Distributed generators (DG) are scattered throughout the countryside. As a result, they are of relatively small power and should be connected without commutating apparata to low and medium voltage radial power lines. The protection of this power line loses accuracy. To what extent current or distant protection is impaired, depends on many factors. The negative impact of DG is characterized by setting ratio (SR): the relation of current or impedance setting with DG to these quantities without DG. SR depends primarily on DG fault quotients – the fault current of separate DG divided by total fault current of main source and all DG connected to this radial line. Usually DG fault quotients are greater than DG load shares and grow to the end of radial line. SR are worse when fault quotients increase along the line. Head current protection and head distance protection and intermediate distance protections have underreach when DG fault quotients are not very different. For head protection, impedance SR is inverse of current SR and improves when protection is installed nearer to the fault. Current limiting reactors in series with DG improve SR.