Abstract:In this paper, we analysed the growing penetration of generating units from renewable energy sources in transmission power systems. Among the possible effects of the interaction of distributed generation (DG) with transmission systems, we considered the abnormal operating conditions caused by short circuits in the transmission systems and the resulting voltage sags that occur in the network. A systematic method is presented for analysing the voltage sag behaviour of any transmission system in which large DG units are connected to the transmission system by means of High Voltage/Medium Voltage (HV/MV) stations. The method proposed for obtaining the voltage sags is the fault position method (FPM), from which we derived a graphical visualization of the during-fault voltage (DFV) matrix as a valuable tool to obtain an immediate measure of the propagation of voltage sags in the network. The results obtained were based on a portion of a real transmission system. The system that we considered is an actual portion of the Italian transmission system, and all of the quantities we used were obtained from the data of the Transmission system operator (TSO).

In this paper, we dealt with the problem of the voltage sags due to faults along the lines using the Fault Position Method (FPM). The objective of the study was to demonstrate that for actual transmission systems the FPM can be used in a very effective way to solve real problems with acceptable accuracy and reduced computational times. A very simple procedure for adding further fault positions along the lines, if needed, is proposed. Numerical applications provide evidence of the proposed method. The results obtained were based on a portion of the Italian transmission system and the quantities we used were obtained from the data of the TSO.

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