Rated Closed Loop Breaking Current

As a generality, any “rated” current value is based on a test point at which there is no significant damage done to the device that would cause it to cease functioning or change its function. More than that current value and it may be damaged or not perform.

Nobody cares about less than that value on large things like this...

Thank you, Sir! But, my question is why one only anticipates a current of less than or equal to the rated continuous current of the device? Why the closed loop current is not more or not less?

If it were more, then the device would have operated to disconnect it.

Sorry! The rating is given for a load break switch disconnector, which is not meant to disconnect any current beyond its rating.

..."Why the closed loop current is not more or not less?"...

If the closed loop current is more, this will burn up the breaker...so it must disconnect to protect itself, and the wiring and the equipment and the building and ultimately, you the user...If the anticipated current is less or more, you need a different breaker with a higher or lower rating...and wiring to match ...The safe operation of electrical equipment demands precision of rated components for safety...

"The rated closed-loop breaking current is the maximum closed-loop current the switch shall be capable of breaking. Separate ratings for distribution line loop breaking current and parallel power transformer breaking current may be assigned."

IEC 62271-103

Thank you for your response, sir! I too have gone through the IEC pages. I am not asking for the explanation of the terminology.

All I want to know is how it is arrived at that the rated closed loop breaking current is equal to the rated current of the switch.

And, this rating is given for a load break switch and not for a breaker.

<...how it is arrived at that the rated closed loop breaking current is equal to the rated current of the switch...>

Because they are one and the same.

Standards are written with testing protocols developed to determine that a device's performance meets that standard. When a manufacturer's switch has been tested and found to perform in accordance with that standard (as J Raef said earlier) the switch can then be labeled with the tested rating. Therefore the two terms you have asked about are now equal.

There is no guarantee that at a higher current the switch will perform safely. However over 100 years of experience has shown that at any current lower than the value the switch is rated for will also be safely broken by the switch.

Electrical codes are generally written with rules for the protection of users, equipment, and structures from harm caused by the electrical equipment in use. These codes therefore use a simple requirement that all equipment be labeled for the use intended (a few exceptions to this exist).

If the manufacturer changes materials or methods the new/revised product must be tested before it is labeled. Decades ago in the USA a major manufacturer of circuit breakers changed the internal jumper wire between a fixed terminal and the moving contact of the breaker and did not get it tested. When this change was discovered, the manufacturer had to recall ALL their circuit breakers in that very large family of products and could not sell any for a number of months until the new tests were finished. Within 2 years following this, that manufacturer was essentially bankrupt.

Before "hospital grade" receptacles were marketed, the manufacturer proposed a standard of "hospital grade" with increased strength and durability in use. The independent testing company accepted this proposed standard, and published it. This manufacturer had already done the work to make receptacles that met the standard so they were tested and listed before anyone else. Thus, when this standard was incorporated into the codes, this manufacturer had a temporary advantage in the market place.

--JMM

I think we might be looking for the definition of closed loop. I have been in this heavy power high voltage industry for 40 years and have not seen this term before, except in instrumentation.

My experience is more ANSI based than IEC, tho. Many HV switches I have seen are rated for transformer magnetizing current opening, or load break up to the rating of the switch, as opposed to attempting to open under a fault condition, where operation of the switch is interlocked to prevent the probability of an operator attempting to open an unfused switch under fault conditions

In addition to what myself and others have said:

When the switch is closed, the current flows in a completed circuit so the current flow is described as a closed loop from the source through the switch to the load and then back to the source. When the switch is opened this is the load break action and the switch must be capable of electrically and mechanically completing this opening action without damage to itself or anyone or anything in the vicinity. By damage I mean being rendered incapable of further operation or being reduced in future capability to operate again. Thus the switch is provided with various auxiliary devices to break the load current in such a way that the arc produced does not damage the load-carrying contacts nor anyone or anything in the vicinity.

--JMM