INVESTIGATING THE MALFUNCTION OF A HYDRO- GENERATOR'S COOLING-SYSTEM
Electro-magnetic losses within a hydro-generator are sources of heat which heat the generator, and then have to be conducted away. This may, however, cause a temperature rise of the stator bars thus reducing the life-span of the insulation materials. Therefore, any temperature rise of the stator windings is limited. In order to inspect the operation of a cooling-system, several temperature sensors have to be integrated into the stator core in order to measure its temperature, which should not exceed 80 0 C. Temperature measurements performed on a generator showed some deviations from the design temperatures, especially at full-power operation. Thus, an attempt was made to analyse the operation of a cooling-system, and to eventually increase its cooling capacity. It was impossible to perform any complex measurements during the generator’s operation, due to safety reasons. Therefore, our work was limited to 3D CFD simulations using ANSYS CFX 11 solver. The simulations were partly supported by the measurements of some main integral parameters, such as mass-flow rate and pressure drop across the cooling ducts and radiators, as performed during generator idling. The results are presented and discussed in this paper.
Investigation on the performance of a 277.8 MVA synchronous air-cooled hydrogenerator through loss models
Synchronous generators (SGs) are widely used in power generating plants including hydropower as it is easy to control, supports large amount of reactive power, and offers higher energy efficiency in comparison with asynchronous generators. SGs are often overloaded through hydro-turbines by utilizing excess water flow in the river (e.g. 1000 MW Kancham Wangtoo hydropower station (India) at 20% continuous overloading condition for more than six weeks). This paper investigates the efficiency of a 277.8 MVA SG, through its loss models, under two operating conditions: (i) at rated load, (ii) at 20% overload. Temperature of cooling air inlet to the stator of SG (primary cooling) and the temperature of water inlet to the cooler (secondary cooling) are considered for the analysis. Simulated results are compared with a commissioned generator through the on-site measurements. From the test results, it is observed that the cooler performance (temperature of air leaving from the cooler) was poor at overloads which causes reduction in efficiency and temperature-rise in stator windings of tested SG.
The MR-TOF-MS isobar separator for the TITAN facility at TRIUMF
At TRIUMF’s Ion Trap for Atomic and Nuclear Science (TITAN) a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) will extend TITAN’s capabilities and facilitate mass measurements and in-trap decay spectroscopy of exotic nuclei that so far have not been possible due to strong isobaric contamination. This MR-TOF-MS will also enable mass measurements of very short-lived nuclides (half-life > 1 ms) that are produced in very low quantities (a few detected ions overall). In order to allow the installation of an MR-TOF-MS in the restricted space on the platform, on which the TITAN facility is located, novel mass spectrometric methods have been developed. Transport, cooling and distribution of the ions inside the device is done using a buffer gas-filled RFQ-based ion beam switchyard. Mass selection is achieved using a dynamic retrapping technique after time-of-flight analysis in an electrostatic isochronous reflector system. Only due to the combination of these novel methods the realization of an MR-TOF-MS based isobar separator at TITAN has become possible. The device has been built, commissioned off-line and is currently under installation at TITAN.