High impedance fault HIF produced when an energized conductor falls and contact with an objects have high impedancelike: tree limb, concrete walls, or falls down to the ground. The importance of these undetectable faults isrepresent a safety hazard, also a risk of arcing that causes ignition of fires. This type of fault is cannotbe detected by overcurrent protections. The techniques of detecting HIFs are depending on harmonicanalysis of the line current.In this paper, aproposed techniqueuseddepending on themeasure of the 3rd harmonic.Takagi-Sugeno fuzzy controller is proposed and the rules are trained off-line. The practical results show the ability of the controller to detect and distinguish the HIF with high accuracy.The magnitude and angle of 3rd harmonic were 1% of fundamental and 800respectively. The experiment results obtained using the NI 6250 data acquisition board and Matlab real time toolbox.