Abstarct: Increasing amount of harmonics has been one of the main problems of power quality in power systems in recent years because of growing application of power electronic devices. Harmonics have harmful effects on network equipment and sensitive loads. Therefore harmonic sources and causers of increase of harmonic amounts should be detected. It must be considered that capacitor banks can have a big role on amplifying harmonic quantities. Harmonic sources detection methods are divided into two major groups which are single-point methods and multipoint methods. Multipoint methods are baxsed on the measurements made at several points of system synchronously and require complex and expensive measurement instrumentation. Also one of the two sides of measuring point is determined as the main harmonic source in single-point methods and these approaches give a little information about harmonic state of system. In this thesis an approach is presented for calculation of harmonic contributions in multi-utilities, multi-consumers systems. By using this approach contribution of each branch connected to a feeder of distribution system into voltage and current harmonics can be obtained in each harmonic order. The equivalent impedances of the branches must be known in the presented method. Norton and Thevenin Reference impedances are defined for each branch and an approach to obtain these impedances is presented. By using these impedances as the equivalent impedances of the branches, the contributions of capacitor banks in amount of harmonics can be calculated too. A simulation study has been performed on IEEE 13-bus distribution system with Digsilent software. baxsed on the results the branches responsible for the harmonics because of containing harmonic sources or capacitor banks have been identified accurately by this method.