Up until recently, disturbance recorder utilized in electric energy sub-stations were based on analog circuits and the plotting was done by oscilographs that utilized photo-sensitive paper or graph paper. As a result, these instruments provided a plotting of the kinds of waves of tensions and current of the pre-fault and of the fault. However, because of the technology that was used, it was not possible to get either precision of the monitored data (tension/current) or information about harmonic elements present in the system. Due to the development of data acquisition systems based on microprocessors, new disturbance recorders have been developed with the following characteristics: greater precision in acquisition of the data; integration of the functions of registers and various calculation; transfer of acquired data to the center of analysis through a communication system; storage of data in mass memory (tape or disc) for later mathematic manipulation by computer; systems of auto-diagnosis and auto-monitoring of hardware and software failures, etc. This work presents a few programs of post-processing that utilize data acquired by the disturbance recorder providing a fast, low-cost way to get information such as: the kind of failure that occurred; symmetrical components of positive, negative and zero sequences; harmonic components from the spectral analysis of the acquired data; localization of failures on LT`S, indicating the distance of the point of failure. Several test programs were developed to prove the proposed algorythms, including the utilization of EMTP (Electromagnectic Transient Program) and a unit of acquisition ARTUS.