Reconfiguring existing MV Switchgear 1

[rockman7892]

We have a customer asking us to look into re-using an existing 2.4kV switchgear lineup from one location to replace an existing lineup in another location.

In order for this lineup to work in the proposed location it would have to be re-configured so that the sections matched existing main and feeder cables in current locations.

To make this work the switchgear main breaker would have to become a feeder breaker and one of the feeder breakers would need to become a main. Do most swgr manufacturers allow for this change to take place if breakers have proper ratings and proper CT ratios and protection elements are used?

In most 2000A gear can breaker cells typically accommodate either a 1200A or 2000A breaker? If existing cell is 1200A breaker can a 2000A breaker be used with relative ease?

In order to get existing Non-Seg busduct to work with this gear we’d need to make a tap box and transition with cable into gear? Curious to hear what others think of this practice?

 

[Skogsgurra]

This is definitely far from my daily work. But I have got similar questions from factory owners that didn't see the distinction between the risks involved in switching MV at elevated power levels, which this is for me, and the finer points in LV drives.

I have declined any involvement in such things. But there is always someone that thinks he knows it all. One case was when a 36 MW 11 kV electric boiler, fed from a 70/11 kV transformer, was installed and the owner could buy electric energy at a very good price. For the rest of the paper mill, he still paid normal rates.

He then got the idea to put a bridge between the new 11 kV system and the old one, with low-capacity breakers that was fed from an old transformer with something like 3 MW rating. To him, electricity was electricity and Ohms law and all that was all you needed to know about. I stayed away from that.

He then got an "Easterner" (a Russian or Polish) engineer that did the work for him. The whole thing went to ashes.

I can't say that I learned anything from that. But I think that it confirmed that you shall have a little more than Ohm's law in your mental tool box.

Asking the question (OP) is very wise. But I cannot contribute with any advice. There are guys better suited for that in EngTips.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[crshears]

Doesn't sound like a great idea...although probably not un-doable...

How old is the existing switchgear? Will it still meet all applicable codes, and will the AHJ sign off on its re-use?

In my experience the 1200A feeder breakers and 2000A supply/tie breakers have always been of distinctly different dimensions, and therefore physically impossible to swap.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[catserveng]

The best answer to the OP's questions is a lot of "it depends".

I have done a fair number of these type jobs working with engineers who are experienced with MV switchgear work. A lot of things drive the desire to do these type jobs, cost is one factor but in a lot of cases, at least in what I end up dealing with, it comes more to meeting schedules and dealing with long lead times from switchgear suppliers.

On cell size and breaker ratings, mostly I am familiar with 12kV cells, many of the breaker cells are physically the same size, amp rating of the cell depends on bus size, bracing, the thru barrier connections and a number of other factors. The breaker cells usually have a "code" plate that only allows a proper rated breaker to be inserted into the cell. If a proper retrofit is done than the code plate can be changed to allow the different rated breaker to be installed. Usually the code plate is configured to allow a higher rated breaker to go into a lower rated cell, but varies by manufacturer.

Last couple of jobs done reworking MV gear we used cable bus for a number of reasons, ended up being the cleanest way to connect different sections and maintain required ratings.

Not sure where you're at but you may also need to have a field evaluation done after modification to assure conformity, like UL or CSA.

You're best bet may be to seek out a company or engineer who does this fairly regularly to asses your equipment and see if it can be safely done at reasonable cost. There used to be a number of PEARL shops, especially in the USA Southeast, that were very good at coming up with MV switchgear to restore systems after natural disasters.

Hope that helps, MikeL.

 

[thermionic1]

Years ago, I worked for a large OEM switchgear service center. We performed these kinds of modifications all of the time. I recall mating up brand X with Y, uprating bus, uprating bracing, new panel doors with modern protection, all kinds of creative solutions to problems such as yours. As mentioned above, sometimes these modifications were made because the lead time for new gear was too long. We had an Engineering group that worked with the factory to ensure all of the details were worked out ahead of time.

I would recommend you contact your Switchgear OEM and see what they have to say.

 

[cuky2000]

There are many companies that provide service for "custom retrofit MV switchgear". Search the with the key world within the quote and see screenshot below for an example.

 

[LionelHutz]

Do most swgr manufacturers allow for this change to take place if breakers have proper ratings and proper CT ratios and protection elements are used?

There are 2 possible ways to answer to this.

1. The UL or CSA listing plate the manufacturer applies only applies to the gear as it left the factory. The listing no longer applies once anything is changed in the field, and the manufacturer won't be able to list any field changes.

2. You own the gear so the manufacturer really can't allow or disallow what you do in the field. Switchgear breakers are typically bi-directional so you can feed power either direction without an issue.

 

[jraef]

One issue that you might run into however is getting any kind of short circuit withstand / arc resistance / BIL ratings or certification of the of the new configuration. Factory data will only apply to it as it left the factory and if not altered and was properly maintained. Once you change the configuration, you are taking that on yourself.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[Zogzog]

We do this type of modifications all the time, should be simple. Most 1200/2000A cells can be easily changed from one rating to the other by changing the CT's and rejection hardware (And maybe the stabs) What type of gear is it?