Definition of "Visible Break"?

[dpc]

For the utility engineers in the group, I'd be interested to learn if your company considers a 480V (or 600V) disconnect switch ("safety switch") as a visible break switch for purposes of isolating distributed generation resources from your system and meeting the requirements of IEEE 1547?

Thanks,

dpc

David Castor

http://www.cvoes.com

 

[stevenal]

As long as it can be opened to verify the blades are open and then locked in that position.

 

[cuky2000]

Safety/disconnect switch rated under 600 V is considered acceptable as visible isolation device if readily accessible and lockable.
<sub>NOTE: Excerpt from IEEE Std 1547.2, IEEE Std C2, OSHA & NEC:
"There has been an evolution from the term visible-break"

• For voltage applications above 600 V “visible break” is still often used to indicate an isolating means with adequate visible inspection of all contacts in the open position. However, draw-out circuit breakers are generally acceptable as complying with the visible-break criteria.

• NEC: “isolating means” = “clearly indicating” has basically replaced “visible break.”


• NESC: Rules 173C, visible break requirement for circuit energized above 25 kV could be worked as de-energized without grounding the circuit.</sub>

 

[stevenal]

Cuky,

Your device will not make the cut here. Might pass the city or county inspection, but that's not of much use if the utility refuses to connect. 1547 leaves this part to the utility. "Clearly indicating" may simply refer to the handle position. Of course handle position means nothing if the linkage to one or more of the poles is broken inside. And the voltage limitation makes little sense since the service transformer will step up your sub-600 V to distribution levels.

Thanks for bringing "accessible" up. I neglected to mention that part.

 

[dpc]

But if it has to be opened to verify blades are actually opened, this probably requires appropriate PPE to open the cover?



David Castor

http://www.cvoes.com

 

[stevenal]

Agreed.