Advanced method to identify harmonics characteristic between utility grid and harmonic current sources

This paper presents advanced measurement technology to clarify the interaction between harmonic current sources and utility power systems. Difficulty to solve harmonics problem 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. The authors have developed active harmonic instrument using current injection of inter-harmonic frequency (noninteger harmonics), which exist 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. They have successfully confirmed the performance of this instrument in actual distribution network. This technology will contribute not only to the improvement of power quality of utility power systems but also to be able to clarify distribution of harmonic current in utility power network.