Obviously, an LBS does not support the protection over the costs of a CB, as it is designed to meet the requirements of IEC 60947-3 only.

So how should I understand this correctly? I need to translate this sentence to Estonian, but i find it difficult to understand. What is meant by not support protection over the cost.

As I see it, the author of that text is not a native English speaker. Below I is the full context.

Large savings are allowed with a disconnector switch used as an incomer.

Obviously, an Load Breaking Switch does not support the protection over the costs of a Circuit Breaker, as it is designed to meet the requirements of IEC 60947-3 only. For example, if the cost of a CB is approximately 1$/A, a switch should be 0.3 $/A. On a 2 MVA installation the cost saving on the entire sub switchboard amounts to several thousand dollars. At this point, this strict compliance to the standard and the operating constraints results in having a LBS disconnector as the sub switchboard incomer. This solution is optimised as far as the standard requirements, operation and costs are concerned. If we use a CB as an incomer nonetheless, there will be several consequences.

  • 1
    Understanding this is dependent on fully understanding the electrical switches (and associated jargon) being discussed. As such, it's not really a question about English language.. Feb 21, 2020 at 9:50
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    Several interpretations are possible for the quote in isolation. Consider asking the author to clarify.
    – Lawrence
    Feb 21, 2020 at 9:57
  • I know what a circuit-breaker is and does (having once converted a corded hedge-trimmer to a cordless hedge-non-trimmer), but LBS doesn't seem a widely used initialism. Though one can see it is an L B[reaking?] Switch, this is not standard everyday English usage. Feb 21, 2020 at 10:51
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    In the first sentence quoted, "support the protection over the costs of a CB" looks like a mistranslation of "provide the protection of the costlier CB". Feb 21, 2020 at 11:03
  • "An LBS" (el-be-es) makes sense. "An Load Breaking Switch" doesn't. Later it says "a LBS" which is incorrect. I think you're correct in identifying the writer as not a native speaker. As such we would be left trying to guess what they meant.
    – CJ Dennis
    Feb 22, 2020 at 3:30

1 Answer 1


Yeah, it's unlikely that the author's native language is English, and certainly not American English. And, even though I'm an electrical engineer and reasonably "up" on wiring terminology, I've rarely run across "load breaker switch". And the quoted IEC doc is inaccessible without paying a fee.

My best guess is that the LBS is a switch intended to "protect" something like a motor from overloads. Similar in concept to a "circuit breaker" it senses when current exceeds some set limit and "trips", disconnecting the circuit. However, the design is only intended to protect the "device", vs protecting the entire circuit from a wide variety of over-current scenarios. Circuit breakers have very stringent specifications, and for this reason are justifiably more expensive than LBSs. One should not let the lower cost of an LBS entice you to use one where code demands a circuit breaker.

  • Thank You kind Sir. You are The Man!
    – sergei
    Feb 21, 2020 at 14:28

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