GTI non linear load

[electrofelon]

We have an installation where due to the wiring method, it is important that the neutral of the 3 phase inverter output circuit(s) is a non current carrying conductor per 310.15(B)(5). This hasnt been inspected yet, but I am a little paranoid. Any advice on what I can tell the inspector if he says something like "its electronic so its non linear" or "prove to me that it is a linear load". The manufacturer states: "Harmonics <3%" Does that do it?

 

[Ingenieur]

that should satisfy him if he even brings it up

 

[Besoeker]

We have an installation where due to the wiring method, it is important that the neutral of the 3 phase inverter output circuit(s) is a non current carrying conductor per 310.15(B)(5). This hasnt been inspected yet, but I am a little paranoid. Any advice on what I can tell the inspector if he says something like "its electronic so its non linear" or "prove to me that it is a linear load". The manufacturer states: "Harmonics <3%" Does that do it?

GTI in this context?

 

[wwhitney]

Grid Tied Inverter

 

[Besoeker]

Grid Tied Inverter

Thank you kindly, sir.
Such as might be used for photo-voltaic applications?

 

[electrofelon]

Thank you kindly, sir.
Such as might be used for photo-voltaic applications?

Yes sir.

Thanks for the replies, I feel better about it now.

 

[Ingenieur]

it's likely coupled to the grid with a xfmr which will lower it further

 

[Besoeker]

it's likely coupled to the grid with a xfmr which will lower it further

Possibly there is for isolation and voltage matching but wouldn't such a transformer be considered part of the GTI system and thus already included in the calculations?

Some we did (not PV) had to feed the grid at 3.3kV. This was achieved by taking the inverter output through a step up transformer. Calcs for losses and harmonics took that tranny into account.

Maybe it's different for PV.

 

[electrofelon]

it's likely coupled to the grid with a xfmr which will lower it further

Possibly there is for isolation and voltage matching but wouldn't such a transformer be considered part of the GTI system and thus already included in the calculations?

Some we did (not PV) had to feed the grid at 3.3kV. This was achieved by taking the inverter output through a step up transformer. Calcs for losses and harmonics took that tranny into account.

Maybe it's different for PV.

Practically all String inverters are transformerless now. I Cant really speak about central inverters since I dont come across those much (unfortunately). Typically what Isee for systems up to several MW is 480 string inverters. Facility takes service at 480. Utility provides transformer from their system, usually 7.2/12.47 or 7.62/13.2. I am not sure how it is typically done in those really large systems.

Edit to add: Sometimes the customer will transform the inverter output. Most commonly this happens if they have a 120/208 service since there is much less choice in 208V inverters.

 

[Besoeker]

Practically all String inverters are transformerless now. I Cant really speak about central inverters since I dont come across those much (unfortunately). Typically what Isee for systems up to several MW is 480 string inverters. Facility takes service at 480. Utility provides transformer from their system, usually 7.2/12.47 or 7.62/13.2. I am not sure how it is typically done in those really large systems.

Edit to add: Sometimes the customer will transform the inverter output. Most commonly this happens if they have a 120/208 service since there is much less choice in 208V inverters.

Not my field so thank you kindly for the education and edification.

 

[electrofelon]

Not my field so thank you kindly for the education and edification.

I just looked at Yaskawa central inverters, and they put out 380V, must make you feel warm and fuzzy inside yes?

 

[Besoeker]

I just looked at Yaskawa central inverters, and they put out 380V, must make you feel warm and fuzzy inside yes?

It might if we has a 380V system............

 

[electrofelon]

It might if we has a 380V system............

Oh are you the 415 folks?

 

[Besoeker]

Oh are you the 415 folks?

Nominally 400/230V. Supposedly "Harmonised" in the EU.

 

[electrofelon]

I thought there was not actually such thing as 400, it was either 380 or 415?

https://www.schneider-electric.co.uk/en/faqs/FA163890/

 

[Besoeker]

I thought there was not actually such thing as 400, it was either 380 or 415?

https://www.schneider-electric.co.uk/en/faqs/FA163890/

That's why I said "nominally" in my previous post.
More nonsense imposed by the EU. It's being going on for decades.

 

[steve66]

Electronics normally cause harmonics on the input side.

On the output side, the load will mostly determine if there are any harmonics present.

 

[Besoeker]

Electronics normally cause harmonics on the input side.

On the output side, the load will mostly determine if there are any harmonics present.

The input is DC and the output is the grid in this case.
If the grid is fairly stiff, as it usually is, one might assume that the concern is over current harmonics being injected into the grid.

 

[Sahib]

If the grid is fairly stiff, as it usually is, one might assume that the concern is over current harmonics being injected into the grid.

If OP does not have equipment like harmonics analyser at hand to prove that, one easy to prove it, IMO, is to measure with a simple voltmeter to see whether 1.732 times phase voltage= line voltage, which would not be the case if voltage harmonics is present.

 

[Besoeker]

If OP does not have equipment like harmonics analyser at hand to prove that, one easy to prove it, IMO, is to measure with a simple voltmeter to see whether 1.732 times phase voltage= line voltage, which would not be the case if voltage harmonics is present.

As I posted, I think the concern would be current harmonics.