The cost of electricity for the reverse osmosis desalination process is up to 50% of the cost per cubic meter of water produce. Currently, the reduction of energy consumption is the main objective of the research on reverse osmosis plants. This document presents a power system analysis of the seawater desalination plant in Algeria with different load scenarios with a power of 50 MW made available by the electricity company Sonelgaz and a distribution level of 220/11/0.69/0.4 kV and a 2 MW diesel generator at the 0.4 kV level. The objective of this study is to analyze and dimension a general distribution network of an industrial customer through the power flow with different load and contingency scenarios (full load, full load N-1, low load, emergency system) to know and control its optimal and flexible operation. In a second step, the dimensioning of different protective devices is planned through a short circuit analysis of this network in order to evaluate the performance of the system. The ETAP program is used to carry out our simulation of this industrial plant and the effectiveness of the results is proven by comparisons with real measurements for the power flow analysis on the one hand and on the other hand with the results obtained by the builder for the short circuit analysis.