Harm of Harmonics to Electric Power and Electrical Equipment (III)

6. Interference with weak current system equipment

For weak electrical equipment such as computer networks, communications, cable television, alarms, and building automation, harmonics in the power system are coupled to these systems through electromagnetic induction, electrostatic induction, and conduction, causing interference. The coupling strength between the electric induction and the electrostatic induction is proportional to the interference frequency, and the conduction is coupled through the common ground, and a large amount of unbalanced current flows into the grounding pole, thereby interfering with the weak current system.

7. Affect the accuracy of power measurement

Among the current power measuring instruments, there are magnetoelectric type and inductive type, which are greatly affected by harmonics. In particular, the electric energy meter (multiple inductive type) will cause measurement confusion when the harmonics are large, and the measurement is inaccurate.

8. Harmonics have an impact on the human body

From the perspective of human physiology, when the human cells are stimulated and excited, they will undergo rapid electrical fluctuation or reversible inversion based on the cell membrane resting potential. If the frequency is close to the harmonic frequency, the electromagnetic radiation of the grid harmonics will directly affect. Human brain magnetic field and heart magnetic field.

When the degree of harmonic pollution of the power grid is less than the national standard, it usually does not affect the system. As the degree of pollution increases, the effects of harmonics gradually emerge. In the case of severe harmonics exceeding the standard, if harmonic control is not carried out, it will often have serious consequences. The characteristics of harmonic sources are very complex, because the generation of harmonics depends not only on the load itself that produces the harmonics, but also on the short-circuit capacity of the grid, the composition of the grid, and the nature of other loads in the grid.