Power uprates pose a threat to electrical generators due to possible parasite effects that can develop potential failure sources with catastrophic consequences in most cases. In that sense, it is important to pay clos...Power uprates pose a threat to electrical generators due to possible parasite effects that can develop potential failure sources with catastrophic consequences in most cases. In that sense, it is important to pay close attention to overheating, which results from excessive system losses and cooling system inefficiency. The end region of a stator is the most sensitive part to overheating. The calculation of magnetic fields, the evaluation of eddy-current losses and the determination of loss-derived temperature increases, are challenging problems requiring the use of simulation methods. The most usual methodology is the finite element method, or linear regression. In order to address this methodology, a calculation method was developed to determine temperature increases in the last stator package. The mathematical model developed was based on an artificial intelligence technique, more specifically neural networks. The model was successfully applied to estimate temperatures associated to 108% power and used to extrapolate temperature values for a power uprate to 113.48%. This last scenario was also useful to test extrapolation accuracy. The method is applied to determine core-end temperature when power is uprated to 117.78%. At that point, the temperature value will be compared to with the values obtained using finite elements method and multivariate regression.展开更多
Overall purpose of a power uprate and lifetime extension project （PLEX） is to modernize the power station cost-efficiently resulting in fulfilling the following overall requirements. The primary target is to meet th...Overall purpose of a power uprate and lifetime extension project （PLEX） is to modernize the power station cost-efficiently resulting in fulfilling the following overall requirements. The primary target is to meet the requirements provided by the local regulations from the regulatory offices. The controlling, monitoring and power supply of safety functions have to comply with these regulations. Any deviations from the existing safety analysis report （SAR） have to be corrected. On top of the safety measures the general technical status should be raised to extend the lifetime to 60 years. A high availability during the modernization has to be assured.展开更多
The voltage uprating of existing overhead lines is an interesting solution for increasing the transmission of electricity, especially in areas where it is difficult to build new lines. If a line is uprated with minor ...The voltage uprating of existing overhead lines is an interesting solution for increasing the transmission of electricity, especially in areas where it is difficult to build new lines. If a line is uprated with minor changes of its design and without improvement of the grounding electrodes of towers, its lightning performance remains unchanged. The consequence is that the uprated line will have a lightning flashover rate very high compared to an overhead line of same nominal voltage but of standard design. One attractive solution to solve this problem is to use line arresters. The goal of this paper is to study the use of line arresters to achieve a satisfactory lightning performance of an overhead line uprated from 225 kV to 400 kV without major design modifications. In order to compare different strategies of line arrester installation the flashover rate is calculated based on a software able to launch automatically EMTP-RV. The software named LIPS has been developed under the cover of a partnership between Hydro-Quebec, RTE and EDF.展开更多
文摘Power uprates pose a threat to electrical generators due to possible parasite effects that can develop potential failure sources with catastrophic consequences in most cases. In that sense, it is important to pay close attention to overheating, which results from excessive system losses and cooling system inefficiency. The end region of a stator is the most sensitive part to overheating. The calculation of magnetic fields, the evaluation of eddy-current losses and the determination of loss-derived temperature increases, are challenging problems requiring the use of simulation methods. The most usual methodology is the finite element method, or linear regression. In order to address this methodology, a calculation method was developed to determine temperature increases in the last stator package. The mathematical model developed was based on an artificial intelligence technique, more specifically neural networks. The model was successfully applied to estimate temperatures associated to 108% power and used to extrapolate temperature values for a power uprate to 113.48%. This last scenario was also useful to test extrapolation accuracy. The method is applied to determine core-end temperature when power is uprated to 117.78%. At that point, the temperature value will be compared to with the values obtained using finite elements method and multivariate regression.
文摘Overall purpose of a power uprate and lifetime extension project （PLEX） is to modernize the power station cost-efficiently resulting in fulfilling the following overall requirements. The primary target is to meet the requirements provided by the local regulations from the regulatory offices. The controlling, monitoring and power supply of safety functions have to comply with these regulations. Any deviations from the existing safety analysis report （SAR） have to be corrected. On top of the safety measures the general technical status should be raised to extend the lifetime to 60 years. A high availability during the modernization has to be assured.
文摘The voltage uprating of existing overhead lines is an interesting solution for increasing the transmission of electricity, especially in areas where it is difficult to build new lines. If a line is uprated with minor changes of its design and without improvement of the grounding electrodes of towers, its lightning performance remains unchanged. The consequence is that the uprated line will have a lightning flashover rate very high compared to an overhead line of same nominal voltage but of standard design. One attractive solution to solve this problem is to use line arresters. The goal of this paper is to study the use of line arresters to achieve a satisfactory lightning performance of an overhead line uprated from 225 kV to 400 kV without major design modifications. In order to compare different strategies of line arrester installation the flashover rate is calculated based on a software able to launch automatically EMTP-RV. The software named LIPS has been developed under the cover of a partnership between Hydro-Quebec, RTE and EDF.
