Your questions answered: Harmonic distortion essentials and solutions

Discover the essentials of IEEE 519-2022 and how it relates to harmonic distortion in power systems. The recommended practice of this standard offers vital guidance for nonlinear load-inclusive power system designs.

During virtual training week on October 2, the presenters explained the complexities of harmonics in power systems, shared insights into handling nonlinear loads and discussed how various solutions can meet the stringent IEEE 519 standard.

Register for the on-demand version of the “Demystifying IEEE 519-2022: Harmonic Distortion Essentials and Solutions” webcast here.

Additional questions are answered by Dan Schmidt, Global Product Manager, MTE.

Question: Where is PCC located?

Answer: The PCC is the closest point on an electrical utility system where the utility and/or another customer may be affected by harmonics that are generated by another user. If the transformer feeding the user creating the harmonics is owned by the user, the PCC is on the primary side of the transformer. If the transformer is owned by the utility, the PCC is at the secondary side of the transformer.

Question: Does the load side harmonics significantly impact the life of the motor?

Answer: Yes, load side harmonics can significantly impact the life of the motor, especially the motor windings and bearings. Load side harmonics can also impact the life of the cables connected between the VFD and motor. As well as cause electrical interference with sensors and can cause the VFD connected to that motor to trip.

Question: Is motor damage typical with sustained high levels of harmonics?

Answer: Yes, on the load side, high levels of harmonics will typically cause the motor windings and/or bearings to fail prematurely.

Question: Is there no real problem on the load side since the sinewave is essentially recreated from a dc supply?

Answer: On the load side, the VFD output is a pulse width modulated signal that contains voltage harmonics. These harmonics become worse as cable lengths increase. Voltage harmonics can significantly impact the life of the motor, especially the motor windings and bearings. Load side harmonics can also impact the life of the cables connected between the VFD and motors, as well as cause electrical interference with sensors and can cause the VFD connected to that motor to trip.

Question: What if the transformer is provided by the utility company and only serves one client?

Answer: If the transformer is owned by the utility, the PCC is at the secondary of the transformer. While there is not another customer who could be affected by harmonics, the utility will still be concerned with harmonics damaging the transformer and potentially other equipment on the utilities distribution system.

Question: Do you want a reactor, dc choke, passive filter or active filter with every drive?

Answer: A minimum of a line reactor is recommended with every drive. The reactor will not only filter out some of the harmonics (typically reduce the THID down to 30-40%), but more importantly, will protect the drive from voltage transients from the utility.

To what % do reactors reduce the THID?

Answer: Typically line reactors reduce THID to 30 to 40%. A 3% line reactor will reduce THID to about 35 to 40% and a 5% line reactor will reduce THID to about 30 to 35%.

Purpose of line reactor is whether to Protect VFD or block harmonics going to Utility at POC ?

Answer: Both. Line reactors are always recommended to help protect a VFD from voltage transients from the utility. Line reactors will help in meeting IEEE 519 at the PCC.

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