Medium Voltage Switchgear Sizing

[DMG_1]

Does anyone have a link to documentation that discusses sizing of Medium Voltage Switchgear?

 

[Jraef]

Does anyone have a link to documentation that discusses sizing of Medium Voltage Switchgear?

What do you mean by sizing? Physical dimensions?

 

[DMG_1]

For example, let's say that I have a transformer, 10 MVA, 4160 V on the secondary side. I would like to size switchgear for this application.

 

[Jraef]

For example, let's say that I have a transformer, 10 MVA, 4160 V on the secondary side. I would like to size switchgear for this application.

Well, you would size the switchgear for the loads, not for the transformer. But of course you have to take the limits of the transformer into consideration.

 

[templdl]

For example, let's say that I have a transformer, 10 MVA, 4160 V on the secondary side. I would like to size switchgear for this application.

You're getting into some pretty serious stuff. But, here's a place to start:
http://www.eaton.com/Electrical/Consultants/ConsultingApplicationGuide/index.htm

A 10mva is a big honkin' transformer. What is the to feeding the transformer. Would thew transformer be liquid filled ou a dry type? The transformer close coupled to a 4160v med.voltage switchgear lineup, air or vacuum breakers.

 

[weressl]

Well, you would size the switchgear for the loads, not for the transformer. But of course you have to take the limits of the transformer into consideration.

Partially right. You assess the running load and size the transformer for it. You would look at the peak load, emergency load and make sure that the full 65C forced air cooling rating would be able to carry it. That would be approx. 33% above base rating. (From memory). So if you already 'committed' to a 10MVA transformer would require a 2000A gear, but you may chose to go with the 3000A bus, copper is very small cost % of the total gear cost. Use 2000A mains and 1200A feeders. The most important part though is the short circuit bracing and once you committed it is a major cost to upgrade and even worse if you have to replace the gear, even if its FLA rating OK.

 

[dbeasley488]

MV Switchgear Sizing

MV Switchgear Sizing

You might consider breaking up the service into smaller pieces. I.E, split gear up into four units and then locate one unit in each of the four corners of a large building for example. You certainly should also consult vendor for physical sizing per NEC 110. They take more clearance than typical switchboards.

 

[weressl]

You might consider breaking up the service into smaller pieces. I.E, split gear up into four units and then locate one unit in each of the four corners of a large building for example. You certainly should also consult vendor for physical sizing per NEC 110. They take more clearance than typical switchboards.

Actually that is not true in most of the cases.

MV distribution on a large site would warrant this but usually at the next voltage level 13.8kV or even higher. 4160V is mainly utilized for large motors, >200HP, and 480V or 208/120V secondary transformers located at remote or elevated sections of smaller production facility with several plants or single large building.