The application of switchgear and switchboards
One important element of good power system design is the proper selection of the distribution equipment. The choice of using either switchgear or switchboard must be based on many different criteria and the design of the power system requires thought be given to each one.
Following are insights into just a few of the differences to help in making those decisions.
Standards and testing
Switchgear and switchboard structures are built and tested to different standards:
- Switchgear to ANSI standard C37.20.1, UL standard 1558, and NEMA standard SG-5,
- Switchboards to NEMA PB-2, and UL -891.
Switchgear incorporates only low-voltage power circuit breakers (LVPCB) which conform with ANSI C37.13 , NEMA SG-3 and are listed per UL-1066, whereas switchboards may include any combination of protective devices including insulated case (ICCB), molded-case circuit breakers (MCCB) listed per UL-489, fusible switches listed per U L-508 and 977 and power circuit breakers listed to UL-106 6.
Unfused switchgear is short circuit tested at 15% power factor for a full 30 cycles, while switchboards are tested at 20% power factor for only 3 cycles .
| Title: | The Application of Switchgear and Switchboards by Jerry Milton, GE Systems Engineer |
| Format: | |
| Size: | 92 Kb |
| Pages: | 5 |
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Your article about differences between switchgear-switchboard is wrong.
On this paragraph:
“Switchgear incorporates only low-voltage power circuit breakers (LVPCB) which conform with ANSI C37.13 , NEMA SG-3 and are listed per UL-1066, whereas switchboards may include any combination of protective devices including insulated case (ICCB), molded-case circuit breakers (MCCB) listed per UL-489, fusible switches listed per U L-508 and 977 and power circuit breakers listed to UL-106 6.”
You are confusing the terms, when you write switchgear must be switchboard and vice versa.
Please fix it.
thanks for the article, in indonesia generally we assume switchgear is for medium voltage, while switchboard for low voltage
HI:Everybody:
From my understanding I think a switch gear is suppose to be the source of Main Power supply to the switchboard. While switchboards are design in mind to be means of distribution to the rest of the branches of the circuits. If I am wrong please educate me further please.
Sule Ibrahim.
Plastics.
Swbd lower costs
Power brkrs
Withstand.
Terminology continues to be confusing to the reader. I am familiar with both European and North American, and when i see Switchgear, Switchboards etc, I read in context. We cant say becasue its tested differently, its one or the other. No, it can be either, its how its configured and tested for its application that counts – not merely the title.
Being specific when writing e.g. as it applies to the North American market, with dates and references will be a helpful guide to contributors.
if you consider as a switchgear a low voltage unit, what is then medium voltage unit or what is an MCC?
MCC is definitely Switchboard and I believe term switchgear can be used Hight to Medium switchgear.
Regarding “The Application of Switchgear and Switchboards” by Jerry Milton, GE Systems Engineer. It is a good one! But, it also illustrates the need for adding dates to the articles published in E-E-P. It references NEMA SG-5 that is obsolete, and the content of the article is restriced to low-voltage systems only.
Henn Rebane, P.E.