Arc Flash Analysis Practices in the UK

[tricard]

Hello everyone,

I presently do power system studies in Canada and recently received a request from a client to quote a potential job in the United Kingdom, specifically an arc flash study. I was wondering if someone could point me in the direction to the calculation standards and typical practices for performing arc flash studies presently used in the UK. I only know of IEEE 1584 as a calculation reference for industrial systems and (of course) NFPA 70E and CSA Z462 for worker protection. Have these same standards been harmonized in the UK or is it a whole different set of standards and rules?

Any help would be appreciated!

 

[ScottyUK]

We're using the US standards for now, because we have none of our own. Should be familiar territory for you.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[tricard]

Thanks for the info ScottyUK (I had a feeling you may be the one who would have the answer . One other question (again, being that I have never done any work in the UK): Determining the bolted fault current in the IEEE 1584 standard uses ANSI short circuit calculations. Do you use IEC Short Circuit calculation standards to determine the bolted fault current or the ANSI methods?

Thanks again for the help

 

[ScottyUK]

Well, they're IEC electrons...

Joking aside, most of our analyses are done using PowerTools by one of our consultants. It's an interesting question - I will have to find out. Is there much difference in the results returned by ANSI S/C calcs and IEC ones?


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[tricard]

Lol

I personally have never applied IEC Standard 60909 calculations in any of my studies. The only reference I am going off of is Conrad St. Pierre's A Practical Guide to Short Circuit Calculations, where in chapter 10 through 12 IEC Short circuit calculations are described in some detail. I will have to take a look at one of my modeled systems and see if there is any appreciable difference in fault currents.

 

[exciting]

Bolted fault calculation in IEEE 1584 actually doesn't specify ANSI. Powertools for example uses its 'comprehensive' method which is just solving a complex impedance network (and you can't force Powertools to use ANSI or IEC results).

I don't know ANSI too well, but I know IEC 909's calculations are often quite conservative compared to the 'comprehensive' ones. This is no problem for equipment evaluation, but obviously is for arc flash hazard levels. I wouldn't use IEC results as they are likely too high, although you can use the modeling data from a study.

In general the trouble with arc flash hazard in Europe is not the arc flash hazard calculations (as said, electrons are quite the same) but what you do with them. As long as there's no standards or regulation this is difficult, as NFPA 70E in some cases doesn't translate too well into 'European'.

 

[rbulsara]

For what it is worth, my software (ETAP) have both ANSI-Arc flash and IEC-Arc Flash. Haven't had an opportunity to look into the differences.

Since you would need to use a software package at any rate, it would make sense to buy the IEC option too. I also beleive that in the end it should not and would not make much difference in the resulting HRC category whether you use IEC or ANSI method. It may be worth while asking your client as to what would be acceptable.



Rafiq Bulsara

http://www.srengineersct.com