Arc Resistant Switchgear 1

[CanEnergy]

I work in maintenance department of a manufacturing company. We intend to change the hv fuses inside an arc resistant switchgear and install a fix-mounted breaker. Can we validate that the switchgear stays as arc resistant considering the construction of the switchgear will not change?

Thanks

 

[che12345]

1. I am of the opinion it is prudent to consult the OEM for advice of your intention. Their advice should be taken seriously. Any proposals by any other manufactures (may?) compromise/void the original (type-tested ?) design. It is impossible to justified any breaker that would operate as fast and with lower I[sup]2[/sup] T by paper, i.e. without going through costly lab tests.
2. Caution. Do NOT replace the existing/original fuses by any other Class or current rating.
Che Kuan Yau (Singapore)

 

[dpc]

In my opinion, the are-resistant rating is based on the original fused switch. If this is replaced with a circuit breaker, you can no longer assume the enclosure will be arc-resistant. The rating is based on a short circuit test within the compartment. Use of a breaker in lieu of the fused switch changes the geometry significantly and makes it difficult to predict how an arcing fault would evolve and how the energy would be released. Obviously, the heavy construction of an arc-resistant enclosure should provide much better protection than standard switchgear (with the doors closed), but without testing, it's hard to quantify.

If you ask the original manufacturer, I can't imagine they would certify anything related to that enclosure after you modify it.

 

[Gr8blu]

Arc-resistant switchgear meets or exceeds the (appropriate ANSI/IEEE) standards for the (appropriate voltage) metal-enclosed switchgear. Certain UL and CSA standards also apply, depending on voltage level. As an example: low voltage gear must meet ANSI C37.20.7. Testing must be performed per the appropriate ANSI/IEEE standard for the appropriate voltage level. Typically, the testing investigates arcs initiated in all major compartments (breaker cell, bus, cable compartment, etc.).

The arc-resistant rating also has a TYPE associated with it (e.g. Type 1, 2, 2B, or 2C for low voltage gear). Each type requires different levels of safety ranging from front only (with gear closed) to all the way around, in every compartment, with doors open.

The arc resistant label on the gear also includes the short circuit and 0.5 second arc duration rating. There is usually a second label indicating the operating conditions required to maintain the rating (such as door closed, for example). Changing from a fast-acting fuse to a breaker will almost certainly void the first - and maybe the second - label ... which means the gear is no longer classed as arc-resistant.

Note that it MAY actually be arc-resistant ... but you cannot call it that without specifically testing the new configuration to the appropriate ANSI/IEEE (and UL, and CSA, etc.) standards as required.

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