This paper presents a new approach for harmonic analysis in a three-phase power system. Harmonics free system voltages v(t) or currents i(t) form a closed loop in voltage-voltage or current-current plane. In this loop cleavages appear with the presence of harmonics, order of which is directly proportional to number of cleavages. Reactive and active power of the system are related with the area in v-i and vi-t planes covered by the curves consisting of fundamental waveform along with harmonic components, wherefrom, active power, reactive power and total harmonic distortion factors have been measured. Park transformation technique has been used for power distortion factor measurement, which has reduced the computational effort to a great extent.