Single-phase voltage regulators and three-phase systems

Voltage regulators are applied on distribution systems to control the voltage delivered to customers within acceptable industry standards. Concerns about the quality of electric power delivered to customers by electric utility companies have raised the level of awareness of high- and low-voltage conditions at customer facilities. Normally occurring voltage drops through lines and transformers vary with the load level on the system. Voltage regulators, when properly applied, can compensate for these voltage drops and keep customer voltage within proper limits. Single-phase voltage regulators can be applied on three-phase systems in a variety of ways, including grounded-wye, open-wye, closed-delta, and open-delta. The capabilities of the regulator systems are affected by the system design. In this article, the authors review the characteristics of the closed-delta and wye applications, and discuss the advantages and disadvantages of each application scheme. The impact of the regulator connection on overcurrent protection is also reviewed.