1. Condition Monitoring of Generators
ELEC-E8401 Condition Monitoring of Electrical Equipment
Minna Luojus
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2. Introduction Generator – one of the prime devices in a power plant
Fixing of a generator takes a long time
The cost of lost production significant
On-line continuous measurements
Measurements and inspections during revisions
On-line partial discharge (PD) monitoring system
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3. On-line Continuous Measurements 1/2
Vibration Measurements
Several vibration measurement sensors installed
Axial and Radial x/y
Automatic controlling system
Permitted vibration level exceeded → alarm
Vibration too high → shut down command
Temperature Measurements
Temperature measurement sensors
Temperature of generator windings is followed
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4. On-line Continuous Measurements 2/2
Protection Relays
For generator and its electrical system
In total approx. 30 different relays
Generator over current, over voltage, reverse power, over frequency etc.
Measurement of Shaft Movement
Generator and turbine equipped with shaft movement measurement system
Shaft movement affects on bearings function
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5. Condition Monitoring 1/3
Measuring of Isolation Resistance
The isolation resistance of generator windings measured
At least once a year – usually during revision or long shut down
Mechanical inspections
During generator revision, depending on the running hours of generator
Breaking and cracs of different mechanical constructions
Retaining rings, after running hours (if old material used)
Stator windings slots and end-windings, after running hours
Tan Delta Monitoring System
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6. Condition Monitoring 2/3 - On-line Partial Discharge (PD) Monitoring System
Continuous acquisition and analysis of electrical discharges on an object interacted by voltage
Early recognition of discharge phenomena
Sensitively detects and analyses location and cause of PD
Main components of the PD monitoring system:
Couplers
PD signal processor
Data acquisition and analyzing system
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7. Condition Monitoring 3/3 - On-line Partial Discharge (PD) Monitoring System
Signals originating in the insulation system decoupled by the couplers
Three dimensions used in the processing result:
Phase angle  (deg)
Number of pulses n
Apparent charge q (nC)
Figures: Siemens, Partial Discharge Measurement Flyer,
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8. Conclusion Generator one of the main components in a power plant
→ Condition monitoring important!
Normal on-line measuring system
On-line continuous measurements
Condition monitoring system
Inspections and measurements during revision
On-line partial discharge (PD) monitoring system
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