Switchgear versus switchboards 4

[jthjr]

This seems to be constant topic in our office. I was wondering if someone could give me their opinion of the basic differnece between the two.

Thank you.

 

[rbulsara]

Why don't you do your own research and post your undestanding here. Then folks here can comment on it. That is a better way to learn and share knowledge than just ask for a ready made answer.

There are bunch of hits when you google the topic. Also ask your local sales rep for GE, SQ D etc.

 

[asco1]

Switchboards are built to engineering guidlines set out in UL 891.

Switchgear is built to UL 1558.

 

[RonShap]

rbulsara has a good point.

The main benefit from the UL listings mentioned above is that the SWGR is 30 cycle rated and can be installed without instantaneous overcurrent protection, and assist selectivity.

 

[RRaghunath]

I thought switchboard is the one that houses switchgear, such as contactors, circuit breakers??

 

[rbulsara]

rrghunath:

It is more along the line of what ronshap indicated. Regardless of OPs indifference, I would add that in the ANSI world, switchgear is built to a higher standard (heavier duty) than a switchboard. I do not remember exact sub-para no. of ANSI but its part of ANSI 37.

Also switchgear meets UL 1558 while a switchboard meets UL 891. Main differences are in bus clearances, insulated bus vs. non-insulated. compartmentalized cubicles vs not, barriers between sections, etc .and most important of all which breakers are used. Switchgear by definition (standard they have to meet) will use air power circuit breakers having a short time withstand capability while switchboards could use insulated circuit breakers and has to have instantaneous trip function in it as the assembly is not rated for short time withstand capability.

I am sure some equipment manufactures may have better white paper on the subject.

 

[hogdawg]

I work as an EE for a switchgear company and assure you that UL891 is more stringent. Ironically though, their not interested in short circuit and coordination studies. I you claim 10 kA, you build to 10 kA. The big difference is bus bar sizing, bracing and name tags.We build most of our switchgear to ABS, USCG & IEEE45. IEEE45 is more stringent than the others except for voltage regulation. Anyway, switchgear to us is switchgear with construction and design dictated by regulatory bodies.

 

[asco1]

UL891 (Switchboards) contains defined minimum bus ampacities, bus spacing, & bus arrangements. 891 also defines minimum support & bracing requirements based upon the necessary short circuit requirements. Basically, UL891 is an engineering guideline for building safe equipment that will meet NEC requirements.

A Note: A manufacture need not adhere to the guidelines set in 891 if his gear has been tested and his methods are in his UL Listing.

UL1558 (Switchgear) contains minimal engineering guidelines. It is mostly a set of requirements that must be met by a manufacture's testing. Bus ampacities, bracing, etc... must be designed and tested. UL witnesses these tests and the design methods are placed in the manufactures UL listing. (These methods can also be placed into a manufacture's 891 listing.)

Thru testing most manufactures have been able to utilize less bus and closer spacings than required in UL891.

 

[rbulsara]

While UL 1558 and 891 comparison is interesting, there must be some other ANSI standard requirement that makes "switchgear" more robust and they are. May be someone in manufacturing can enlighten.

 

[Kiribanda]

jthjr,

Sorry for the late reply. I have not visited switchgear forum for a long time.

Always try to refer IEEE 100 for such definitions. Per IEEE 100,

Switchgear: A general term covering switching and interrupting devices and their combination with associated control, instrumentation, metering, protective and regulating devices with associated interconnections, accessories and supporting structures used primarily in connection with the generation, transmission, distribution and conversion of electric power.

Switchboard: A large single panel, frame or assembly of panels, on which are mounted, on the face or back or both, switches, overcurrent and other protective devices, buses and usually instruments.

Hope this helps.

Kiri

 

[peebee]

Don't quote me on any of this, but...

I believe switchgear has a more robust enclosure, I believe it is designed to withstand it's stated fault current with no deformation. In contrast, I believe switchboards are permitted to deform, so long as they don't rupture.

Due to the instantaneous trip issue mentioned above by RonShap, I don't believe you will ever find an insulated case breaker in switchgear (although the power breakers are looking more & more like the insulated case breakers every year). Switchgear will only contain ANSI-rated air-power breakers. Those insulated case breakers always include an integral instantaneous trip, even if there's no evidence of it on the outside, they need it to protect themselves.

Switchboards are essentially the same thing as panelboards, just floor mounted (that may be an oversimplification, but not by much) and available at higher bus ratings than the 1200-amp maximum panel size.

 

[rbulsara]

A more authentic write up..

http://www.geindustrial.com/Newsletter/ind_nov01_left3.pdf#search='switchgear and switchboards'

 

[rbulsara]

One more:

http://www.geindustrial.com/Newsletter/ind_nov01_left2.pdf#search='switchgear and switchboards'

 

[alehman]

Switchgear, in addition to UL 1558, must comply with ANSI C37.20.1 and 37.51.

 

[Edw1n]

Swithboard is a term I use for low voltage applications
Switchgear is the term I use for Medium to High Voltage.

 

[rbulsara]

Switchgear could be either low or high voltage. Differences are adequately spelled out above.

 

[peebee]

Regarding my previous statement: "I believe switchgear has a more robust enclosure, I believe it is designed to withstand it's stated fault current with no deformation. In contrast, I believe switchboards are permitted to deform, so long as they don't rupture."

I'm second-guessing myself now. I may have been thinking of the difference between metal-enclosed and metal-clad.

Any thoughts?

 

[JBUDA54]

PEEBEE,

I think you were right. I have read the literature from the geindustrial website and it states that the failure rate in switchgear is less than in switchboard. It states that molded case breakers are reaching a market for cheap and dirty whereas the steel framed switchgear was reaching for continuity and reliability of service. The Deeper look into Switchgear and Switchboards article was the one that best explains these two design approaches.

http://www.geindustrial.com/publibrary/checkout/38652.30055.9322.47527/generic/ind_nov01_left2.pdf