Presentation on theme: "Condition Monitoring Of High Voltage Machines By The Analysis of"— Presentation transcript:
1 Condition Monitoring Of High Voltage Machines By The Analysis of Electrical Partial Discharges22 April 04Dino KouadriaPhD MSc BEng CEng MIEE MIEEE
2 CONTENT What is Partial Discharge (PD) Analysis. Stator winding Common Faults.Basics Of Why & How To Measure PD.Case Studies.Open Discussions.
3 What is Partial Discharges Analysis It is an electrical condition monitoring technique.Used to assess the condition of hv insulationWider applicationsstatic items i.E. Switchgear, cables transformers, etc.Dynamic items i.E. Electrical machines
4 PDs Analysis On HV Windings Apply to HV motors & generators (>5kv)Online & off line tests.Predominantly on-line tests - no shut down & tests undernormal stress condition.
5 PDs Analysis On HV Windings Assess the current & development in condition of thewindingsMaintenance planning based on machines’ health.Elimination of unwanted/unexpected shutdowns.Assistance in targeting maintenance effort effectively.Leave Maintain Replace
6 Why Do HV Stators Fail?Failures due to windings’ insulation failure caused by the combinedelectrical, thermal, environmental and mechanical stress factors.Most common causes in modern insulation are mechanically induced defects i.E. Loose wedges, erosion due to bar vibration etc. - Short time degradation process.Discharge between phases due to cracks / low spacingContamination of end windings.Others: internal voids, insulation ageing, delamination.Electrical partial discharges
7 Electrical partial discharges. So what are partial discharges? Regardless of the type of defects, they all result in the generation ofElectrical partial discharges.So what are partial discharges?
8 What is a partial discharge Local breakdown that short circuits part of the Insulation.Vs = Applied voltageCavityVsFormation of corrosive ions, acids, nitrogen oxides, ozone.Detected using of chemical sensors for detection.Emission of light, sound & electromagnetic waves.Detected using ultrasonic devices, antennae, cameras..Injection of high frequency current pulses.Detected using electrical partial discharges measurement (pd).
9 Partial Discharges Basic Theory -+Patterns & location of pulses within AC cycleIs the key in defects identification
10 Importance Of Monitoring PDs Different defects produce different PD patterns.Complex PD patterns are produced when multiple defects are present.Failures are due to localized defects.PD pattern development over time represents developing degradation processes.Provide an early warning of potential problems
11 Partial discharge monitoring over a machine life cycle Discharge levelsRepair/action requiredCuring ProcessFabrication DefectsContaminationMechanical failure3 – 6 months?? YearsTime
12 North sea oil industry – mainly Rogowski coils PD DetectionTwo main type of permanently installed sensors.Capacitive couplers first developed in north america. Main users power industry.Rogowski coils first developed for the north sea oil industry.North sea oil industry – mainly Rogowski coilsEase of installation: no disconnection of supply cables, less installation time.Atex certified
18 Case studies 1 Contamination on old pump motor Case studies 1 Contamination on old pump motor 11KV-3MW 2 New motor manufacturing problem 13.8KV-12MW 3 Coil Movement old motor KV-9MW 4 Plastics plant old motor high PD 11KV-2.5MW
19 Total Discharge Activity 3MW Pump MotorTotal Discharge Activity
20 Typical Detected Faults Damage due to movement and contamination 3MW Pump MotorTypical Detected Faults Damage due to movement and contaminationWhite power deposits clearsigns of discharge activity
30 Outcome of A PD Analysis Survey 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 makeThe most cost effective decisions on planned maintenance”
31 Partial Discharge Analysis Not an exact Science.Does not predict when plant is likely to fail.BUT will highlight which machines are most likely to fail.Does not detect Inter-turn FaultsMore room for improvement in defect recognition.Future development in insulation/motor designs.
32 Condition Monitoring Of High Voltage Machines By The Analysis of Electrical Partial Discharges22 April 04Dino KouadriaPhD MSc BEng CEng MIEE MIEEE