Actions to Handle Increasing Distributed Generation and Rising Voltage during Low-Demand Periods: Tap Staggering Practices and Field Tests in the Italian Transmission Network

This paper deals with the voltage regulation strategies implemented in the Italian transmission network to face the increasing problem of high voltages during time periods characterized by low demand. After an introduction in which this very actual problem is discussed, the focus is on tap staggering practices. Although tap staggering is not a new idea, it is gaining practical importance only in the very last few years as a means of enhancing the inductive power drawn from the grid and, therefore, limiting the voltage rise. Accordingly, tap staggering contributes to the mitigation of the problems caused by the increasing penetration of renewable energy sources and thus can allow an increase in the share of renewable energy sources. The paper presents the different tap staggering practices that are being defined by the Italian transmission system operator and reports some tap staggering tests recently performed on large autotransformers as well as phase-shifter transformers.