Statistical analyses of the distribution and the annual trend of harmonic voltage in Japan

The limits for harmonic currents injected into the public electric power supply system were prescribed in Japan in 1994. It is important to ascertain the effectiveness and sufficiency of these limits. Harmonic voltages at the same bus bars at several substations have been measured since 1994. In addition, a special extensive survey of harmonic voltages was carried out in 2003. This paper analyzes the survey data and clarifies the following points: (1) the existing limits are effective and the harmonic voltage levels have recently been decreasing, (2) the distribution of voltage distortion is similar to the logarithmic normal distribution and there are very few areas where the harmonic voltage distortion is larger than the compatibility levels.