Time-Series Based Cable Selection for a Medium Voltage Wind Energy Network

Abstract

This paper analyzes various factors that influence the cable selection for delivering wind energy to an electrical network. It also investigates when the thermal and voltage limit become the dominant limiting factor in order to obtain the correct economical loading range (ELR) and load reach of a cable. In addition, the influence of power factor setting and capacity factor of wind turbines on cable sizing are also presented. To account for the stochastic behavior of wind power and electricity price, time series measurements are employed to evaluate the cost of energy losses in a cable. Procedures are summarized to illustrate the cable selection for a wind energy network. The illustration is performed on a 20 kV wind energy network in Sweden.The results indicate that electricity price, discount rate and wind turbine capacity factor affect the ELR of the cable significantly. On the other hand, when the number of evaluation year is reduced from 40 years to 20 years, the ELR does not vary significantly. Furthermore, in the case of no voltage violation, the cable length does not affect the ELR. Moreover, the power factor setting of wind turbines does not affect ELR, but has a significant influence on the load reach of a cable. For the case network with 28 MW wind installation, 8% savings are obtained when using the selected economical cables instead of the thinnest cables; 2% savings are obtained when using the optimal power factor instead of the unity power factor. The cable selection method proposed in this paper can be used by both wind farm designers and network operators to select cables for their wind energy collection grids.