In order to satisfy the needs of electricity use, but also to safeguard the reliability of the existing National Electricity Distribution Network, HEDNO must build new electricity distribution infrastructures as well as modernise existing electricity distribution infrastructures. In this context, HEDNO opted for the construction of a new K/D 150/20 kV in the Prefecture of Attica, which will be called Ilion K/D. The new K/D will be installed on a PPC property, where the open-air substation P/S 22/6,6 kV N. Liosion, is to be dismantled. In addition, two 150 kV underground cable lines will be implemented, with which the new Ilion C/C will be interconnected with the Acharnon hotspot.The basic feasibility and destination of the new Ilion K/R is to ensure the adequacy and increase the reliability of the electricity supply of all kinds of consumers (domestic, commercial, industrial etc.) in the region of Western Attica. With the construction and operation of the new Ilion K/W will discharge the K/D 150/20 kV of the wider area around Ilion, which have experienced high charges in recent years. Measurements of recent years show strong saturation of the HT and MT network and the existing HT/MT substations in the area and necessitate the timely integration of the new substation. Delay in construction poses a risk of incapacitating reliable supply of existing and new loads in the area, if there is a failure in the existing facilities of the Network.With the installation of the new Ilion K/R, within the geographical area of the cargoes served, a significant reduction in the length of the MT lines and their uniform geographical dispersion will be achieved. In this way, the following are achieved: the electricity losses are significantly reduced proportionally the probability of error or failure along the lines improves the quality of power provided to consumers reduces the frequency and the duration of power interruptions enhances the stabilisation of voltage.These factors have gained particular importance in recent years, due to the demanding and sensitive, power quality, devices that are now used extensively in both homes and businesses. The installation of a P/S within the geographical area of the serviced charges significantly reduces electricity losses, which are converted into heat along the lines due to their omic resistance. This is a factor with an essential environmental dimension and importance, given that increased electrical losses result in a waste of valuable primary energy resources, as well as a burden on the heating effects of the atmosphere. The quality of consumer supply is also related to the length of the network lines, as the probability of faults and faults on the lines as well as observed voltage disturbances vary accordingly.