cadpoint
Senior Member
- Location
- Durham, NC
- Occupation
- Electrician - but not by NC Law.
arc flash study
- Thread starter anbm
- Start date
- Status
You can get remote operators, see http://www.remoterackingsolutions.com/remote-switch-operators.htm
One problem. How do you test the voltage to verify that the panel is de-energized once you have switched off the main breaker?
GE Arc Vault
GE Arc Vault
I agree with remote operators (possibly a electrically operated breaker)..The only issue with the GE ArcValut is the required ceiling height above the unit I believe it recommends a 12' ceiling minimum, also the space required if the room is already laid out... Also the solution is a passive solution meaning you have to turn it on like a energy reduction switch I suppose you could leave it on at all times if required. However it is made to work in conjunction with a transformer primary overcurrent device, so when the device engages it quenches the fault while at the same time it also trips the transformer primary overcurrent device, that in this case will not be there with a secondary service, these devices also are only rated for one incident after that the unit needs to be inspected and possibly repaired depending on the magnituide of the fault before being re-entered into service. Arc flash switches may be the way to go. Another option is to isolate the main breaker in it's own vertical section then you may be able to label the adjacent sections based on the TCC of the main and the only cubicle with a 4 or danger category will be the section with the main breaker. Final solution work on de-energized equipment...
GE Arc Vault
I agree with remote operators (possibly a electrically operated breaker)..The only issue with the GE ArcValut is the required ceiling height above the unit I believe it recommends a 12' ceiling minimum, also the space required if the room is already laid out... Also the solution is a passive solution meaning you have to turn it on like a energy reduction switch I suppose you could leave it on at all times if required. However it is made to work in conjunction with a transformer primary overcurrent device, so when the device engages it quenches the fault while at the same time it also trips the transformer primary overcurrent device, that in this case will not be there with a secondary service, these devices also are only rated for one incident after that the unit needs to be inspected and possibly repaired depending on the magnituide of the fault before being re-entered into service. Arc flash switches may be the way to go. Another option is to isolate the main breaker in it's own vertical section then you may be able to label the adjacent sections based on the TCC of the main and the only cubicle with a 4 or danger category will be the section with the main breaker. Final solution work on de-energized equipment...
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This is an important point to keep in mind when discussing most engineering controls used to limit arc flash hazard - keyed instantaneous maintenance mode switches (RELT, ARMS, etc.), zone selective interlocking, other instantaneous blocking relay schemes, differential relaying, GE arc vault and other arc quenching technologies, etc. All of these techniques require a device that can be tripped that is upstream of the area you are trying to protect. Given that we are often trying to protect a panel/switchboard/Switchgear including the bus/cable on the line side of the main, this generally requires a transformer primary breaker or the ability to trip a remote breaker at the same voltage level.
Several manufacturers have released european style plastic throwaway medium voltage breakers that have been tested to IEEE C37 (ANSI) requirements and are sold to retrofit into metal enclosed switch enclosures on the primary of transformers. I'm not a fan of throwaway, non-maintainable breakers at any voltage, but when they can be applied in a "synthetic main" configuration to increase safety I encourage their use.
Medium voltage vacuum breakers
Medium voltage vacuum breakers
The only problem with the solution if the transformer (dry type) has a medium voltage overcurrent device directly on the primary side there may be a problem with the vacuum breaker and associated chop currents and the potential for voltage transients that can occur when the vacuum interrupter in a vacuum circuit breaker opens. This can cause potentially catastrophic damage to a dry type transformer depending on length between the OCPD and the transformer and if sunbbers or not are installed.
Medium voltage vacuum breakers
The only problem with the solution if the transformer (dry type) has a medium voltage overcurrent device directly on the primary side there may be a problem with the vacuum breaker and associated chop currents and the potential for voltage transients that can occur when the vacuum interrupter in a vacuum circuit breaker opens. This can cause potentially catastrophic damage to a dry type transformer depending on length between the OCPD and the transformer and if sunbbers or not are installed.
the blur
Senior Member
- Location
- cyberspace
Rather than a remote operator, how about turning off all the breakers below the main, then flipping the main back on. Weather it's 600amps or 800amps, what ever, so there is no load on the panel at all. And no reason for the internals of the main to arc over. Then slowly load the panel by turning on 1 breaker at a time.
Would this eliminate the need for a remote operator ?
or do I need some arcflash training :happyyes:
Open Neutral
Senior Member
- Location
- Inside the Beltway
- Occupation
- Engineer
A mentor nearly died under such circumstances in the early 70's. It was an Electrocenter they were installing; they had all the starters racked out, and closed the main to bring the lights & utility outlets up.
Little did they know the busbar in the wall had slid down in shipment.
The breaker exploded, blowing the locked door open, knocking Bill onto his side, with 2nd degree burns to his arms and hands. Behind Bill, the contractor was also down.
The arcing continued, with the feeds down from the pole to the building finally burning loose, and flapping in the wind -- the arc would blow them apart [right hand rule] the arc would stop, and they'd drift together again .ZAAAP... ZAAAP...
Bill was trying to get up when the contractor ran OVER him, foot right on his back, going for the utility substation to pull the primary disconnect. Before he got there, the sub's primary fuses went "sounding like a 12 ga. going off in my ear BLAM BLAM".
He was in the hospital for 4-5 days.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
We SCUBA divers have the same joke about sharks and dive buddies. Sometimes it involves sticking your buddy with your dive knife.I ain't gotta outrun the bear, just the fella behind me.J/K my friend.
the blur
Senior Member
- Location
- cyberspace
But that was a total equipment failure. I'm talking during routine maintenance. drop all the load, and then throw the main back on, and then 1 breaker at a time after that.
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