Analysis of protection criterion values algorithms in case of distorted signals

Nowadays fast increase of nonlinear elements number in the power system is observed. Besides of nonlinear loads there are also new energy sources that require electronic and power electronic equipment. These elements cause distortion of electrical signals and presence of higher harmonics in currents and voltages. Algorithms of protection criterion values are matched to fundamental components of currents and voltages and can cause errors due to these harmonics. In the paper some signals and load models are considered as well as the most influenced criterion values including a few models of a reactive power. As a complement practical model of nonlinear heating system is described and analysed.