TRANSFORMER'S. STEP UP TO STEP DOWN

[streeta]

Anyone
Currently our set up is we have 2 33Kv to 415Kv Tx supplying the plant. When we have a power outage we run on gensets. These gensets are cabled straight into the MCC so do not go through the transformers. What i would like to do is use the transformers as step up Tx's, step the 415 from the gensets to 33Kv and send this to our housing estate where it will be steped down to 415V once again.

However i belive there is a earthing problem with doing this. Is this because you do not have a proper earth running from the supply (gensets) to the end user. As the transformer acts as a isolating Tx. Will i have to run a earth cable from the gensets to the end point. which is about 1 to 2 Km away.

Thanks
Greg

 

[busbar]

{Assumed posted ‘415kV’ is intended as 415V} The described scenario may be possible considering a couple of points… The ‘facility’ [non-utility-owned equipment and lines] would need to be tied to the serving utility, typically at a point “upstream” of the described 33kV components. This would make your firm (in North American parlance) a ‘self generator,’ and the interconnect requirements with the serving utility—particularly with respect to protective relaying, would likely significantly change. If they are not currently in place, associated contractual arrangements with the serving utility may also have to be renegotiated.

As for a metallic return path for 33kV grounding, that is not automatically required given proper 33kV system grounding and coordinated ground-fault overcurrent protection. As to the feasibility and economy of the proposed change—loadflow, protective coordination and grounding studies would be in order.

 

[alehman]

You should be OK with the utility company as long as you completely separate from them and don't back-feed any utility-owned equipment (the 33kV lines would need to be owned by the customer).

If some of the equipment is owned by the utility or you plan to operate in parallel with the utility, the protection requirements mentioned by busbar come into play. That can be costly.

One legal factor - in the U.S., if the power you generate crosses property boundaries you will technically be classified as a utility company and the local or state government may object.

 

[davidbeach]

"One legal factor - in the U.S., if the power you generate crosses property boundaries you will technically be classified as a utility company and the local or state government may object."

If that is ever a true statement, it must be on a state-by-state basis. Having worked on several projects with the capability of exporting customer generated power to the serving utility I have never run across that notion. I have also never heard of it in any of the classes I have taken on, or including, distributed generation. So it certainly is not true in Oregon, nor could it be very widespread.

 

[engineerkribhco]

There may be other consumers connected with the 33KV line.So how do you ensure that the 33KV power supply fed into the utility grid by step up transformers will reach to
housing estate only.It would be much better option to lay dedicated cables from Gensets to the housing estate Power Control Centre.