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Condition Monitoring Of
Electrical Assets
Stephen Pierce
Condition Monitoring OfficerAGL Torrens Island Power Station
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Condition Monitoring Of Electrical Assets
What is condition monitoring.
Using various technologies to monitor the current performance of apiece of equipment to determine if it is operating within specifiedguidelines.
The results obtained from the monitoring along with previous resultscan give an indication to the life assessment of the equipment andassist in determining the nature of any abnormality.
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Condition Monitoring Of Electrical Assets
Types of condition monitoring.
Thermography Motor testing
Transformer oil analysis Battery testing
Ultrasonics
Vibration
Lube oil analysis
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Condition Monitoring Of Electrical Assets
Thermography inspectionsUsing infrared imaging equipment to capture the infrared radiationfrom a specific piece of equipment to determine if it is operatingwithin its normal performance specifications.
Switchgear and Control gear Assemblies (AS3439)
Terminals of load cables; 70C Temperature rise limit.
External covers; Metal, 30C Temperature rise limit.
Insulating, 40C Temperature rise limit.
Fuses (AS60269.1)Contacts tin plated; Spring, 60C Temperature rise limit.
Bolted; 65C Temperature rise limit.
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Condition Monitoring Of Electrical Assets
ThermographyInspecting the HT bushings on a 13.8/275kV 144 MVA step up transformer.
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Condition Monitoring Of Electrical Assets
ThermographyInspecting the HT bushings on a 13.8/275kV step up transformer.
14C
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Condition Monitoring Of Electrical Assets
Thermography13.8/6.6kV 7.5 MVA Transformer Cooling fins.Ambient temperature 13C, load on 6.6kV side was 455 amps.
31C
23C
16C
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Condition Monitoring Of Electrical Assets
Thermography220V DC system, from battery charger to the batteries and inverter.
Three diodes in parallel, load approximately 55 amps
26C
50C
25C
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Condition Monitoring Of Electrical Assets
Motor testingInsulation testing
Using the appropriate equipment to test the quality of the insulationfrom phase to earth and between phases to determine if it willwithstand the applied voltage.
415V Motors 1kV DC6.6kV Motors 5 kV DC
If conducting a one minute test, temperature correction should beapplied. Resistance changes with temperature. Select a basetemperature (20C) and correct readings to that for more reliableresults.
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Condition Monitoring Of Electrical Assets
Motor testingTesting the insulation on a 415V motor, windings to the frame.
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Condition Monitoring Of Electrical AssetsInsulation Resistance Correction Curve
0
1
2
3
4
5
6
7
8
9
0 5 10 15 20 25 30 35 40 45 50 55
Temperature
CorrectionFactor
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Condition Monitoring Of Electrical Assets
Motor testing
Stator Windings and Rotor
Checking for shorted turns within the windings or shorts between thewindings.
Checking for rotor faults (cracked rotor bars)
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Condition Monitoring Of Electrical Assets
Motor testingTesting the windings on a 415V motor, across a set of windings.
Alltest IV Pro 2000
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Condition Monitoring Of Electrical Assets
Motor testingTesting the rotor on a 415V motor, across a set of windings.
Alltest IV Pro 2000
Readings taken in inductance
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Condition Monitoring Of Electrical Assets
Motor testingTesting the rotor on a 415V motor.
A set of readings istaken across eachset of windings ateach 15of rotation
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Condition Monitoring Of Electrical Assets
Motor testing Rotor test (Alltest IV Pro 2000)
Rotor Test
14
14.5
15
15.5
16
16.5
17
0 50 100 150 200 250 300 350 400
Degrees
mH
A - B
A - C
B - C
Indicates damaged rotor
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Condition Monitoring Of Electrical Assets
Transformer oil analysis
Transformer oil samples are taken on a six or twelve monthly basisdepending on the criticality of the equipment.
Samples are taken for both dissolved gas analysis (DGA) and oilquality.
Samples are sent off site for analysis with reports supplied showingthe current results and the previous four results for trendingpurposes.
Suitability of results are obtained from a number of standards.IEC 60599 Mineral oil impregnated electrical equipment in service.
Guide to the interpretation of dissolved and free gases analysis.
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Condition Monitoring Of Electrical AssetsTransformer oil analysis
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Condition Monitoring Of Electrical Assets
Battery maintenance and testing
Battery testing is carried out as per the relevant Australian Standard.
Three different types of maintenance inspection.
Monthly
Quarterly (includes monthly)
Yearly (includes quarterly and monthly)
AS 2676.1 1992; Vented cells
AS 2676.2 1992; Sealed cells
Guide to the installation, maintenance, testing and replacement ofsecondary batteries in building
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Condition Monitoring Of Electrical Assets
Battery testingUsing a digital hydrometer, records specific gravity and temperature.
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Condition Monitoring Of Electrical Assets
Battery testingUsing an impedance tester, also records voltage,
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Condition Monitoring Of Electrical Assets
Battery testingResults of a routine test, showing, voltage, impedance and specific gravityfor each cell of a 110V battery bank.
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Condition Monitoring Of Electrical Assets
Ultrasonics The detection of sound above the 20kHz range.
This is in a range that is not audible to the human ear. Most humans
can hear between about 20Hz up to 20kHz
In the electrical area can be used to detect.
Corona (voltages above 1kV required for corona to be produced)
ArcingTracking
The type of sound recorded determines the type of electricaldisturbance.
Sound levels are recorded in a percentage or dB (depending onequipment). Levels can be trended to monitor for deterioration.
C diti M it i Of El t i l A t
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Condition Monitoring Of Electrical Assets
Ultrasonics
Listening to 275kV HT bushings on a transformer.
C diti M it i Of El t i l A t
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Condition Monitoring Of Electrical Assets
Ultrasonics
Listening to a 6.6kV circuit breaker.
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Condition Monitoring Of Electrical Assets
Vibration and lube oil analysis
Both vibration and oil analysis can provide information on the
condition of a bearing (oil lubricated bearings).
Vibration readings are taken in the horizontal, vertical and axialdirections.
Oil sampling results look for unacceptable levels of moisture,viscosity, wear metals, oil additives and particle count.
Abnormalities with oil are usually evident prior to detecting
abnormalities with vibration.
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Condition Monitoring Of Electrical Assets
Vibration and lube oil analysis
Vibration sensor pad
Oil sample point
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Condition Monitoring Of Electrical Assets
Thermography and Ultrasonics
Both are used as on line non contact methods of monitoringelectrical assets.
Can support each other and also each technology can providespecific information.
Thermography can not detect corona because it does not produceheat, ultrasonics can due to the noise produced by the electricaldischarge of the corona.
Thermography and ultrasonics testing are done together so the plantconditions are the same.
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Condition Monitoring Of Electrical Assets