Supply disruptions can significantly negatively impact specific customers, particularly within industries where such interruptions can result in substantial costs. The productivity and competitiveness of both manufacturing and service sectors increasingly rely on the quality of electricity supply, which is, in turn, influenced by the efficiency of continuity indicators. Portugal began monitoring these continuity indicators in 2001 and subsequently implemented a continuity of supply incentive regime in 2003. Consequently, there has been a consistent improvement in these indi-cators, driving ongoing improvements in service quality and customer satisfaction. Recently, an analysis was conducted to evaluate the quality of service in mainland Portugal from 2014 to 2022, focusing on the frequency and duration of continuity service indicators. The study applied a two-way analysis of variance (ANOVA) to investigate potential differences between two factors: Quality Service Regulation (QSR) zone and municipality codes. The findings highlighted the need of a more precise analysis of the variables representing continuity indicators. Building on this previous work, the authors transformed the mentioned variables to ensure their valid-ity during residual analysis, resulting in satisfactory outcomes that were subsequently discussed.

The first author, this work was partially supported by Fundação para a Ciência e a Tecnologia, I.P. (FCT) [ISTAR Projects: UIDB/04466/2020 and UIDP/04466/2020].

Electricity continuity service,Interruption frequency index,Interruption duration index,Two–way ANOVA

• Mathematics - Natural Sciences