Condition Monitoring of Generators ELEC-E8401 Condition Monitoring of Electrical Equipment Minna Luojus 25.4.2016 1/8

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 25.4.2016 2/8

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 25.4.2016 3/8

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 25.4.2016 4/8

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 70 000 running hours (if old material used) Stator windings slots and end-windings, after 50 000 running hours Tan Delta Monitoring System 25.4.2016 5/8

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 25.4.2016 6/8

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, http://www.energy.siemens.com/br/pool/hq/services/industrial-applications/generators/EN-Generator-Partial-Discharge-Measurement-Flyer.pdf 25.4.2016 7/8

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 25.4.2016 8/8