The energizing of large power transformers has long been considered a critical event in the operation of an electric power system. When a transformer is energized by the utility, a typical inrush current could be as h...The energizing of large power transformers has long been considered a critical event in the operation of an electric power system. When a transformer is energized by the utility, a typical inrush current could be as high as ten times its rated current. This could cause many problems from mechanical stress on transformer windings to harmonics injection, and system protection malfunction. There have been numerous researches focusing on calculation and mitigation of the transformer inrush current. With the development of smart grid, distributed generation from independent power producers (IPPs) is growing rapidly. This paper investigates the inrush current due to black start of an IPP system with several parallel transformers, through a simulation model in DIgSILENT Power Factory software. The study demonstrates that a single genset is capable of energizing a group of transformers since the overall inrush current is slightly above the inrush of the transformer directly connected to the generator. In addition, a simple method is proposed to mitigate the inrush current of the transformers using an auxiliary transformer.展开更多
Decentralised energy (DE), also known as distributed energy, refers to power generation and energy storage systems located at or near the point of use;and may also be connected to a local distribution network system o...Decentralised energy (DE), also known as distributed energy, refers to power generation and energy storage systems located at or near the point of use;and may also be connected to a local distribution network system or to a high voltage transmission system either directly or through a local distribution network system. It is generated or stored by a variety of small devices commonly referred to as distributed energy resources (DER);the definition also extends to include stand-alone systems completely isolated from the public networks. The contribution made by independent power producers (IPP’s) through deployment of DER in the African energy market is critical to fast-tracking the deployment of renewables, diversification of the energy mix and enhancing access to modern and clean energy. There is need to develop policy mechanisms aimed at enhancing the current positive drive in the energy market;and this has been observed to be a driving factor in countries which have developed appropriate policy strategies. This paper presents the concept of DE in detail and how it could complement efforts to addressing the current energy crises in Southern Africa;it also looks at policy developments in Africa and presents the scenarios in the two southern African countries of South Africa and Botswana. The research is based on an extensive review of literature on the subject matter, consultations with stakeholders as well as feedback from the Learning Network for Sustainable Energy Systems (LeNSes) workshops.展开更多
文摘The energizing of large power transformers has long been considered a critical event in the operation of an electric power system. When a transformer is energized by the utility, a typical inrush current could be as high as ten times its rated current. This could cause many problems from mechanical stress on transformer windings to harmonics injection, and system protection malfunction. There have been numerous researches focusing on calculation and mitigation of the transformer inrush current. With the development of smart grid, distributed generation from independent power producers (IPPs) is growing rapidly. This paper investigates the inrush current due to black start of an IPP system with several parallel transformers, through a simulation model in DIgSILENT Power Factory software. The study demonstrates that a single genset is capable of energizing a group of transformers since the overall inrush current is slightly above the inrush of the transformer directly connected to the generator. In addition, a simple method is proposed to mitigate the inrush current of the transformers using an auxiliary transformer.
文摘Decentralised energy (DE), also known as distributed energy, refers to power generation and energy storage systems located at or near the point of use;and may also be connected to a local distribution network system or to a high voltage transmission system either directly or through a local distribution network system. It is generated or stored by a variety of small devices commonly referred to as distributed energy resources (DER);the definition also extends to include stand-alone systems completely isolated from the public networks. The contribution made by independent power producers (IPP’s) through deployment of DER in the African energy market is critical to fast-tracking the deployment of renewables, diversification of the energy mix and enhancing access to modern and clean energy. There is need to develop policy mechanisms aimed at enhancing the current positive drive in the energy market;and this has been observed to be a driving factor in countries which have developed appropriate policy strategies. This paper presents the concept of DE in detail and how it could complement efforts to addressing the current energy crises in Southern Africa;it also looks at policy developments in Africa and presents the scenarios in the two southern African countries of South Africa and Botswana. The research is based on an extensive review of literature on the subject matter, consultations with stakeholders as well as feedback from the Learning Network for Sustainable Energy Systems (LeNSes) workshops.
