An investigation on the effects of feeder outages and non-linear loads on 11kV ring distribution network efficiency.
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This study investigates the impact of power quality problems on the efficiency of a ring distribution network. The paper focuses on the effects of outage and harmonics on the distribution network efficiency and the practical implications on power system economics and reliability. An 11 kV ring distribution network was modeled and simulated in DigSilent PowerFactory (Demo version) 14.0.512 software package. Five case studies were conducted on the network for normal operation conditions and abnormal conditions (outage and harmonics). A methodology to estimate the technical losses (economic losses) in the distribution system was developed and used as a basis for determining the network efficiency. A load flow based analysis was carried out on the distribution system to determine the voltage and current profiles under normal and abnormal conditions. It emerged that the loss of feeder cables or lines in the network has an adverse impact on the efficiency of the network. This raises the question on the existence and the need of an optimum supply configuration. It also puts an increased focus on the need of improved reliability engineering in distribution systems as the costs of failures could be high. The authors conclude that the efficiency of a ring distribution network is affected adversely during contingency (outage and harmonics). The degree to which the efficiency is affected depends on the initial optimal design configuration and the nature of the disturbance or contingency condition. Preventative steps that can be taken to “harden” equipment and systems to PQ problems are also suggested.