Reed Switch Overcurrent Protection: New Approach to Design

Abstract

The problem of getting rid of expensive and metal-intensive current transformers has been declared by CIGRE as strategically important for the electric power industry. However, almost all traditional current protections receive information from measuring current transformers. In this work, a resource-saving reed switch overcurrent protection without current transformers is suggested, which can be used as an alternative to traditional current protections for 6–10 kV electrical installations connected to a switchgear cell. The protection is designed following the novel method we have developed based on inductance coils. Inductance coils measure the electromotive force under different operation modes of an electrical installation and at different points inside the switchgear cell it is connected to; the EMF values are recalculated in the values of magnetic induction, and reed switches are mounted instead of inductance coils at the points where the magnetic induction is maximal. Moreover, these values are sufficient to detect phase-to-phase short circuits in the electrical installation. The dependence of the induction value on the position of an inductance coil inside the cell is derived with the use of the simplest formula of the Biot–Savart law. The results can be used at large and small industrial enterprises, electric power stations, and substations of plants; they can be interesting for the scientific community because they help to solve the topical problem of the electric power industry.