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 Post subject: New edition of CSA Z462
PostPosted: Fri Jan 09, 2015 1:50 pm 
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Now the Table 4C provides arc flash PPE categories for DC systems. What is that based on? When this standards will become a code in Canada?


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 Post subject: Re: New edition of CSA Z462
PostPosted: Sun Jan 11, 2015 11:54 am 
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Based on the values given in that section and the Doan equation given in the Annex. The Ammerman equation is a little "tighter" and gives values that are lower but so far the limited DC arc flash testing that has been done has shown that even the theoretical values are way off. In addition just as with AC, most real world equipment is nowhere near the values given in the tables and thus actual analysis is a better approach.

For example, testing at Kinetrics (Ontario Hydro) commissioned by Duke (largest utility in the States) found a maximum arc flash hazard at 20 kA on 130 VDC (125 VDC substation system) at the smallest spacing of right at 1.2 cal/cm^2 when it sustained for a maximum of 0.8 seconds with a 455 mm (18") working distance. One report "normalizes" this to only 12" working distance and out to 2 seconds which defies the physics of the situation and flies in the face of human ergonomics (normal "work zone" is 15", slightly declined so it ends up around 18" to the face/chest). Once the spacing is increased to the normal spacing actually used in substation battery terminals, arcing simply won't sustain and the hazard doesn't exceed the threshold. At higher voltages the arc is actually a concern, but most of the table entries would correspond to the 125 VDC substation situation or less. The theoretical predictions are 200-300% higher than the actual test data that Kinetrics measured.


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 Post subject: Re: New edition of CSA Z462
PostPosted: Wed Jan 14, 2015 9:58 am 
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Doan's method of estimating DC arc flash incident energy is based on the concept that the maximum power possible in a DC arc will occur when the arcing voltage is one half the system voltage.

Please note that maximum incident energy does not necessarily match the fault current (equal half the available bolted fault current according to Doan) producing maximum power. The IE is a product of power times time. The Doan's method does not take into account the fact that it usually takes longer for protection devices to clear fault at lower fault currents. Hence, IE will not in general reach its peak value at half the bolted fault current.

There are alternate approaches for DC arc flash analysis available. Check for example On the performance of arc flash analysis in DC power systems for more information.


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 Post subject: Re: New edition of CSA Z462
PostPosted: Fri Jan 16, 2015 3:22 pm 
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I have checked. Ammerman's method is considered the best out there and is based on an analysis of a lot of history going way back to Hertha Ayrton. DC arcs have two regions, a "high current" region where arcing voltage increases only very slowly, and a "low current" region where voltage is quite high but current drops off very quickly. Ammerman's model uses an iterative calculation to determine both arcing voltage and current using this model. But other than this change, it still applies the rest of the Lee-style calculation directly. That is, assuming that all power through the arc is converted dircetly into thermal energy.

Unfortunately the relationship between incident energy and arcing power is not a constant, as actual testing has shown. So Ammerman's model produces values that are 25-50% lower than Doan's but is still off by a factor of 50-500% compared to actual test data. This is really unfortunate because if we can nail down the DC model sufficiently then it is a simple matter to use the DC model in a time domain analysis and the results for AC would come "for free" for any arrangement (single or 3 phase).


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 Post subject: Re: New edition of CSA Z462
PostPosted: Tue Jan 20, 2015 3:28 pm 
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Any one knows how long is the transition period for the using of 12 edition and 15 edition of CSA Z462? We have project started late last year and will deliver the labels this month c/w report. It is not easy to convert everything to meet the requirement of 15 edition.


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 Post subject: Re: New edition of CSA Z462
PostPosted: Sat Jan 24, 2015 1:27 am 
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No transition period specified. 2015 is already the current edition. Don'tforget that its a voluntary standard, sort of.


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 Post subject: Re: New edition of CSA Z462
PostPosted: Thu Jan 29, 2015 5:04 am 
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Location: Calgary, Alberta, Canada
CSA Z462-12 has not been adopted into OH&S Law in any Province or Territory to date.

That said Alberta OH&S does have a proposal in place to adopt two (2) Clauses of CSA Z462-12 into OH&S Law, Part 18 PPE. This may be approved by the fall of 2015.

It will never be adopted as an independent "Code" as you are referencing CEC Part 1. If and when CSA Z462 is adopted into law it will be OH&S Law either by each individual Province or Territory or Federally.


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 Post subject: Re: New edition of CSA Z462
PostPosted: Thu Jan 29, 2015 5:08 am 
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Location: Calgary, Alberta, Canada
There is NO legal requirement to adopt practices to CSA Z462-15.

Do not PANIC train your staff based on fear based or "You must update your staff" marketing from a National Training Organization. They are not SMEs on CSA Z462 or OH&S Law.

CSA Z462 as per my last post is only a referenced industry Standard.

Follow OH&S Management Systems and have a documented PLAN to have your Electrical Safety Steering Committee review the update (you can email me and I will send you a "Differences" document and updated "Boundaries Graphic").

Continue to implement the Electrical Safety Program you have based on CSA Z462-12. Update the ESP with CSA Z472-15 content, schedule "Roll Out Training" for your updated ESP.

The changes to CSA Z462-15 are significant in the requirement for a "Risk Assessment Procedure" for an energized electrical work task. You will need time to review how to document the implementation of the RAP.


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 Post subject: Re: New edition of CSA Z462
PostPosted: Mon Aug 17, 2015 11:30 am 
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What is the difference between arc flash risk assessment and annex F (risk assessment procedure)? Is arc flash risk assessment part of arc flash study or it is an additional to select proper PPE?


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 Post subject: Re: New edition of CSA Z462
PostPosted: Wed Aug 19, 2015 6:41 pm 
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An "incident energy analysis" (typically done following IEEE 1584 or ArcPro) only gives you the hazard...how bad it gets if an arc flash occurs. This is a hazard assessment, not a risk assessment.

A risk assessment goes further and looks at the likelihood of an occurrence. The goal would be to address the hazards (really all hazards, not just arc flash) and ensure that the risk (likelihood for a given injury level such as death or first aid) is similar. That is, you don't want to give first aid cases the same approach and weight as you would with hazards that could cause a fatality.

Annex F is one of a number of general risk assessment procedures. However, it is severely defective. If you want to find out what I mean, just attempt to do one yourself. What you will find is:
1. The terms in the table are totally undefined and pretty much subjective. For instance, what is a "severe" injury? Second, what is "rare" in terms of likelihood?
2. Once the 4 factors are determined, what do you do with them? This is undefined.
3. What is an "acceptable" or comparable level of hazard? Again, undefined.

Worse still, the standard has many places where it is talking about incidents that occur once an hour or similar time frames. This is frankly totally inappropraite. The correct methodology should match the incident so this method should not be used for arc flash.

It appears from my experience that although it doesn't say where it comes from, Annex F appears to be vaguely based on either ANSI TR03 or perhaps the IEC standards because both of them are similarly vague and poorly defined, and both are also specifically intended for mechanical hazards such as being struck by moving equipment while working on or near an assembly line operation.

A much better method which is more appropriate for evaluating arc flash incidents which are comparatively rare and where the injuries are comparatively severe is the CCPS LOPA standard which is developed for the chemical industry which is concerned with relatively rare incidents that are known to kill multiple people such as a number of published accidents that end up all over the national and international news. This standard addresses all the problems with Annex F.


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 Post subject: Re: New edition of CSA Z462
PostPosted: Fri Sep 11, 2015 10:47 am 
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The section 4.3.5.1 clearly define the scope of the arc flash risk assessment, it doesn't mention anything about the likelihood of an occurrence. Most items listed are similar to what we used to do in accordance with previous standards. The only thing not very clear is the phrase of "appropriate safety-related work practices." Not sure what shall be identified/included in the study report. Anyone would like to share a sample? Much appreciated!


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