Investigation of voltage unbalance in low voltage electric power distribution network under steady state mode

Abstract

With the ever increasing use of semiconductor devices and information technology (ICT) equipment in the industry's, homes and offices voltage quality are gaining meaningful attention to both industry and the electric utility. Poor voltage quality cause unusually large economic losses all over the world, since voltage quality problem is one of the major power quality disturbances. This report provides an investigative study on the typical 11/0.4 kV, low voltage electric power distribution network. The network was modelled with standard network parameters for low voltage typical electric power distribution network using MATLAB/Simulink Sim Power System tool box. Results obtained from simulation with distribution feeder length 0.5 km for unbalanced 3-phase loads are within the acceptable nominal voltage tolerance range of ± 5 % of the nominal voltage value at the customer's terminal. While this is admissible for customers close to the infeed terminal, it was established that an inadmissible poor voltage reaches the customers at the end of the distribution network for network lengths 0.8 km to 5 km. Voltages measured here were less than the standard allowable limit of 0.95 p.u, of nominal voltage value. The summary of the paper gives recommendations on effective methods for enhancing voltage profile and correcting the unbalanced voltage to an allowable standard.