Upload
molly-macdonald
View
247
Download
10
Tags:
Embed Size (px)
Citation preview
DOWDING & MILLS
Condition Monitoring Of High Voltage Condition Monitoring Of High Voltage
MachinesMachines
By The Analysis ofBy The Analysis of
Electrical Partial DischargesElectrical Partial Discharges
22 April 0422 April 04
Dino KouadriaDino KouadriaPhD MSc BEng CEng MIEE MIEEEPhD MSc BEng CEng MIEE MIEEE
DOWDING & MILLS
CONTENTCONTENT
What is Partial Discharge (PD) Analysis.What is Partial Discharge (PD) Analysis.
Stator winding Common FaultsStator winding Common Faults..
Basics Of Why & How To Measure PD.Basics Of Why & How To Measure PD.
Case Studies.Case Studies.
Open Discussions.Open Discussions.
DOWDING & MILLS
It is an It is an electricalelectrical condition monitoring condition monitoring
technique.technique.
Used to assess the condition of hv Used to assess the condition of hv
insulationinsulation
Wider applications Wider applications
static static itemsitems i.E. Switchgear, cables i.E. Switchgear, cables
transformers, etc. transformers, etc.
Dynamic items i.E. Dynamic items i.E. Electrical machinesElectrical machines
What is Partial Discharges AnalysisWhat is Partial Discharges Analysis
DOWDING & MILLS
Apply to HV motors & generators (>5kv)Apply to HV motors & generators (>5kv)
Online & off line tests.Online & off line tests.
Predominantly Predominantly on-line testson-line tests - - no shut no shut
downdown & & testtestss under under
normal stress normal stress condition.condition.
PDs Analysis On HV WindingsPDs Analysis On HV Windings
DOWDING & MILLS
Assess the current & development in Assess the current & development in
condition of the condition of the
windingswindings
Maintenance Maintenance planning planning based on machines’ based on machines’
health.health.
Elimination of unwanted/unexpected Elimination of unwanted/unexpected
shutdowns.shutdowns.
Assistance in Assistance in targeting maintenance effort targeting maintenance effort
effectivelyeffectively..
LeaveLeave MaintainMaintain
ReplaceReplace
PDs Analysis On HV WindingsPDs Analysis On HV Windings
DOWDING & MILLS
Why Do HV Stators Fail?
Failures due to windings’ insulation failureFailures due to windings’ insulation failure caused caused
by the combinedby the combined
electrical, thermal, environmental and electrical, thermal, environmental and mechanicalmechanical
stress factors.stress factors.
Most common causes in modern insulation are Most common causes in modern insulation are
mechanically induced defects i.E. mechanically induced defects i.E. Loose wedgesLoose wedges, ,
erosion due to erosion due to bar vibrationbar vibration etc. - etc. - Short time Short time
degradation process.degradation process.
Discharge between phases due to cracks / low Discharge between phases due to cracks / low
spacingspacing
Contamination of end windings.Contamination of end windings.
Others: internal voids, insulation ageing, Others: internal voids, insulation ageing,
delamination.delamination.
Electrical partial dischargesElectrical partial discharges
DOWDING & MILLS
Regardless of the type of defects, they Regardless of the type of defects, they
all result in the generation of all result in the generation of
Electrical partial discharges.Electrical partial discharges.
So what are partial discharges?So what are partial discharges?
DOWDING & MILLS
What is a partial dischargeLocal breakdown that short circuits part of theLocal breakdown that short circuits part of the Insulation.Insulation.
Formation of corrosive ions, acids, nitrogen oxides, ozone.Formation of corrosive ions, acids, nitrogen oxides, ozone.
Detected using Detected using of chemical sensors for detection.of chemical sensors for detection.
Emission of light, sound & electromagnetic waves. Emission of light, sound & electromagnetic waves.
Detected using Detected using ultrasonic devices, antennae, cameras..ultrasonic devices, antennae, cameras..
Injection of high frequency current pulses.Injection of high frequency current pulses.
Detected using Detected using electrical partial discharges measurement electrical partial discharges measurement
(pd).(pd).
Vs = Vs = AApplied voltagepplied voltage
CavityCavityVVss
DOWDING & MILLS
-
+ +
Patterns & location of pulses within AC cyclePatterns & location of pulses within AC cycleIs the key in defects identificationIs the key in defects identification
Partial Discharges Basic Partial Discharges Basic Theory Theory
DOWDING & MILLS
Importance Of Monitoring PDs Importance Of Monitoring PDs
Different defects produce different PD patterns.Different defects produce different PD patterns.
Complex PD patterns are produced when multiple defects Complex PD patterns are produced when multiple defects
are present.are present.
Failures are due to localized defects.Failures are due to localized defects.
PD pattern development over time represents developing PD pattern development over time represents developing
degradation processes.degradation processes.
Provide an early warning of potential problemsProvide an early warning of potential problems
DOWDING & MILLS
Discharge Discharge levelslevels
TimeTime
3 – 6 months3 – 6 months ?? Years?? Years
CuringCuring Process Process Fabrication Defects
Contamination
Mechanical failure
Partial discharge monitoring over a machine Partial discharge monitoring over a machine life cyclelife cycle
Repair/action required
DOWDING & MILLS
PD DetectionPD Detection
Two main type of permanently installed sensors.Two main type of permanently installed sensors.
Capacitive couplers first developed in north Capacitive couplers first developed in north
america. Main users power industry.america. Main users power industry.
Rogowski coils first developed for the north sea Rogowski coils first developed for the north sea
oil industry. oil industry.
North sea oil industry – mainly Rogowski coilsNorth sea oil industry – mainly Rogowski coils
Ease of Ease of installation: installation: no disconnection of supply no disconnection of supply
cables, cables, lessless installation installation timetime..
Atex certifiedAtex certified
DOWDING & MILLS
Rogowski Coils: Typical InstallationRogowski Coils: Typical Installation
DOWDING & MILLS
Partial DischargePartial Discharge Analysis/Display Analysis/Display: Typical : Typical Cycle Cycle
DOWDING & MILLS
Partial Discharge Partial Discharge Analysis/DisplayAnalysis/Display: Total : Total Discharge ActivityDischarge Activity
DOWDING & MILLS
Partial Discharge Partial Discharge Analysis/DisplayAnalysis/Display: : Pulse Pulse Height AnalysisHeight Analysis
DOWDING & MILLS
CASE STUDIESCASE STUDIES
DOWDING & MILLS
Case studiesCase studies
1 Contamination on old pump motor 1 Contamination on old pump motor 11KV-11KV-3MW3MW
2 New motor manufacturing problem 2 New motor manufacturing problem 13.8KV-12MW13.8KV-12MW
3 Coil Movement old motor 3 Coil Movement old motor 6.6KV-9MW6.6KV-9MW
4 Plastics plant old motor high PD 4 Plastics plant old motor high PD 11KV-2.5MW11KV-2.5MW
DOWDING & MILLS
Total Discharge ActivityTotal Discharge Activity
3MW Pump Motor
DOWDING & MILLS
White power deposits clear White power deposits clear signs of discharge activitysigns of discharge activity
Typical Detected Faults Damage due to movement and contaminationTypical Detected Faults Damage due to movement and contamination3MW Pump Motor
DOWDING & MILLS
13.8 kV 12.7 MW Gas Compressor13.8 kV 12.7 MW Gas Compressor
DOWDING & MILLS
13.8 kV 12.7 MW Gas Compressor13.8 kV 12.7 MW Gas Compressor
0ver 70% of wedges loose or missing
DOWDING & MILLS
Typical Detected Faults Damage due to wedge movementTypical Detected Faults Damage due to wedge movement
13.8 kV 12.7 MW Gas Compressor13.8 kV 12.7 MW Gas Compressor
DOWDING & MILLS
Banded Discharge is Banded Discharge is
modulated which is due to modulated which is due to
coil movement .....coil movement .....
9MW Gas Compression Motor
DOWDING & MILLS
9MW Gas Compression Motor
DOWDING & MILLS
Good Coil Good Coil
Air Duct ImpressionsAir Duct Impressions
9MW Gas Compression Motor
DOWDING & MILLS
Damaged Coil
Lamination groves due to movement
Air Ducts (no abrasion)
9MW Gas Compression Motor
DOWDING & MILLS
Heavily Damaged Coil Due to impacting on slot bottom
9MW Gas Compression Motor
DOWDING & MILLS
2420KW 11kV ASEA synchronous compressor motor
DOWDING & MILLS
Detect any potential insulation problems.
The contribution of the different problems.
Location of problems within the winding.
Development in windings condition (through regular
monitoring)
Early detection allows scheduling of remedial work/repairs.
“Provide the maintenance engineer with the information to
make
The most cost effective decisions on planned maintenance”
Outcome of A PD Analysis SurveyOutcome of A PD Analysis Survey
DOWDING & MILLS
Partial Discharge AnalysisPartial Discharge Analysis
Not an exact Science.Not an exact Science.
Does not predict when plant is likely to Does not predict when plant is likely to
fail.fail.
BUTBUT will highlight which machines are will highlight which machines are
most likely to fail.most likely to fail.
Does not detectDoes not detect Inter-turn FaultsInter-turn Faults
More room for improvement in defect More room for improvement in defect
recognition.recognition.
Future development in insulation/motor Future development in insulation/motor
designs.designs.
DOWDING & MILLS
Condition Monitoring Of High Voltage Condition Monitoring Of High Voltage
MachinesMachines
By The Analysis ofBy The Analysis of
Electrical Partial DischargesElectrical Partial Discharges
22 April 0422 April 04
Dino KouadriaDino KouadriaPhD MSc BEng CEng MIEE MIEEEPhD MSc BEng CEng MIEE MIEEE