Correct identification of the harmonic source is important for harmonic responsibility sharing and mitigation. A single-point identification method of harmonic source is proposed based on the concept of harmonic apparent power recommended by IEEE 1459. According to the superposition theorem

the harmonic apparent power caused by the system side and the customer side is defined separately

then the location of the dominating harmonic source can be determined(the system side or the customer side)by directly comparing the sizes of the two values. This method can consider the combined influence of multiple orders of harmonic voltage and current. Simulation on an IEEE 13-bus test system and actual steel plant test has verified the rationality of this method. This work is supported by State Grid Corporation of China(No. SGRI-DL-71-15-006).