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8/9/2019 3-Steve Pierce AGL Torrens Isl

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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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Types of condition monitoring.

Thermography Motor testing

Transformer oil analysis Battery testing

Ultrasonics

Vibration

Lube oil analysis


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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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ThermographyInspecting the HT bushings on a 13.8/275kV 144 MVA step up transformer.


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ThermographyInspecting the HT bushings on a 13.8/275kV step up transformer.

14C


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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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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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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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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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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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Motor testingTesting the windings on a 415V motor, across a set of windings.

Alltest IV Pro 2000


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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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Motor testingTesting the rotor on a 415V motor.

A set of readings istaken across eachset of windings ateach 15of rotation


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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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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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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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Battery testingUsing a digital hydrometer, records specific gravity and temperature.


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Battery testingUsing an impedance tester, also records voltage,


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Battery testingResults of a routine test, showing, voltage, impedance and specific gravityfor each cell of a 110V battery bank.


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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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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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Ultrasonics

Listening to a 6.6kV circuit breaker.


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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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Vibration and lube oil analysis

Vibration sensor pad

Oil sample point


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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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