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In distribution power systems line transposition is not a common practice and phase loading levels are always changing. Therefore, perfect balance is never achieved at a distribution level. Non-transposed lines can cause unequal voltage drops between phases and this may be further exacerbated by uneven loads in each phase. Consequently, the voltage magnitude of a certain phase may suffer a severe decrease, breaching the lower voltage limit or unbalanced three-phase voltages at a remote bus may violate the percentage voltage imbalance accepted in the standards. This paper examines the mechanism of causing uneven voltage drops and investigates the impacts of unbalanced line configurations with different phase loading levels on network voltage imbalance. Methodologies are proposed to analyze voltage drops affected by line and load imbalance. Based on these methods, general guidelines are recommended to mitigate the voltage problems, which are useful for network analysis, planning and reconfiguration. [ABSTRACT FROM PUBLISHER]

With the rapid development of photovoltaic (PV) technology, more utility-scale PV systems are being integrated into rural areas where abundant and low-cost land is available. In these areas, step-voltage regulators (SVRs) with an open-delta configuration are widely used for voltage regulation. However, since SVRs were initially designed for tackling slow and smooth load variations, frequent PV output fluctuations can cause excessive tap changes. Moreover, rural communication facilities are normally expensive and underdeveloped, so only limited parameters are recorded with low resolution and reliability. Thus, much needed tap information cannot be properly monitored in a cost-effective way. In contrast, a downstream load center or utility-scale PV site is commonly well equipped with modern sensors and data acquisition systems, which provide the possibility for tap evaluation. Therefore, this paper proposes a new remote tap position estimation approach to accurately assess the upstream tap positions of open-delta SVRs from downstream measurements. Furthermore, the proposed approach is firmly validated through field testing under the support of the local utility and PV plant owner. This novel method not only enables reliable tap position monitoring with high precision for utilities to research PV–SVR interaction, but also provides valuable information to PV owners for correctly analyzing downstream voltage performance. [ABSTRACT FROM AUTHOR]