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Go to Editorial ManagerTime series analysis for hydrological phenomena has an important role in water resources engineering. In this study, seven models of ARIMA family are tested for forecasting the monthly discharge at Hit station on Euphrates river in Iraq. The statistical analyses were done for models with help of IBM SPSS statistics 21 software, The number of observations used is equal to 480 reading, start from October 1932 and end at September 1972, this period represents the near-natural stream flow of the river before the construction of dams in Syria and Turkey. Statistical tests such as T-test and F-test were used to detect any change in Mean and Variance at 95% significant probability level. Results showed that the best model is (2,0,1)×(0,1,1) 12 which gives minimum error and good agreement between observed and forecast discharge.
Low-voltage (LV) residential distribution networks are highly susceptible to voltage unbalance due to the stochastic and time-varying nature of residential single-phase loads. The assessment methodologies based on snapshots have a difficulty in allowing the spatial and temporal characteristics of the unbalance events. Based on 10-minute resolution time-series unbalanced power flow simulation in OpenDSS, this paper introduces a time-dependent evaluation framework. While the time-varying load profiles and Monte Carlo analysis represent the variance in daily load and uncertainty in phase allocation, respectively. The parameters include both voltage unbalance assessment indexes (i.e., Voltage Unbalance Factor (VUF), Phase Voltage Unbalance Rate (PVUR)), as well as temporal risk indicators (i.e., Time-at-Risk (TAR) and a TimeDependent Unbalance Risk Index (TD-URI)). The analysis produced shows voltage unbalance behaves transitory and locational, being most threatening during peak demand and faraway buses. The quantity and duration of unbalance events are reduced significantly with the help of phase balancing. The framework has been reconciled with the EN 50160 and it aims to buttress a tangible foundation for planning-oriented voltage unbalance evaluation and remediation in low-voltage residential networks.