General Planning Principles of High Voltage Distribution Networks Including Wind Power
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In Finland, the high voltage distribution networks (HVDNs) include all 110 kV lines which are not part of the transmission network of the Finnish electricity transmission system operator, Fingrid. Currently, the role of the HVDNs in the business operations of the network companies is generally relatively small. This is because the amount of network renovations to the networks and the construction needs for new HVDNs are small. However, this will probably change in the future, since the planning needs of the HVDNs will increase with the increasing amount of wind power in the networks. In addition, the effects of wind power on the HVDNs are relatively unknown, since the majority of the wind power research focuses on the effects of wind power on the whole power network or on the effects of small wind plants on 20 kV or low-voltage networks. This thesis is a part of a Finnish national 5-year research program called Smart Grid and Energy Market (SGEM). The main purpose of this thesis is to describe the general planning principles of the HVDNs and to analyze the effects of large-scale wind power production on the different types of HVDNs in Finland. Moreover, the thesis aims to examine what kind of impacts the wind power plants in the HVDNs have on the planning and operation of the networks. In addition, the thesis will study the advantages and disadvantages of demand side management (DSM) in the planning and operation of the HVDNs with wind power. The thesis consists of making a literature survey about the subject, which is supported by general level network simulations with a HVDN test system with two wind farms and by interviews with some network operator personnel. The simulations of the thesis examine the wind power capacity of the different types of HVDNs, the variability of the load and wind power production in relation to each other, the voltage variations and power losses in the HVDNs with wind power and, finally, the effects of DSM on the wind power capacity, voltages and power losses of the networks. Actual measured data is being used in the simulations in the modelling of the fluctuations of the wind power production and network loads. In the end, the conclusions about the wind power effects on the HVDN planning and operation are made based on the literature survey, interviews and simulations.