Confused as to what the earth fault loop is. I'm aware it's the path that fault current takes (Line-Earth) but how many times does fault current "loop"?
Hi all,
I have a question regarding the breaking capacity of circuit protective devices.
So, the breaking capacity rating of devices in domestic / 230v tends to be 6ka, and for commercial / 3 phase it tends to be 10ka.
Say the PFC at the origin was greater than the rating on the MCBs, and the...
hi, new to this forum and still training. During testing for prospective fault current at the point I get a bad reading, what ever that may be????, what possible situations would be causing and why? still trying to get my head round it...
thanks Adam
During a recent inspection on a 3 phase board I have some MCBs rated at 6KA
And some rated at 10 KA .
The ZE is about 0.04 to 0.05 depending on phase , form my calculations this works out to 9.95 KA ( I can only measure single phase pfc)
On a consumer unit we allow 16KA if its backed up by a...
Hi all,
quick question, hoping an easy one to answer. Just need to clarify this up in my own head.
When calculating fault current from Zs, do I take Cmin into account?
For example.
Zs is 0.54 ohms
So to find fault current I would calculate nominal voltage / Zs
So 230 / 0.54
But, should I...
My house is off-grid and supplied from an inverter. Max power output of the inverter is about 6kW (25A). Max fault current is 100A. The highest rated Type B MCB that can be tripped by this max fault current is 16A, so I cannot use MCBs with higher ratings than that. I cannot have a circuit with...
Can anyone help me clarify the formula in regulation 434.5.2, the time a conductor can withstand a fault current without sustaining damage.
t=k2 x S2 / I2
The regulation states I is the effective fault current.
Does effective fault current mean the prospective short circuit current/...
Hello all,
I’m now overthinking the - Prospective fault current test for the 2391 practical, the exam boards will be a 3 phase and a single phase board.
Do I test the three phase board and double the highest and use that for both DB’s or do I do one for 3 phase db1 and sep one for single phase db2
Hello All,
1.Star connected earthed neutral Source to Star connected earthed neutral load? Say if a L-G fault occurs between the source and load, How does the fault current gets distributed? To the source side neutral or load side neutral?
2.Star- Star Transformer. Neutral earthed on both the...
i understand what pfc is - the maximum current that flows under fault conditions until protective device is operated.... and i know the difference between the 2 types
prospective earth fault current
prospective short circuit fault current
My question is what (path) would prospective short...
I seem not to have access to the professional forums so I post this here:
I understand ohm's law and to get a current you use Volts/Resistance (V/R); so if it's Perspective Fault Current (PFC), it's V/R or Volts/Ze; and we divided by 1000 to convert to kA. Yes?
Is there a difference when...
puffy
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In "Advanced Electrical Installation Work" by Trevor Linsley, he says that an earth electrode rod that is 1m deep will typically have a resistance of between 10 and 200 ohms. Given that fault currents can supposedly, momentarily, be in the order of 1000's of amps, this makes me scratch my head...
Jodes
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Just done a calc on a 60kva generator at 240v and 415v for max fault current
got 556A at 415v and 1667A at 240v based on 15% reactance anyone care to check
I have recently had test readings as follows -
On a Fluke tester - loop test L/PE earth fault current 22.8 ohms but the loop test L/N was 0.14 ohms.
This points to poor main earth connection.
Should I report to DNO.
Have done in the past and after calling to test. They only test L/N and...
Hi All,
Having done my model for Amtech LV. I have noted that when Descriminating between two breakers the Pscc is taken at the load end of the circuit when analyazing discrimination between breakers.
Example being:-
The discrimination limit between upstream device Q1 and downstream device...
fzn10
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amtech
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Hi guys, haven't posted in a while. Working at a hospital now, we have 2 11KV transformers on site. We only run 1 at the time , the other is just used as a backup (close a bus coupler to bring it in). Being a nosy git, I asked about running both transformers at the same time. Obviously this...
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