Medium voltage

[ggunn]

Have any of you guys ever designed PV systems that interconnected at medium voltage? If so, where did you pick up the skills necessary to accomplish that? I have looked for training that would apply but so far I haven't found any.

 

[LEO2854]

Have any of you guys ever designed PV systems that interconnected at medium voltage? If so, where did you pick up the skills necessary to accomplish that? I have looked for training that would apply but so far I haven't found any.

How about this....

 

[ggunn]

How about this....

Thanks for the link. I found them yesterday; I plan to talk to them, but the wording on that page implies to me that having them build a custom course for me would be expensive. Perhaps prohibitively so.

 

[69gp]

Have any of you guys ever designed PV systems that interconnected at medium voltage? If so, where did you pick up the skills necessary to accomplish that? I have looked for training that would apply but so far I haven't found any.

Medium voltage interconnections are no different than a medium voltage system feeding a commercial or industrial building. You have your medium voltage cable feeding a transformer. From the transformer out you would have your secondary.

 

[ggunn]

Medium voltage interconnections are no different than a medium voltage system feeding a commercial or industrial building. You have your medium voltage cable feeding a transformer. From the transformer out you would have your secondary.

Those are the fundamentals, yes, but the devil is in the details.

 

[69gp]

Those are the fundamentals, yes, but the devil is in the details.

what is it you are looking to learn? how to design a system? From my experience there is no difference in the way they are wired.

 

[GoldDigger]

what is it you are looking to learn? how to design a system? From my experience there is no difference in the way they are wired.

If you only have to interface with the 240V secondary of an existing transformer, there is no difference from a 240V service. If you are installing the MV transformer, then it is a lot different.

 

[ggunn]

If you only have to interface with the 240V secondary of an existing transformer, there is no difference from a 240V service. If you are installing the MV transformer, then it is a lot different.

Exactamundo. If all you have to do is land your 480V (or whatever) on the LV side of an existing transformer to MV then it's no biggie. If you have to design the MV circuit itself then it's a different animal. MV MDP's and switchgear are not simple beasts to deal with, and design errors can be very expensive and dangerous.

 

[69gp]

If you only have to interface with the 240V secondary of an existing transformer, there is no difference from a 240V service. If you are installing the MV transformer, then it is a lot different.

That is why I asked the question of what are you trying to do. I have seen 10 meg sites with no medium voltage switchgear other than a pole operated air break and a pad mount transformer. The owner re-closure control done on the 480 volt switchgear. The power company has their re-closure control typically on a pole. I have also seen smaller 1.5 meg sites with MV gear mounted on a pad controlling individual pad mount transformers or wired in radial. A lot depends on how much the customer wants to be able to control remotely and what the utility will allow and not allow.

 

[ggunn]

That is why I asked the question of what are you trying to do. I have seen 10 meg sites with no medium voltage switchgear other than a pole operated air break and a pad mount transformer. The owner re-closure control done on the 480 volt switchgear. The power company has their re-closure control typically on a pole. I have also seen smaller 1.5 meg sites with MV gear mounted on a pad controlling individual pad mount transformers or wired in radial. A lot depends on how much the customer wants to be able to control remotely and what the utility will allow and not allow.

Last year I worked on a response to an RFP for a multi MW PV system at an airport. The interconnection point was to be a backfed breaker in a massive medium voltage MDP. That kind of interconnection is neither simple nor cheap. I no longer work for the company who was (maybe still is) going after that job, so I don't know how it turned out.

I am a PE in Texas in the process of registering myself as a Sole Practitioner with the PE board, and I have been asked if I could seal PV systems which are interconnected at medium voltage. At this point I have to say no because I don't know enough about it. I understand the fundamentals but the specifics can get complex.

 

[Smart $]

...
I am a PE in Texas in the process of registering myself as a Sole Practitioner with the PE board, and I have been asked if I could seal PV systems which are interconnected at medium voltage. At this point I have to say no because I don't know enough about it. ...

JMO... I don't think there is any large scale training available for MV PV systems. I'd say the only place you can look for such is through the manufacturers of MV rated PV eqiupment. Other than that, if you want to fast track your MV understanding, look for a "less specific" MV electrical engineering course. Also study Code requirements for over 1kV systems.

 

[ggunn]

JMO... I don't think there is any large scale training available for MV PV systems. I'd say the only place you can look for such is through the manufacturers of MV rated PV eqiupment. Other than that, if you want to fast track your MV understanding, look for a "less specific" MV electrical engineering course. Also study Code requirements for over 1kV systems.

Thanks; that is what I have been doing. I am also going to talk to someone at the electricians' union to see if they have any suggestions.

 

[69gp]

Last year I worked on a response to an RFP for a multi MW PV system at an airport. The interconnection point was to be a backfed breaker in a massive medium voltage MDP. That kind of interconnection is neither simple nor cheap. I no longer work for the company who was (maybe still is) going after that job, so I don't know how it turned out.

I am a PE in Texas in the process of registering myself as a Sole Practitioner with the PE board, and I have been asked if I could seal PV systems which are interconnected at medium voltage. At this point I have to say no because I don't know enough about it. I understand the fundamentals but the specifics can get complex.

I can see where your coming from now. I thought you were an electrical contractor more or less looking for info on install. Your a step above me my friend. The airport project seems to be pretty involved. I am sure you could do a small basic system as previously I mentioned. A few poles with some equipment mounted than the pad mount transformer. If needed I do have some prints from projects I have worked on that I could forward to you.