 2500- 7000pC 4000- 10000pC Major concern, locate PD activity and repair or replace. >500pC >2500pC >7000pC >10000pC
  • 64.
    66 Cable Partial DischargeExamples Treeing Voids / Carbonisation Erosion from PD Damage from flashover to screen
  • 65.
    Cable Partial Discharge Terriblecut line causes electrical stress Partial Discharge causes erosion of insulation Stress causes partial discharge
  • 66.
  • 67.
    On-Line systems Direct connectedonline systems use permanently installed HV capacitors and current transformers to measure PD directly. • Periodic or 24x7 monitoring with alarming • Typically include remote communications • Can include humidity and load monitoring • Can be used for Rotating machines, Metal clad switchgear, MV/HV Cables, and Transformers
  • 68.
  • 69.
  • 70.
    72 Practical application ofspot testing Insulation Conductor Sheath Earth Ground Ground Straps Data Collection Phase Reference Phase A Phase C Phase B
  • 71.
    Data Analysis –VLF, Ultrasonic, TEV, Cable
  • 72.
    74 Analyzing Data –Two crucial pieces of data Picking Milliamps of PD out of Kiloamps of current is not trivial. Two key pieces of information are vital
  • 73.
    75 Analyzing Data –Phase Resolved Plots One sign of recognizable PD Activity is clustering of points on the phase resolve plot at a distance of 180º apart 1 Cycle wide (16.66 ms) Amplitude In pC Around 0 0
  • 74.
    Partial Discharge tendsto occur on the rising edge of the voltage sine wave. As such, PD impulses tend to be synchronized to the AC waveform and 180 degrees apart. 0 90 180 270 360 Phase Resolved plots show PD impulses on a power system cycle so groupings 180 degrees apart can be seen. Phase resolved plots are available for TEV, Ultrasonic, and Cable PD modes 180 Degrees Phase Resolved Plots
  • 75.
    77 Analyzing Data –Waveforms A typical waveform from online Cable PD testing should have a large unipolar pulse indicating the discharge Very fast time base (40 uS) Amplitude In mA Around 0
  • 76.
  • 77.
    79 Non-PD Patterns –Random Noise Background Noise • Below is an example of background interference, which is characterized by random activity along the Phase Resolve plot. • Background interference may be caused by a number of sources including radio masts and DC light fittings.
  • 78.
    80 Non-PD Patterns –VFD Noise Machine Noise • Data captured on circuits which have rotating machines operating on them will contain some machine noise • Machine noise is characterized by vertical lines spread across the phase resolved plot
  • 79.
  • 80.
    A very largeoffice building had full time partial discharge monitoring installed due to the critical nature of its operations. The monitor had ultrasonic sensing into each compartment from outside as shown below. The cables to the 33VK PTs were unshielded. They were installed in a way that passed Highpot testing. However, electrical field stress was ignored The monitor started recording ultrasonic energy when the humidity increased. This was monitored for several months before corrective action was taken. Every cable was damaged! PD in unshielded cables
  • 81.
    Ultrasonic Trends overTime Ultrasonic reading from top of cabinet with PD Ultrasonic reading from bottom of cabinet with PD Ultrasonic reading from other 10 cabinets without PD Note large increase in 3 months and difference from other cabinets Ultrasonic Trend line
  • 82.
    PD in unshieldedcables Cause – Lack of stress control due to poor installation
  • 83.
    The same officebuilding had numerous 33KV terminations. The monitor started indicating TEV in one compartment. After several months, Ultrasonic became apparent as well The yellow phase termination suffered poor workmanship. It started as internal discharge (TEV) but progressed to surface discharge as the termination was eaten away. The final picture shows the fixed assembly Termination – Poor workmanship
  • 84.
    PD in ShieldedCable Terminations Cause – Lack of stress control due to installation errors
  • 85.
    Surface Discharge ActivityDetected by Ultrasonics
  • 86.
    PD in Switchgear Cause– Environment (Salt & Humidity)
  • 87.
    PD in resincore CT Channel cut through resin by discharge Cause – Manufacturing Defect (Void in resin)
  • 88.
    Surface Discharge ActivityDetected by Ultrasonics
  • 89.
    Cable failures –Case Studies
  • 90.
    Cable failure example1 Cable Type – PILC / XLPE Voltage – 11 KV Age – 1 Hour Failure Location – PICAS to XLPE Branch Adapter
  • 91.
    Cable failure example1 Proximate Cause – Incorrect positioning of adapter tubes Ultimate Cause – Workmanship Takeaways -Horrific workmanship -Numerous future failure points present 30 mm gap in insulation Only 1 shear bolt touching No putty in shear bolts Poorly cut tube
  • 92.
    Cable failure example2 Cable Type – XLPE Voltage – 33KV Age – 18 months Failure Location – Joint
  • 93.
    Cable failure example2 Proximate Cause – Not deburring connector Ultimate Cause – Workmanship Takeaways -Poor understanding of instructions -Lack of attention to detail -Lack of training Furrowing not removed Sand in joint Sharp edge of shear bolt
  • 94.
    Cable failure example3 Cable Type – XLPE Voltage – 11KV Age – 28 years Failure Location – Mid cable
  • 95.
    Cable failure example3 Proximate Cause – Moisture Ultimate Cause – Mechanical damage to sheath Takeaways -Mechanical damage to otherwise good cable -Replace waterlogged section -Better installation practices Trees Electrical Water
  • 96.
    Cable failure example4 Cable Type – PILC Voltage – 11KV Age – 47 Years Failure Location – Mid cable
  • 97.
    Cable failure example4 Proximate Cause – Partial Discharge Ultimate Cause – Age Takeaways - Not a bad lifespan - Partial discharge testing would have prevented unplanned failure - Replace Cable
  • 98.
    Thank you EA TechnologyLLC 400 Morris Avenue Suite 240 Denville NJ 07834 Tim Erwin O 862 261 2759 C 862 222 3666 Email: Tim.erwin@eatechnologyusa.com Leading Edge Sales Jeffrey Pooranalingam C 403 471 5799 Email: Jeffreyp@leadingedgesales.com