Power supply reliability level of Latvian distribution network, as well as necessity of introduction of reliability level regulation is evaluated in the doctoral thesis. Existing European performance-based regulation of distribution system operators regarding reliability of power supply is analyzed. Main drawbacks of existing regulation are identified. Power supply reliability indices and their classification methods are investigated and analyzed, pointing to additional indicators that should be used in regulation as well as on methods of classification improvement. Developed questionnaire for customer costs of reliability evaluation. In the frames of doctoral thesis there was performed research, using developed questionnaire, and as the result customer damage functions for Latvian electricity consumers have been created. Methods of power supply reliability evaluation, that can be used for evaluation of technical effectiveness of power suplly reliability improvement activities, have been studied, as well as given reccomendations for practical usage of one of the methods. New algorithms for customer costs of reliability calculations, that are related with reliability of power supply and that take into account time-variable loads and normalized outage costs, and for system operator costs estimation have been developed and proposed in the thesis. Proposed algorithms have been used for practical calculations when evaluating effectiveness of one of the technical reliability improvement activity. On the basis of performed research and analysis, methodology for power supply reliability technical and economical regulation was developed. Doctoral thesis is written in Latvian language, it contains 6 chapters, conclusions and recommendations for further work, list of references, and 3 appendices. Total amount is 156 pages, which include 60 figures and 15 tables, don’t counting figures and tabeles of appendicies. List of references includes 99 literature sources.