Decreasing of short-circuit currents in power supply systems enables the usage of less expensive switching-protective devices with a lower breaking capacity and reduction of damage from the consequences of emergency events. In electrical networks of low, medium and high voltage classes, resonant current-limiting devices are used to solve this problem, along with other technical solutions. However, these devices have unsatisfactory weight and dimensions, high cost and other disadvantages. The technical and economic indicators of such devices can be improved through the use of a coil-capacitor (coilcap). Coilcap is a passive element of an electric circuit, which simultaneously possesses inductivecapacitive properties and performs the functions of a reactor and a capacitor in a single technical object. This paper presents a functional diagram of the implementation, design, operating principle and mathematical description of a resonant current-limiting device based on a coilcap. Physical modeling of the steady-state modes of the device (normal mode and current limiting mode) was carried out, and the possibility of limiting short-circuit currents due to the use of a coilcap was confirmed. The practical application of a resonant current-limiting device based on a coilcap can be effectively combined with switching-protective and current-limiting disconnecting devices, relay protection, and automation equipment. © The Authors, published by EDP Sciences, 2020.