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 Post subject: Arc pro calculationPosted: Sun Oct 07, 2018 11:35 pm

Joined: Wed Nov 01, 2017 6:09 am
Posts: 29
Hello, I am new in Arcpro and need some guiding. I am only using the software to test the possible to simulate the clothing and safe distance when being close to a 130 kV circuit breaker. This is large outdoor breaker. The link shows a picture of a similar breaker:
Since the system I am calculating on is 130kV and isolated star point. I figure that the voltage for a Arc then has to be between the phases and not to ground?
Voltage:Unfortunately, the software does not accept 132000V, but if I use 120 000V that is max it doesnât get all to wrong?
Arc gap:For arc gap I guess I must use the distance between the phases (not to earth?). That would be 130 cm(52 inch). Max in the software is 50 inch. So then I have to use that.
Working distance: The working distance is 240 cm(100 inch).
Arcing current=short circuit current=5kA
Duration: 100ms(6cycles in 60Hz system, this is 50Hz but I guess it would be the same in seconds)
Arc type: Three phase AC open. I think open would be correct for this kind of breaker
The calculation gives AFB at 54 inch(137cm) and a energy at 0.375 cal/cm2 at working distance.
A excel based calculator based on IEEE1584 gives a value of 5.2 cal/cm2 at working distance and 1.2 cal/cm2 at 5.3m.
The arc pro values seems fairly low, are they realistic? Would the arc in real situation not be between phases but develop to ground also(even in isolated neutral system)?

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 Post subject: Re: Arc pro calculationPosted: Mon Oct 08, 2018 6:08 am
 Plasma Level

Joined: Wed May 07, 2008 5:00 pm
Posts: 873
Location: Rutland, VT
Hello,

Voltage between phases would be suitable in your situation as this would be a phase to phase fault.
The voltage asked for in the ArcPro program is only used as a verification that the voltage can support a arcing fault. See the manual that comes with ArcPro.
You would have to use the max for distance as you are outside the range of the program.
Three phase open as it is an open air fault not enclosed in switchgear for example. See the manual that comes with ArcPro.
The IEEE 1584 model equations are only valid up to 15kV so you are way outside the model parameters so any result would not be valid.
The ArcPro values seem realistic for your parameters.

_________________
Barry Donovan, P.E.
www.workplacesafetysolutions.com

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 Post subject: Re: Arc pro calculationPosted: Mon Oct 08, 2018 10:51 am
 Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 596
Is this ArcPro 3.0? The manual states the Arc Gap has no upper limit, with a 400" maximum distance to arc.

You speak of "being close." Just being close is not generally considered to be hazard without some sort of interaction with the live circuit occurring.

Capacitive coupling ensures there will be a ground potential even when the source is un-grounded. I would suggest using the three-phase option in 3.0

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 Post subject: Re: Arc pro calculationPosted: Thu Mar 21, 2019 9:20 am

Joined: Mon Dec 10, 2018 10:33 am
Posts: 3
Check grounding. I think that this is your problem.

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atompark.com/bulk-email-service

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 Post subject: Re: Arc pro calculationPosted: Thu Mar 21, 2019 5:03 pm
 Sparks Level

Joined: Wed Jun 10, 2009 5:00 pm
Posts: 267
Location: Toronto
Jensaugust12 wrote:
Hello, I am new in Arcpro and need some guiding. I am only using the software to test the possible to simulate the clothing and safe distance when being close to a 130 kV circuit breaker. This is large outdoor breaker. The link shows a picture of a similar breaker:
Since the system I am calculating on is 130kV and isolated star point. I figure that the voltage for a Arc then has to be between the phases and not to ground?
Voltage:Unfortunately, the software does not accept 132000V, but if I use 120 000V that is max it doesnât get all to wrong?
Arc gap:For arc gap I guess I must use the distance between the phases (not to earth?). That would be 130 cm(52 inch). Max in the software is 50 inch. So then I have to use that.
Working distance: The working distance is 240 cm(100 inch).
Arcing current=short circuit current=5kA
Duration: 100ms(6cycles in 60Hz system, this is 50Hz but I guess it would be the same in seconds)
Arc type: Three phase AC open. I think open would be correct for this kind of breaker
The calculation gives AFB at 54 inch(137cm) and a energy at 0.375 cal/cm2 at working distance.
A excel based calculator based on IEEE1584 gives a value of 5.2 cal/cm2 at working distance and 1.2 cal/cm2 at 5.3m.
The arc pro values seems fairly low, are they realistic? Would the arc in real situation not be between phases but develop to ground also(even in isolated neutral system)?

How come arcing current is equal to short circuit current? In such case scenario you would have zero voltage drop across the gap and zero power release. Doesn't ArcPro calculate arcing current based on setup parameters?

_________________
Michael Furtak, C.E.T.

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 Post subject: Re: Arc pro calculationPosted: Sun Mar 24, 2019 8:43 am
 Plasma Level

Joined: Tue Oct 26, 2010 9:08 am
Posts: 2173
Location: North Carolina
Jensaugust12 wrote:
Hello, I am new in Arcpro and need some guiding. I am only using the software to test the possible to simulate the clothing and safe distance when being close to a 130 kV circuit breaker. This is large outdoor breaker. The link shows a picture of a similar breaker:
Since the system I am calculating on is 130kV and isolated star point. I figure that the voltage for a Arc then has to be between the phases and not to ground?
Voltage:Unfortunately, the software does not accept 132000V, but if I use 120 000V that is max it doesnât get all to wrong?
Arc gap:For arc gap I guess I must use the distance between the phases (not to earth?). That would be 130 cm(52 inch). Max in the software is 50 inch. So then I have to use that.
Working distance: The working distance is 240 cm(100 inch).
Arcing current=short circuit current=5kA
Duration: 100ms(6cycles in 60Hz system, this is 50Hz but I guess it would be the same in seconds)
Arc type: Three phase AC open. I think open would be correct for this kind of breaker
The calculation gives AFB at 54 inch(137cm) and a energy at 0.375 cal/cm2 at working distance.
A excel based calculator based on IEEE1584 gives a value of 5.2 cal/cm2 at working distance and 1.2 cal/cm2 at 5.3m.
The arc pro values seems fairly low, are they realistic? Would the arc in real situation not be between phases but develop to ground also(even in isolated neutral system)?

How come arcing current is equal to short circuit current? In such case scenario you would have zero voltage drop across the gap and zero power release. Doesn't ArcPro calculate arcing current based on setup parameters?

What are you talking about? Above 1 kV even IEEE 1584 assumes short circuit and arcing current are identical. The Purple book uses 89% for low voltage. The latest 1584 model uses a value between 50 and 100%. Only Lee (maximum power transfer) assumes 50%. Theoretically you are correct but for model purposes the lower current is accounted for implicitly elsewhere.

IEEE empirical equation is invalid above 15 kV but not the theoretical (Lee) calculation. However Lee assumes incident energy is linear with voltage when in reality they are only loosely coupled. It is reasonably close in some cases under 600 V. At 15 kV it is off by at least 300% and continues to increase with voltage. So if we scale it linearly to try to remove some of the gross error the value would be around 0.2 cal/cm2.

What you are doing though is the OSHA Goldilocks theory. They compared the Duke, ArcPro, and Lee results. They ranked them as âtoo coldâ, âtoo hotâ, and âjust rightâ and declared ArcPro the winner. Itâd not scientific but itâs what we have. There is no public test data at 130 kV. Iâm sure if you donate about \$300,000 to EPRI they will happily test it for you and give you a result. If you could please run 230 kV too as that is as common as 115 kV.

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 Post subject: Re: Arc pro calculationPosted: Sun Mar 24, 2019 9:24 am
 Sparks Level

Joined: Wed Jun 10, 2009 5:00 pm
Posts: 267
Location: Toronto
PaulEngr wrote:
How come arcing current is equal to short circuit current? In such case scenario you would have zero voltage drop across the gap and zero power release. Doesn't ArcPro calculate arcing current based on setup parameters?

What are you talking about? Above 1 kV even IEEE 1584 assumes short circuit and arcing current are identical. The Purple book uses 89% for low voltage. The latest 1584 model uses a value between 50 and 100%. Only Lee (maximum power transfer) assumes 50%. Theoretically you are correct but for model purposes the lower current is accounted for implicitly elsewhere..

With all due respect, I"m afraid you are wrong about IEEE 1584 as it does not really assume short circuit and arcing current are identical above 1 kV. In fact, it calculates the arcing current values as a function of system parameters system voltage, electrode configuration, gap between conductors etc). My point is that if the calcs are based on such (unjustified) assumptions than I can't have much trust the model it is based on.

_________________
Michael Furtak, C.E.T.

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 Post subject: Re: Arc pro calculationPosted: Mon Mar 25, 2019 9:22 am
 Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 596
The NESC and OSHA tables were generated with Isc=Iarc.

I'm not sure I like the idea of mixing methods, such as IEEE for Iarc and ArcPro for IE.

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