Review of Distribution Network Phase Unbalance: Scale, Causes, Consequences, Solutions, and Future Research Direction

Abstract

Phase unbalance is widespread in the distribution networks in the UK, continental Europe, US, China, and other countries. First, this paper reviews the mass scale of phase unbalance and its causes and consequences. Three challenges arise from phase rebalancing: the scalability, data scarcity, and adaptability (towards changing unbalance over time) challenges. Solutions to address the challenges are: 1) using retrofit-able, maintenance-free, automatic solutions to overcome the scalability challenge; 2) using data analytics to overcome the data-scarcity challenge; and 3) using phase balancers or other online phase rebalancing solutions to overcome the adaptability challenge. This paper categorizes existing phase rebalancing solutions into three classes: 1) load/lateral re-phasing; 2) using phase balancers; 3) controlling energy storage, electric vehicles, distributed generation, and micro-grids for phase rebalancing. Their advantages and limitations are analyzed and ways to overcome the limitations are recommended. Finally, this paper suggests future research topics: 1) long-term forecast of phase unbalance; 2) whole-system analysis of the unbalance-induced costs; 3) phase unbalance diagnosis for data-scarce LV networks; 4) techno-commercial solutions to exploit the flexibility from large three-phase customers for phase balancing; 5) the optimal placement of phase balancers; 6) the transition from single-phase customers to three-phase customers. <br>

Optimal Allocation of Battery Energy Storage Systems to Enhance System Performance and Reliability in Unbalanced Distribution Networks

“…V max and V min for mth bus are calculated by applying the ±6% voltage violation limits. The voltage deviation index is formulated as a percentage ( %VDI), as shown in (42) [14].…”

“…In the real world, system voltage is rarely balanced, mainly due to the unbalanced loading in the distribution system [41]. For instance, phase imbalance frequently occurs in US distribution systems, particularly the medium voltage level grid [42]. Severe voltage unbalance would magnify the system losses and shrink the capacity of the electrical components in the network [43].…”

Evaluation of lightning‐induced overvoltage on a 10 kV distribution line based on electromagnetic return‐stroke model using finite‐difference time‐domain

“…Lightning is an atmospheric discharge process involving the temporary neutralisation of two electrically charged regions, resulting in the instantaneous release of a gigajoule of energy [1][2][3]. When lightning strikes the ground in the vicinity of the distribution line, electromagnetic signals may induce overvoltage on the line, causing unbalanced faults or trip accidents [4]. Studies have shown that 90% of power interruptions on distribution lines are caused by lightning-induced overvoltage, affecting many regions worldwide including in China and Iran [3].…”

A Novel Refined Regulation Method with Modified Genetic Commutation Algorithm to Reduce Three-Phase Imbalanced Ratio in Low-Voltage Distribution Networks

“…However, with the increase in power demand and variations in power load, the issue of three-phase imbalance in LVDNs is becoming increasingly prominent [1]. Uneven current distribution in the power grid, due to a three-phase imbalance, can cause equipment overload, damage, and low energy efficiency, all of which have a major negative impact on the dependability and quality of the power supply [2][3][4]. Therefore, it is of great theoretical and practical significance to solve the three-phase load imbalance problem in low-voltage distribution networks.…”