It is shown that relay protection and measurement devices for electrical installations with voltages of 6–20 kV can be constructed on the basis of reed relays. To calculate the currents in the busbars at which the reed relays are located, equations are suggested based on the Biot–Savart–Laplace law and the experimentally derived improving coefficients. The method for determining and accounting for interferences acting on reed relays is presented. The sensitivity of reed relays and errors in determining currents according to the equation suggested are estimated.

Keywords: Reed relay, Protection, Measurement, Busbar, Improving coefficient, Error