MV SWITCHGEAR BUS BAR RATING

[TMMB]

HOW CAN SIZING OF THE MV SWITCHGEAR BUSBAR ACCORDING TO NEC ?, IS THERE IS ANY RELATED ARTICLE IN NEC

PLEASE ADVISE

 

[John120/240]

I have no idea. But shouting is not needed, we heard you. (Turn off all caps)

 

[LEO2854]

HOW CAN SIZING OF THE MV SWITCHGEAR BUSBAR ACCORDING TO NEC ?, IS THERE IS ANY RELATED ARTICLE IN NEC

PLEASE ADVISE

You need to start by reading Article 220........


"CAP LOCKS"?.............:happyno::roll::lol:

 

[templdl]

HOW CAN SIZING OF THE MV SWITCHGEAR BUSBAR ACCORDING TO NEC ?, IS THERE IS ANY RELATED ARTICLE IN NEC

PLEASE ADVISE

Is this a do it yourself job? Otherwise it is built be the manufacturer to ANSI/IEEE with bus based upon ampacity (Cu or Al) and temperature rise and braced for a give short-circuit current.
There are manufacturing standards though. Because it is MV UL may of may not be applicable and I'm not sure if the NEC has an jurisdiction inside the enclosure as are UL listed assemblies. I can't remember any instant where the NEC got involved with MV assemblies.

 

[SG-1]

Bus bar size inside switchgear is determined by building a structure & subjecting it to a heat run test. The bars are loaded to the the rated ampacity & then the temperature is measured over a period of hours or until it is stabilized. The temperature is only allowed to rise by so many degrees above the ambient.

In some cases like 4000A mains, blowers will force cool the 3000A rated bus & breaker.

 

[templdl]

Bus bar size inside switchgear is determined by building a structure & subjecting it to a heat run test. The bars are loaded to the the rated ampacity & then the temperature is measured over a period of hours or until it is stabilized. The temperature is only allowed to rise by so many degrees above the ambient.

In some cases like 4000A mains, blowers will force cool the 3000A rated bus & breaker.

In the gear that I have sold over the past 20 or so years I have never seen a requirement for fans to cool bus in any specs of otherwise.
Selecting a bus size is based upon temperature rise. ntalling bus is based upon the require L-L, L-N, And L-G clearances as well is the insulators and support requirements for fault current bacing requirements.
MV swgr assemblies a manufactured to applicable NEMA/ANSI/and IEEE standards.

Quick Bus Bar Size Selector:
http://www.stormcopper.com/design/Ampacity-Quick-Chart.htm

Aluminum Bus Bar Ampacity
http://www.substationsupply.com/images/PDF's/Aluminum Bus Bar Alloy 6101 Ampacity Chart...pdf

 

[jdsmith]

In the gear that I have sold over the past 20 or so years I have never seen a requirement for fans to cool bus in any specs of otherwise.

For MV metal clad gear covered by IEEE C37.20.2 standard ratings are defined as 1200A, 2000A, and 3000A. Some manufacturers offer 4000A gear that meets the temperature rise requirements by using fans. Most sophisticated customers will not buy this fan cooled switchgear. A similar phenomenon exists for LV switchgear - typical ratings go up to 4000A, but 5000A gear is avaiallble if the user is willing to accept a number of compromises like forced air cooling, uninsulated bus, etc.

Selecting a bus size is based upon temperature rise.

This is correct, but the key is that the temperature rise of the bus is affected by the enclosure and barrier design, that's why the IEEE switchgear standards require a heat run for the whole assembly to take into effect the enclosure without any guessing, rules of thumb, or calculations.

ntalling bus is based upon the require L-L, L-N, And L-G clearances as well is the insulators and support requirements for fault current bacing requirements.

This is essentially correct in that there are rules of thumb for these clearances, but the only requirement in the IEEE standards is that the equipment passes all of the tests, including the BIL test - actual clearances are not specified.

 

[SG-1]

In the gear that I have sold over the past 20 or so years I have never seen a requirement for fans to cool bus in any specs of otherwise.
Selecting a bus size is based upon temperature rise. ntalling bus is based upon the require L-L, L-N, And L-G clearances as well is the insulators and support requirements for fault current bacing requirements.
MV swgr assemblies a manufactured to applicable NEMA/ANSI/and IEEE standards.

I have been testing 4000A forced cooled MV switchgear for 30+ years. Westinghouse DHP type switchgear offered it in both 5 & 15 KV . The 5 KV was 36 wide for both 3000A & 4000A forced cooled instead of the usual 26 inchs wide.

I can say I see more 4000A forced cooled now than ever before. (That said I will not see another one this year.) I have placed the thermocouples for heat run tests & baby sitted the run. The factory where I work is capable of both Heat Run & BIL testing.

The forced air cooling is done with two sets of fans, a primary & a backup. If a primary fan fails a backup takes over & an alarm is sent. If a backup fan fails a second alarm is sent & the customer has 2 or 3 minutes to load shed, or the breaker will trip.

The NEC is not involved with the internal bus of switchgear. As stated before by JD Smith the bar size & clearance is determined by testing.

 

[templdl]

For MV metal clad gear covered by IEEE C37.20.2 standard ratings are defined as 1200A, 2000A, and 3000A. Some manufacturers offer 4000A gear that meets the temperature rise requirements by using fans. Most sophisticated customers will not buy this fan cooled switchgear. A similar phenomenon exists for LV switchgear - typical ratings go up to 4000A, but 5000A gear is avaiallble if the user is willing to accept a number of compromises like forced air cooling, uninsulated bus, etc.



This is correct, but the key is that the temperature rise of the bus is affected by the enclosure and barrier design, that's why the IEEE switchgear standards require a heat run for the whole assembly to take into effect the enclosure without any guessing, rules of thumb, or calculations.



This is essentially correct in that there are rules of thumb for these clearances, but the only requirement in the IEEE standards is that the equipment passes all of the tests, including the BIL test - actual clearances are not specified.

I'm just going by the Westinghouse gear that I sold, both MV and LV the old DHP one of the original VCP, then the VCPW, DS, Magnum DS, etc. I have taken my customers on factory tours and have never seen fans used to cool bus in either indoor/outdoor, or walk in electrocenters. Yesthe original design must be tested to assure that it complies with temperature rise. These test may be an option for an additional adder wshoud the customer want to vrarify the design with a factory test.
That stuff was fun to sell.

 

[SG-1]

I'm just going by the Westinghouse gear that I sold, both MV and LV the old DHP one of the original VCP, then the VCPW, DS, Magnum DS, etc. I have taken my customers on factory tours and have never seen fans used to cool bus in either indoor/outdoor, or walk in electrocenters. Yesthe original design must be tested to assure that it complies with temperature rise. These test may be an option for an additional adder wshoud the customer want to vrarify the design with a factory test.
That stuff was fun to sell.

The reason you have never seen the fans is because they are hidden behind the 3000A ventalation intake screen. You would have to press your face up against it and look up to see them.

If the OP were looking at 4000A & 3000A gear he would see the same size copper.

 

[zog]

For 480V gear there is up to 6000A ratings, I have a few here as well as hundreds of 5000A stuff.

4200A is the largest 15kV breaker I have here and it has fans on board. (I have some 6000A MV stuff but it is oddball like field discharge applications)

Typically when forced air cooling is used there will be a slash rating for frame size for with and without forced air cooling.