## 1 Introduction  
Electricity loss refers to the amount of energy that is dissipated or wasted during the process of generation, transmission, and distribution. This loss is obtained from the difference between the energy generated and the energy billed to the end consumer [1; 2]. Electricity losses are divided into two groups: technical losses (TLs), or natural losses of the system, and non-technical losses (NTLs) [3]. TLs are inevitable and are related to the processes of energy transformation and transportation through the electrical system. These can be reduced through technological advancements and proper maintenance of electrical networks [1; 3]. NTLs occur due to administrative errors that arise in the management of electricity marketing (such as un-billed electricity), the malfunctioning of measuring equipment, and primarily, fraud and electricity theft. These losses are highly prevalent in the distribution stage [4]. The distribution of non-technical losses (NTLs) can vary depending on the distribution company, region, or country. From the analysis of the inspectors' comments in the provided data, it was identified that approximately 15% of these losses are due to administrative errors, such as billing failures, measurement errors, omissions in meter readings, and incorrect account records. In contrast, 85% of them are attributed to electricity fraud and theft, including tampering with meters, illegal connections, and deliberate fraud by consumers. In [2], it is established that losses due to bill collection, overstaffing, and under-pricing can vary between 19% and 70% of the total losses. Energy fraud occurs through the tampering of electricity meters, which causes measurement errors and consequently changes in energy billing. Energy theft is manifested in clandestine connections and direct connections from the grid, without any billing [1; 5]. Theft and fraud are serious problems for utility companies in both developing and developed countries, causing significant economic harm to electricity companies [6; 7]. In Montevideo, the capital city of Uruguay, NTLs account for approximately 13% of the total energy distributed [8]. In Iran, NTLs caused by electricity theft represent more than 15% of the generation capacity [9]. [PERSON] et al. indicate that for the United States and the United Kingdom, the financial losses caused by electricity theft range between 1 billion and 6 billion each year [10]. [PERSON] et al. established that in the Russian Federation, NTLs, in terms of the volume supplied to the distribution network, vary from 0.06% to over 25%, depending on the region and the organization of the electrical network [11]. In South Africa, it is estimated that there were irrecoverable losses of ZAR 685 million in 2020 [12]. Figure 1 shows the reported percentages of electricity losses in Ecuador (a developing country located in South America) from 2007 to 2023. A decrease in the percentage of losses is observed from 21.42% reported in 2007 to 15.02% in 2023. However, an increase is noted since 2018 with a tendency towards higher levels. As observed, the problem has persisted over time, with a notable increase in NTLs from 3.9% recorded in 2015 to 8.63% in 2023. Figure 1: Percentage of electrical losses in Ecuador, period 2007–2023. Source: ARCERNNR, 2023 [13]. In the Ecuadorian case, it is possible to estimate the economic impact caused by NTLs. Figure 2 presents the result of this estimation based on the energy billed by electric distribution companies. It indicates that in 2023, NTLs represented USD 242.84 million for the Ecuadorian state, and this value may increase in the future. Despite significant efforts and substantial investments by the country's electric utilities, non-technical losses (NTLs) remain a persistent challenge. Addressing this issue requires the implementation of advanced analytical techniques and efficient methodologies to better control and mitigate these losses. This study proposes a data-driven methodology for detecting NTLs in electric distribution systems.