When performing an arc flash study for a facility/service, does/should the study consider the line side of the main OCPD? I would assume the answer is yes - even if worked de-energized a verification that line is dead would be required. I assume this means the arc flash study relies upon overcurrent device clearing times from the utility - is that a value that the utility would normally provide, if asked, in addition to available short ckt info? For reference the example would be 480V service, 2000 - 3000A.
Arc Flash Study Question
- Thread starter nhee2
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mayanees
Senior Member
- Location
- Westminster, MD
- Occupation
- Electrical Engineer and Master Electrician
You are correct in your assumption that the line side AF level needs to be determined, and the Utility will provide you with their upstream ocpd information for use in that determination.
JoeStillman
Senior Member
- Location
- West Chester, PA
This raises an interesting point.
The cables on the line-side of a main disconnect have no short circuit protection and almost always present an unsafe arc-flash condition. For this reason, I no longer use MCB panels and switchboards for service entrance equipment. That main cable makes the whole board unsafe. Instead, I like to put the main CB in its own enclosure.
I would like to see the manufacturers building gear that has a main in an arc-proof section of its own.
The cables on the line-side of a main disconnect have no short circuit protection and almost always present an unsafe arc-flash condition. For this reason, I no longer use MCB panels and switchboards for service entrance equipment. That main cable makes the whole board unsafe. Instead, I like to put the main CB in its own enclosure.
I would like to see the manufacturers building gear that has a main in an arc-proof section of its own.
mayanees
Senior Member
- Location
- Westminster, MD
- Occupation
- Electrical Engineer and Master Electrician
.. agreed Joe.
The arc flash analysis provides opportunity for simple design changes to greatly improve safe operability for the electrical system. A remote main is an easy way to keep the interface panel at a reasonable arc-flash level during normal operation, and gives the opportunity to take advantage of maintenance settings.
The arc flash analysis provides opportunity for simple design changes to greatly improve safe operability for the electrical system. A remote main is an easy way to keep the interface panel at a reasonable arc-flash level during normal operation, and gives the opportunity to take advantage of maintenance settings.
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