Investigations on the impact of voltage and current harmonics on enduse devices and their protection
Abstract
After defining the relation between harmonic voltages and currents through harmonic impedances, the impact of harmonics on electromagnetic enduse devices such as transformers and machines is formulated based on analytical and experimental investigations. A harmonic factor representing the square of a weighted total harmonic distortion factor provides a mechanism for estimating the reduction of lifetime of electromagnetic enduse devices due to additional losses generated by sets of harmonics of frequencies below 2000 Hz. The forces and torques of saturable threephase induction machines during starting and steadystate operation are computed from magnetic field solutions. Within the above frequency range the accuracy of induction watthour meters is reduced and the impact of harmonics or fractional harmonics (which exhibit a frequency other than those of harmonics and subharmonics) on distribution system relays can be severe. Also, the performance of television sets deteriorates for fractional harmonics below 2000 Hz. The impact of harmonics on shunt capacitors limits the harmonic amplitudes with frequencies above 2000 Hz. Depending upon the size of the system impedance either the harmonic voltages or the harmonic currents will be predominant. For small impedances the values of the harmonic currents will be limited by the permissible harmonic current loading of pole and substation transformers, whereas for large impedances the harmonic voltage amplitudes will be limited by the permissible additional losses in parallel connected electromagnetic enduse devices. The propagation of harmonics within a distribution feeder is such that for dispersed harmonic sources of the same kind no significant canceling of harmonic amplitudes occurs. Under certain circumstances the propagation of harmonics within a distribution feeder can cause resonances.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 January 1987
 Bibcode:
 1987STIN...8723878F
 Keywords:

 Circuit Protection;
 Electric Current;
 Electric Equipment;
 Electric Potential;
 Harmonics;
 Power Supplies;
 Capacitors;
 Electrical Impedance;
 Electrical Insulation;
 Induction Motors;
 Television Equipment;
 Transformers;
 Wattmeters;
 Electronics and Electrical Engineering