This paper presents a new algorithm based on simultaneous measurements by phasor measurement units in order to detect loss-of-synchronism of generator. The researchers believe that the criteria of equal energy levels and wavelet transformation are preferable to the usual methods, in the sense that in addition to the acceptable speed, their practical use in phasor control centers is also possible. Also, the two basic challenges of these methods, i.e. equalization of the network in the form of a two-machine model and estimation of the generator state in the time after the fault, have been solved. The importance of converting the power network to the two-machine equivalent network must be done adaptively and online, because the structure of the power network is not constant due to changes in the state of entry and exit of equipment. In this paper, with the help of the simultaneous information sent from the phasor measurement units installed in different points of the network, the equivalent circuit of two- machine of the power system has been calculated from the point of view of each power plant unit. Based on this and by using the developed equal levels criterion method which is introduced and developed in the paper and the wavelet transform, both in the local mode and in the wide measurement mode, there are methods to detect and predict the loss-of-synchronism is provided. In each section, the presented algorithm is tested on a standard network (preferably IEEE standard networks), for various situations of errors occurring in the system, and its results, both in terms of performance speed and accuracy, with usual industrial methods, which are impedance relays, have been compared تفاصيل المقالة