The parameters of transmission lines, as a rule, are determined by reference data, but during the operation, it might vary essentially from the actual data. There are noted the reasons for the parameters’ modification. This paper explains the opportunity of parameter identification based on the synchronized measurements during the operation of the transmission line. The methods of parameter identification can be classified by various criteria. The diagram of classification was elaborated for the first time. Transmission lines can be represented in the form of quadripole and the Т- and П-forms equivalent schemes, so, applying only the current and voltage synchronized measurement on both ends it is possible to obtain passive parameters of the line. There are presented final formula of six most effective methods for parameter identification of the transmission lines. All analyzed methods were verified with the models of real transmission line. There were compared the results of all proposed methods: the relative errors of calculation for all mentioned methods are less than 1%. The obtained results show the high accuracy of parameter identification for the proposed methods. The influence of measurement errors upon the values of parameters’ results was analyzed in this work. The main contribution of this paper lies in the classification of the methods of transmission line parameters identification and in the research of influence of measurement errors on the results of the parameter identification for transmission lines.