VFD's & IEEE 519

[rwilsond]

I'm involved in the selection of VFD's for some large AC motors (up to 450HP). The spec that was given to the supplier imposes the requirement that these VFD's "shall meet all requirements of IEEE Std 519".

I have IEEE Std 519 ("Recommended Practices and Requirements for Harmonic Control in Elect Power Systems"), and have read through it. But I do not see "requirements"; it seems to be nothing more than suggested guidelines.

So, what is there in IEEE Std 519 that can be considered to be REQUIREMENTS?

 

[charlietuna]

the vfd manufacturer will be the one to ask since this is a manufacturering spec.

 

[ron]

519 establishes harmonic limits at the point of common coupling which is usually the utility meter. They need to know a lot about the entire facility to provide compliance with 519 as it is not a device specific requirement but for the facility.
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[wirenut1980]

If I had to guess, they are probably referring to individual harmonic content and/or overall THD. I thought those were listed in tables. My copy of the standard is a work, otherwise I would look up the values.

Plus ask whoever wrote the spec.:smile:

Edit: Ron's got ya covered.

 

[brian john]

If I had to guess I would bet it is a spec thrown in because it was there. And the specifier has always used this particular spec.

I just read a spec for a parking garage 1132 pages mentions specifications for pieces of equipment that are not on the project, never will be unless the garage is modified into a different use.

 

[jim dungar]

It is very common for specifiers to require that VFD meet IEEE 519. But, as it has been pointed out, IEEE 519 is for a facility not an individual piece of equipment. I believe this type of spec is often ignored as it is clear the specifier is simply "cutting and pasting" rather than designing.

How expensive is it to provide the filtering to reduce the input harmonics of each VFD, when 15 of them are mounted in a single motor control center? Wouldn't it be better to limit the harmonic content at the incoming lugs of the MCC instead? How much of a problem is caused by a 480V 100HP VFD with 20% THD if it is fed by a 1000KVA transformer whose remaining load is 600KVA of SCR controlled heating equipment?

 

[brian john]

480V 100HP VFD with 20% THD

20% current THD

 

[weressl]

I'm involved in the selection of VFD's for some large AC motors (up to 450HP). The spec that was given to the supplier imposes the requirement that these VFD's "shall meet all requirements of IEEE Std 519".

I have IEEE Std 519 ("Recommended Practices and Requirements for Harmonic Control in Elect Power Systems"), and have read through it. But I do not see "requirements"; it seems to be nothing more than suggested guidelines.

So, what is there in IEEE Std 519 that can be considered to be REQUIREMENTS?

The 'suggested guidelines' become 'requirements' when a specifier chooses to do so.

This type of documents developed when there is no overwhelming manufacturing and/or user support to comply with all the requirements, so manufacturers and users can pick and choose. Even if the document is called a Standard such as IEEE841, you may find various levels of compliance with its requirements since there is no thrid party, independent verification exist for it.

 

[rwilsond]

Thanks for the replies; they were very useful.

FYI - the two largest VFD's (for 450 HP motors) will be part of a 44-ton capacity bridge crane. I'm simply providing a 5 kV feeder to the 1600 kVA transformer that rides with the bridge (this transformer supplies all power to the bridge crane). The feeder runs several hundred feet to my MCC. I will consider my MCC bus to be the Point of Common Coupling (PCC). So, I will understand that once all is installed and in operation, the harmonic distortions, at this PCC, should be within the limits of Chapter 10 of IEEE Std 519.

Feel free to let me know if I got it wrong.

 

[winnie]

I think that you are going to have to get the customer to make that determination.

As I understand IEEE 519 (which is minimally), the point of common coupling is generally where the utility meters the supply to the plant.

So one very plausible interpretation is that the harmonic loading added by these drive shall not cause the _entire plant_ to exceed the specified harmonic limits. The best analogy that I can think of is one of adding a large piece of equipment, and being required to insure that this doesn't cause the service to exceed its capacity.

Unfortunately, this interpretation can open up a very large can of worms. For example, what happens if the plant already exceeds the specified harmonic limits, or is close to the edge.

The limits of IEEE 519 are often mistakenly applied to the individual piece of equipment. Certainly that requirement can be met, for a price, but it is often an un-needed expense.

-Jon

 

[rwilsond]

The bridge crane (including its 1600 kVA transformer and VFD's) will be a very small part of this yet-to-be-built plant (which will use more than 100 MVA overall), and I doubt it would have a significant contribution on the overall power system distortion.

So, I must somehow simplify this issue with the crane bidder, and focus on a localized area about the PCC (i.e., MCC bus). I am considering providing them with some estimated info: the available short circuit at the PCC; the size & length of the 5 kV feeder from this MCC to their 1600 kVA transformer; and the demand load of this MCC on its upstream transformer.

Would it then be meaningful and reasonable to ask this vendor to provide their estimated contributions to distortion at this MCC (disregarding the contributions from other sources, since those contributions are beyond their scope)?

 

[weressl]

Thanks for the replies; they were very useful.

FYI - the two largest VFD's (for 450 HP motors) will be part of a 44-ton capacity bridge crane. I'm simply providing a 5 kV feeder to the 1600 kVA transformer that rides with the bridge (this transformer supplies all power to the bridge crane). The feeder runs several hundred feet to my MCC. I will consider my MCC bus to be the Point of Common Coupling (PCC). So, I will understand that once all is installed and in operation, the harmonic distortions, at this PCC, should be within the limits of Chapter 10 of IEEE Std 519.

Feel free to let me know if I got it wrong.

On that size ASD's you can specify 12 pulse rectifiers that will siginificantly reduce your harmonic loading and the 'K' duty on your transformer.

 

[petersonra]

The bridge crane (including its 1600 kVA transformer and VFD's) will be a very small part of this yet-to-be-built plant (which will use more than 100 MVA overall), and I doubt it would have a significant contribution on the overall power system distortion.

The transformer itself may well significantly reduce the amount of harmonics reflected back to the utility.

Place I used to work had a wonderfully written paragraph about these kinds of things. I wish I could remember how is was phrased, because it was both inoffensive and quite clear that we felt a lot of the standards mentioned in the spec did not apply to the piece of equipment we were bidding on.

I don't know how many times I have seen a spec that says something like "the equipment shall comply with NEC". How can a piece of equipment comply? The installation can, but not the equipment itself, except for some very minor things here and there.

One of the ones I got a kick out of was the reference to SSPC standards for painting prep work. The standard referenced was basically just a listing of the ways you could do it, and included options ranging from nothing, to blasting, with no guidelines as to which option was appropriate in any particular case. I have even seen this one referenced in control panel specs where they require you to use a Hoffman enclosure.

 

[rwilsond]

The first thing that comes to my mind are the required "Markings" on equipment, such as Industrial Control Panels, where the SCCR (and other info)is required on these panels via Article 409 of the last two editions of the NEC.

Back to IEEE Std 519: Thanks for the insight. I too wonder how effective the transformer is at isolating the harmonics to the vendor-supplied equipment side (any harmonic effect from the vendor-supplied equipment must pass through the transformer to get to my power system).

 

[Mike01]

Ieee 519

Ieee 519

I agree it sounds to me like the xfmr. will mitigate the majority of your harmonics, you could always provide 18-or so pulse drives with line reactors, or even harmonic midigation devices like active filtering (AccuSine). Also have the engineer define the PCC (point of common coupling) some define the point at the MCC where the motor receives it?s supply some take it back to the service. IEEE 519 identifies guidelines for total harmonic distortion most of the time I have run into this it was indicated in the specifications for the manufacturer to provide and show compliance with IEEE 519 however they will need to know the PCC and have a one-line diagram to start the process also the available fault current and x/r.

 

[beanland]

Contractor Spec

Contractor Spec

If the spec that was given to the supplier was part of the general specifications for the project that the general contractor must meet, the general contractor must meet IEEE 519 in the finished installation. This means that the equipment provided must work in the finished installation to comply. The correct specification is that "the load imposed by the VFD shall not exceed IEEE 519 for a source impedance of xx Ohms." That can then be used by the VFD vendor to set THD limits on the VFD current. IEEE 519 basically limits voltage THD to 5% (varies by service voltage.) The current THD needs to be low enough to keep the voltage THD below the IEEE 519 limit for the specific installation.