Abstract
This article discusses an innovative device designed to determine the value of the steady-state current in the primary circuit of electrical installations using reed switches and a microprocessor without the use of current transformers. The typical structure of relay protection devices is considered. The main elements are presented. When choosing a primary converter, a reed switch was taken, because it has certain advantages over current transformers. As part of the research, experimental installations for measurements were assembled. They made it possible to emulate the real conditions in which the relay protection devices have to function, unnecessary and to depict the characteristics of future devices. The code is presented that allows the microprocessor device to function according to the laid down algorithm. A device on a reed switch and a microprocessor is presented, which allows transmitting a certain amount of current in the primary circuit in digital form (binary code) to the microprocessor protection. The presented measuring device made it possible to implement a method for determining the magnitude of the steady-state short-circuit current.