When designing the substation, special attention should be paid to the development of the system of own needs, since the reliability of the equipment depends on the correct operation of their own needs. The main task when designing your own needs is the correct determination of the load, which depends on the number and power of transformers, type of substation, type of operating current, type of switches and so on. In order to speed up the process of calculating the load in the work, it is proposed to use a database containing information about all the loads of their own needs, as well as electrical devices necessary for the design of the system. In addition, the database contains data on operational current systems. In this paper, it is proposed to carry out computer-aided design of the substation's own needs system based on algorithms implemented in the original CAD switchgear software. This will accelerate the design process and eliminate errors and inaccuracies, as well as save the design engineer from routine work. The work is carried out with the financial support of a grant from the President of the Russian Federation for young scientists - candidates of sciences MK-939.2019.8.