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Old 04-08-2016, 08:53 AM   #1
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Default Connecting Grid-tied, PV system to the electrical system

Hello,

I wanted to inquire, whether it would be recommended to feed the Grid-Tied PV system back in the electrical panel which are either backed-up by emergency generator or panel receiving stepped down voltage from a higher voltage source.

Our facility has 1200A, 3-phase, 575V, electrical system. Lighting and other standard 120/208V electrical services are provided via step-down transformer(s) further downstream in the electrical system. The facility also has a 70kW, 3-phase, 575V, emergency generator.

Based on our evaluation, it may be feasible to install a 3 kW, 3-phase, 208V, 10-panel, Grid-Tied, micro-inverter based, PV System in the facility. We need to provide a 20A,3-Pole breaker in one of the 120/208V electrical panel which connects to the PV system. I have the following queries on the two (2) scenarios:

1. Install 20A, 3-Pole breaker in a generator backed electrical panel
- Is it recommended to install such a PV system in a generator backed panel?
- During a power outage, the PV system should de-activate because it is mirco-inverter based. But if the panel is backed up by the generator and is energized during a power outage, would it be a safety concern as the PV system installation i.e. would be be re-energized?

2. Install 20A, 3-Pole breaker in the 120/208V electrical panel which receives stepped-down voltage from 575V system
- Is it recommended to install such a PV system in an electrical panel which recives stepped-down voltage?
- Some step-down transformer manufacturers do not recommend feed back into the transformer, so would connecting a PV system be a safety issue or lead to void of any standards ratings?

I'd appreciate your comments or suggestions on this issue.

Thank you.
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Old 04-12-2016, 10:12 PM   #2
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The recommendation not to backfeed a transformer is usually based on not supplying magnetizing current from the wrong side. Not a problem with GTI.
Do not hook a normal GTI to a generator!
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Old 04-12-2016, 10:13 PM   #3
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The recommendation not to backfeed a transformer is usually based on not supplying magnetizing current from the wrong side. Not a problem with GTI.
Do not hook a normal GTI to a generator!
Instead connect it upstream of the transfer switch.
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Old 04-13-2016, 12:00 AM   #4
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3kW solar system seems like too small to even bother with. I'm off grid with a 3kW system for my house. But if I was going to do it, it would be a second service from the utility at 480 volt 3 ph. Sized to give you room to grow. You drop the micro inverter idea, and install a 480 volt 3 ph inverter(many manufacturers out there) through a disconnect/panelboard. Set it up to allow you to add on more panelboards.

By the way, all grid tie systems backfeed through a transformer(PoCos)
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Old 04-19-2016, 12:33 PM   #5
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Thank you very much for your inputs.
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Old 06-15-2016, 10:39 AM   #6
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Is it too late to reply? Yes Phase perfect can help you in insuring going back to single phase then use ABB to step up to a high voltage grid.
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Old 06-15-2016, 10:58 AM   #7
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I would also recommend using natural gas generators, and using waste heat for heating, since you are in Canada natural gas heat pumps and air conditioning is legal there. Here in the states we have forgotten much of what was in the Magna Carta when Jeffersonian Democracy died. Our prison are run by cooperation, cities are incorporated and we live in home owner association manages by a cooperation. The whole idea of townships is in rural country side where some electrical co-op survive. We spend more money on prison then we do for education.
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Old 06-15-2016, 11:08 AM   #8
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The 575 Volt system is due to the voltage drop from the 600 volt generator that is placed on the motors you use. While here in the states and part of Canada 480 3 phase and 120/240 split phase are used as while as the 120 single and 208 3 phase more for commercial locations.
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Old 06-15-2016, 11:37 AM   #9
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The 575 Volt system is due to the voltage drop from the 600 volt generator that is placed on the motors you use. While here in the states and part of Canada 480 3 phase and 120/240 split phase are used as while as the 120 single and 208 3 phase more for commercial locations.
No, 575 3 ph is a normal power system used by many Canadians and also used by older American paper mills. It has nothing to do with voltage drop of a generator.
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Old 06-15-2016, 03:37 PM   #10
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No, 575 3 ph is a normal power system used by many Canadians and also used by older American paper mills. It has nothing to do with voltage drop of a generator.
Not voltage drop of the generator but from the lines, It is the range that is important. I have 120/ 240 coming into my house with the transformer right in front. Motors and air conditioners say 230 volt. People talk about 110v 115v and 120v rms when it is really about the same thing. Now I will admit to being in Brazil where they do have 127v rms single and 220 3phase, but everything works find if you plug a hair dyer from here in a 127v no problems. But wait until you take a shower where one of the heating coils burns out and you get a 220v shock, the neutral is not bonded so each leg to ground has 220volts but not a good return path to the secondary of the transformer. Now I have been wrong before I went to Brasilia and my wife plug in her hair dryer with the same type of plug as Sao Paulo. it ran really fast for 15 seconds damn 220v outlet. This is why we have locks to put on boxes. The biggest shock I ever had was working on a dc power supply and not getting one of the four vacuum tubes shorted to ground. Yes the line might be disconnected but isn't it wise from your experience that you make sure every capacitor is discharged?
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Old 06-15-2016, 04:08 PM   #11
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Another thing the old analog meters read volts average the new digital read volts rms and there are always transients. it always + or minus same percent just look at the spec sheets for the inverters that you talk about. If I go out to my car and measure my battery fully charged it going to be more then 12 volts I hope, or my battery is going to make it through the summer.
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Old 06-15-2016, 04:21 PM   #12
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Quote:
Originally Posted by backstay View Post
3kW solar system seems like too small to even bother with. I'm off grid with a 3kW system for my house. But if I was going to do it, it would be a second service from the utility at 480 volt 3 ph. Sized to give you room to grow. You drop the micro inverter idea, and install a 480 volt 3 ph inverter(many manufacturers out there) through a disconnect/panelboard. Set it up to allow you to add on more panelboards.

By the way, all grid tie systems backfeed through a transformer(PoCos)
I hope you are where the grid can handle 480 3 phase. by grid is just spilt phase 120/240 and other 3 phase around here are 120 single/208 3ph. I guess it depends on your location some places may even have a delta 240 3 phase. Most major industries will find the saving on wire size of using 480v to have a lower current. Location location loc...
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Old 06-15-2016, 05:15 PM   #13
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Originally Posted by katwalatapan View Post
Hello,

I wanted to inquire, whether it would be recommended to feed the Grid-Tied PV system back in the electrical panel which are either backed-up by emergency generator or panel receiving stepped down voltage from a higher voltage source.

Our facility has 1200A, 3-phase, 575V, electrical system. Lighting and other standard 120/208V electrical services are provided via step-down transformer(s) further downstream in the electrical system. The facility also has a 70kW, 3-phase, 575V, emergency generator.

Based on our evaluation, it may be feasible to install a 3 kW, 3-phase, 208V, 10-panel, Grid-Tied, micro-inverter based, PV System in the facility. We need to provide a 20A,3-Pole breaker in one of the 120/208V electrical panel which connects to the PV system. I have the following queries on the two (2) scenarios:

1. Install 20A, 3-Pole breaker in a generator backed electrical panel
- Is it recommended to install such a PV system in a generator backed panel?
- During a power outage, the PV system should de-activate because it is mirco-inverter based. But if the panel is backed up by the generator and is energized during a power outage, would it be a safety concern as the PV system installation i.e. would be be re-energized?

2. Install 20A, 3-Pole breaker in the 120/208V electrical panel which receives stepped-down voltage from 575V system
- Is it recommended to install such a PV system in an electrical panel which recives stepped-down voltage?
- Some step-down transformer manufacturers do not recommend feed back into the transformer, so would connecting a PV system be a safety issue or lead to void of any standards ratings?

I'd appreciate your comments or suggestions on this issue.

Thank you.
I would still suggest going to www.phaseperfect.com or seweurodrive.com since any thing of that scale could have enormous energy savings from regenerative loads and insure transient are put back correctly= less noise on line and longer life of equipment plus savings on energy.
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Old 06-15-2016, 07:57 PM   #14
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Quote:
Originally Posted by backstay View Post
No, 575 3 ph is a normal power system used by many Canadians and also used by older American paper mills. It has nothing to do with voltage drop of a generator.
User4818 has a post on Canada 600Volt color code for each of the 3 phases. He already knows what the generator nameplate says. I wanted to refer him to Phase tech so the regenerative loads might be recovered on put back in phase with the line to reduce transients. he would have more information on what the transformer would accept than I would.They know more far more about Canada and the CEC than I do.
Thanks anyway.
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