TYPE TEST AND TORSIONAL VIBRATION MEASUREMENT OF A GIGATOP 4-POLE GENERATOR FOR AN EPR POWER PLANT

摘要

The GIGATOP 4-pole turbo generators are designed for all types of half-speed turbines fornuclear power plants (NPP).For an EPR reactor, the first 1800 MW class turbogenerator designed by Alstom (OEM) is theFlamanville 3 generator. This machine is a new model, which will be the base of furtherderived units for future 50 Hz EPR applications or equivalent.It has been delivered after comprehensive type tests in factory, which demonstrate andvalidates the performances of the generator and of its future evolutions.The Flamanville 3 generator apparent power output is set at 1944 MVA, which alreadyrepresents a substantial step compared to the world’s largest generators in operation in EDFnuclear fleet, the N4 units operating since the 1990s.This output has been achieved using proven technologies already used on other nuclear andfossil units.The running tests were performed for stator voltages and currents higher than the rated values,which constitute one of the worldwide largest powers ever running tested. The test stand ofthe OEM has been upgraded to enable an increase of the driving power by 40 %.The evaluation of the test results allows the overall performance of the machine to bechecked. First heat run tests confirm that the temperature rise of the different parts of thegenerator are in compliance with the IEC standard criteria and also conform to calculatedvalues.In addition to generator standard instrumentation, a large set of temporary test instrumentationwas installed in order to monitor temperatures, currents, vibrations, voltages, flux density, gasvelocities, etc. The temperature of neutral and short-circuit bars were monitored with athermal camera. Three heat run tests were performed:1. Un-excited2. Stator winding in open-circuit and field winding excited to obtain 110 % of ratedarmature voltage.3. Stator winding short-circuited and field winding excited to obtain 105 % of ratedarmature current.The measured temperatures of stator core, flux shields, stator and rotor windings wererecorded and checked during the tests.These heat run tests were also used to measure and validate the predicted efficiency, bymeasuring the power absorbed by the calibrated driving motors of the test stand. A torquemeter method was also tested during these tests.In addition to the heat run tests the short-circuit ratio Kc was determined.Dynamic characteristics were evaluated as well. Sudden short-circuit tests were performed inorder to validate the calculated reactances and time constants.From a mechanical point of view, special attention was paid to rotor torsional behaviour. Thetorsional natural frequencies and responses to sudden and permanent short circuits werecalculated as input to validate the shaft line integrity.During the spin pit testing of the generator rotor the torsional oscillations were measuredusing a telemetry system.The evaluation provides the torsional natural frequencies during balancing runs in the spin pit.In addition two modal analyses were performed in order to assess the influence of the drivingshaft line of the running test configuration.During the rotating type tests (electrical short-circuit tests) the torsional natural frequenciesand time responses due to short circuit were measured. The vibration responses are transientones for the sudden short circuit, and are harmonic responses for the permanent two-phasesshort circuit. The post-processing delivers vibration time histories and spectral analysis.