The need to operate electrical devices the design capabilities of which have been exhausted almost completely under the conditions of more stringent reliability requirements gives rise to increased attention to the development and research of methods for diagnosing the power equipment state. This problem acquires not only a scientific interest, but also practical significance, which follows, in particular, from the mass-scale use of power transformers for operating voltages above 35 kV. One of promising development lines is the method of constructing dielectric absorption spectra, which is based on using the capabilities of isothermal depolarization current measurements. In this case, the information that accumulates as a result of the insulation system’s dielectric medium polarization as a certain number of loosely coupled charges displaced from their locations is adequate (equivalent) to the information obtained as a result of depolarization when measuring the return voltage (RV) value. Owing to the above-mentioned adequacy, it is possible to use the quantity tI(t) as a parameter for monitoring the state of the power equipment insulation system. The spectrum construction algorithm presented in the article is similar to the algorithm for constructing the RV spectrum, but is produced in the course of computer-aided processing of measurement results using the time windows that specify the insulation gap polarization time interval. As a result, it becomes possible not only to produce the dielectric absorption spectrum, but also to calculate the values of the main parameters characterizing the gap state.