Background. Transformer power growth in AC low-voltage electrical installations and the need to ensure quick disconnection of remote arcing short circuits require higher accuracy of calculating electric arc resistance in the region of high and low currents. Studies of the existing method show that the range of currents it can be applied to is limited to the values from 0,65 kA to 42 kA, which does not always correspond to the parameters of electrical installations for which the calculation is made. Experts also note the need to exclude the arc length from the calculation and to take into account the ratio of the circuit resistance inductive and active components when calculating the current reduction factor. Experimental studies of arcing short circuits conducted abroad contain data for the range from 20 A to 150 kA for arc burning in various conditions, which makes it possible to increase the accuracy of calculating arc resistance in the region of small and large currents and to improve the existing methods.
Materials and methods. We used the results of experimental studies of arcing short circuits in the range from 20 A to 105 kA for arc burning in different conditions. The experimental data were processed by methods of factor and regression analyzes.
Results. We have developed a method for calculating electric arc resistance, which allows calculations in the range of stable arcing short circuits from 80 A to 50 kA without taking into account the arc length, and also calculation of the current reduction coefficient taking into account the ratio of circuit resistance inductive and active components. The results of applying the proposed method have shown satisfactory agreement with the available experimental data and existing methods in the range of currents determined for them.
Conclusions. The application of the developed method will allow improving the design quality of low-voltage electrical installations with over 2500 kVA transformers and ensuring the instantaneous disconnection of remote arcing short circuits with an electromagnetic release of circuit breakers.