Microprocessor relay protection devices have the ability to reprogram the implementation of certain functions without changing the composition of hardware and implementation of algorithms for the detection of complex damage, automation of diagnostic processes and hardware adjustment. Research and justification for the correct setting up of microprocessor terminals used in high voltage switchgear systems at power supply facilities is an important stage for servicing, and in the future, increasing the reliability of each element's operation in particular, which will affect the uninterrupted power supply. The purpose of the study is to substantiate and investigate the operation of the microprocessor device in the conditions of changing the load of consumers. In this article, the rationale and analysis of the operation of the PC-83A2.0 microprocessor device under conditions of changing the power of the consumer is carried out. In particular, the device was studied using Codis and RZA Oscillog software, which allows for setting the relay protection and automation systems in high-voltage switchgears of the power supply system, in particular, setting current values, displaying information on the device board, controlling the switch and other parameters. A description and analysis of the software menu operation has been carried out; individual characteristics of the oscillograms are shown when the load of the power supply object changes. In particular, telecontrol modes were investigated using the indicator relays, the operation of the device's discrete inputs was analyzed. The work uses research and analysis of configuration, measurement and control. Constructed vector diagrams of consumption currents. The study of phase currents and zero-sequence current 3І0н. According to the operation of the relay built a normal inverse characteristic. A thermal characteristic was also constructed with a partial memory of the device (according to IEC 255-8) with a pre-emergency current equal to 80 % of the set current. The above expressions allow to determine the response time of the current protection in accordance with the normally inverse and thermal characteristics. Settings and settings in the microprocessor device can be done individually in the device menu by the buttons on the front panel, as well as from the program "Codis" individually for each parameter or downloading the entire set of arrays of settings and files in the device memory. In all configuration modes, setup, debugging and checking of the device, its communication with the computer and the top-level program is carried out through the local information network with the RS-485 interface or the USB port on the front of the device. The use of such a microprocessor terminal will enable the correct and detailed analysis of the work of relay protection and automation of power supply systems.