Advanced technology to identify harmonics characteristics and results of measuring

This paper presents the advanced measurement technology to clarify interaction between harmonic current source and utility power systems. Difficulty in solving harmonics problems is, as a well-known fact, originated with the difficulty to clarify cause and effect between harmonic source and utility power systems. If we could measure harmonic current of inflow to load side from utility power network and outflow to utility power network from load side, the harmonic problem will be easily solved and prevented. Many kind of harmonic instruments are being used, however, no practical technology has been provided so far. We have developed an active harmonic instrument using current injection of inter-harmonic frequency (noninteger harmonics), which exist in small amount in utility power systems. The active harmonic instrument can measure harmonic impedance for power supply side and load side individually and clearly discriminate between inflow of harmonic current to load side and outflow to power supply side from loads. Since successfully confirming the performance of this instrument in an actual distribution network the authors have carried out field tests in distribution networks located in industrial area, residential area and commercial area, and succeeded in determining their precise characteristics.