Resource-Saving Overcurrent Protection

Abstract

Construction of relay protections of electrical installations without the use of bulky metal- and insulation-intensive measuring current transformers (CTs) was repeatedly discussed at Conferences of the International Council on Large Electric Systems (CIGRE) as a challenge for the electric power industry. In the article, the authors present resource-saving reed switch current protection for 6–10-kV electrical installations connected to switchgear cells, which is an alternative to traditional protections. The scientific novelty of the work lies in (a) reed switch protection design on the basis of measuring the magnetic induction in different modes and at different points inside a cell, and we prove that inductance values are sufficient to detect phase short-circuits in electrical installations fed from this cell and derive the dependence of the induction on the position of an inductance coil inside the cell; (b) proven possibility of using the simplest formula of the Biot–Savart law for the calculations if the experimentally obtained coefficients are introduced into it; (c) development of a technique for calculating the parameters of the overcurrent protection based on reed switches. Experimental results are presented in graphical form and clearly show the points of EMS maxima and minima. Settings for resource-saving current protection are selected and a feasibility study of the effectiveness of resource-saving overcurrent protection is carried out. A technical and economical assessment of the efficiency of the suggested overcurrent protection is conducted.