Discuss Very high prospective fault currents. in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

A

Achnabreck

Ze 0.02 giving a PEFC reading of 12.4kA which equates correctly; high but acceptable with fitted 100A BS 1361 supply fuse.

However, PSC reading of >50kA. Instrument (Fluke1653B) checks out ok. Any ideas?

Will be contacting supplier when I discover who the supply company is.
 
not got a transformer, but i've got a dalek
 
Megger and i'm sure other test equipment manufacturers can supply higher accuracy E Loop Testers for use in sub-stations and the like. If you don't do a lot of substation work, then use IQ'S method, ...much cheaper!!! ...lol!!!
 
Ze 0.02 giving a PEFC reading of 12.4kA which equates correctly; high but acceptable with fitted 100A BS 1361 supply fuse.

However, PSC reading of >50kA. Instrument (Fluke1653B) checks out ok. Any ideas?

Estimated fault levels.

Taken from a table in the Electrical Association Publication.

25 kA(0.23p.f) at the point of connection of the service line to the bus bars in the boards distribution substation.




Will be contacting supplier when I discover who the supply company is.


http://www.nationalgrid.com/uk/Electricity/AboutElectricity/DistributionCompanies/

Regards Chris
 
Ze 0.02 giving a PEFC reading of 12.4kA which equates correctly; high but acceptable with fitted 100A BS 1361 supply fuse.

However, PSC reading of >50kA. Instrument (Fluke1653B) checks out ok. Any ideas?

Will be contacting supplier when I discover who the supply company is.

Appears the answer to this problem lies within the tolerance of the meter at very low impedance values; ie: it is just not sensitive enough. This seems to be common to most popular testers (Megger, Fluke etc.). As Engineer54 said above, sub-station testers required (thanks for that). Enquiry to the distribution company ensures a maximum of 16kA at cut out.
 
Appears the answer to this problem lies within the tolerance of the meter at very low impedance values; ie: it is just not sensitive enough. This seems to be common to most popular testers (Megger, Fluke etc.). As Engineer54 said above, sub-station testers required (thanks for that). Enquiry to the distribution company ensures a maximum of 16kA at cut out.

That was exactly the reason for my guide, the standard issue Meggers and Flukes etc. are absolutely hopeless at reading down to loop impedances sub 0.10 Ohms, and when you look at the difference 0.01/0.02 Ohms can make to PFC values, it is a problem.

After applying the procedure, in almost every case I've come across (probably >30) the Ze values have reduced by 0.01-0.05 Ohms, enough to make a massive difference to PFC.
 

Reply to Very high prospective fault currents. in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock