The chronological limits of this work are defined by the publication of the Law of Electrification of the Country, in December 1944 and by the establishment of the company EDP - Electricidade de Portugal, in June 1976, after the nationalization of the electricity sector, in the previous year. That legal statute defined the basis of electrification in almost all aspects, the definition of the national electrical network concept; the rules for transportation and large energy distribution; rules for the concessions' operations the establishment of production centrals, lines of transportation and large and small distribution; the definition of the various price systems and subsystems, and the conditions according to which private initiatives might relate to the public networks of energy distribution. In the definition of the concept of national electrical network was implied a new understanding of what the State role should be in the sector; until then its action was confined to the production of legislation and supervision of various production systems and the establishment of networks; with this legal statute the State will establish the conditions to an increased involvement, assuming, in the future, the leadership of the energy production and distribution. To assume this role, the State will establish partnerships with the major electric companies in the country, invest on the constitution of power companies with mixed capital, for the construction of large hydroelectric and thermo producers that profited from national resources and for the establishment of a national transportation system, connecting the production and consumption centers. The State involvement, divided by shareholdings in five companies, which were the largest companies in the sector, originated an extraordinary increase of all important indicators in the sector until the mid-1970s, while areas linked to its development established conditions for national and international assertion. On this point, it is worth mentioning the engineers, who projected and executed major projects, the companies which provided materials, an area in which they will also position themselves as significant producers and suppliers, and major construction companies in the country that will assert themselves, in Portugal and abroad, largely by the experience gained in these business ventures. In the late 1960s, the State will take another step the definition of a model able to carry out the implementation of the electrification of the country, sponsoring the merger of all companies in the sector in which the State was a shareholder and creating, instead of those, a new one - the Companhia Portuguesa de Electricidade (CPE); through it the State had now a direct control over the largest production centers in the country, along with the transport network, now integrated into a single entity. Other ways in which the State action was decisive was the massive investment made in this sector, within the framework of the development plans (Planos de Fomento), both directly and through agencies and entities over which it had authority, specifically the social security institutions, the Banco de Fomento Nacional and the Caixa Geral de Depósitos, and even the reimbursements (comparticipações) an instrument through which the State supported the initiatives of small distribution. Moreover, the State was stipulating "decreasing scale tariffs", imposing a new tariff model to retailers who it supplied in high voltage, promoting gradual tariff harmonization. Around 1970, and as a consequence of these options, electricity production was concentrated in a company that represented more than 90% of the energy produced in Portugal at that time, besides being the owner of almost all the transport network for high voltage. At the same time a decrease in the number of dealers was observed through redemption, refusal of time extension of the concessions, or the concentration of these concessions in the Municipalities Federations (Federações de Municípios), with a particular focus on the northern and central interior of the country and in the south. At the same time the regional distribution to industrial customers and some concessions, were still in charge of larger companies and larger concession areas. But these companies depended entirely of the State policy for the sector, as the CPE, that supplied them, determined energy prices and tariff systems, allowing them a very circumscribed role, disguised through shareholdings in the CPE, which the State encouraged by giving them an apparent importance in the sector, which they no longer had. That appearance ended with the nationalization of the largest producers and distributors of electricity in the country, in April 1975 and the subsequent establishment of EDP - Electricidade de Portugal, in June 1976. This measure, along with another decision which determined that the entire national electricity sector - small dealers of production and distribution, Municipalities Federations, Municipal Services, and other agents with responsibilities in this sector -were gradually integrated into EDP, leaving only selfsupply systems appart; through EDP the State would control the entire strategic national electrical sector. If the planned integration of concessions operated by small businesses and the Municipalities Federations was relatively easy, the same didn't happen with the municipal services in many Municipalities, which saw these services as an important source of revenue and power, and resisted to the integration, in some cases, until to the beginning of the 1990s.After nearly three decades of implementing Law2002, all indicators in the electricity sector had incomparably greater values, whether they were on the installed capacity, the electricity production, the consumption per capita or on the exploitation of national resources in electricity generation. The concentration of the electricity sector in EDP, culminates the process of the State intervention, that began to rise in the 1940s. [ABSTRACT FROM AUTHOR]