OLTC selection and switching reduction in multiple-feeder LV distribution networks

On-Load Tap Changers (OLTCs) are increasingly being considered to control the voltage in Low-Voltage (LV) distribution grids. Today, most OLTC control strategies are based on secondary transformer measurements, while a Field Measurement Based (FMB) control could increase the quality further. In this paper, field measurements, performed by a Distribution System Operator (DSO), are used to simulate the voltage quality improvement derived from implementing an OLTC with FMB control. Unfortunately, FMB control results in an unacceptable number of tap changes, so, in order to improve FMB control, two strategies to reduce the number of tap changes are presented. Next, an OLTC selection procedure is clarified. Both the voltage range of the OLTC and the tap position occurrence show that several OLTCs are not suited to increase the voltage quality. A voltage quality analysis shows that a well-selected OLTC with FMB control result in a significant increase in voltage quality, which allows more Distributed Energy Resources (DERs) to be connected in the existing LV distribution grid.