- Reaction score
- 1,173
You cannot use 400V as you would never get this to ground. Only short a short circuit between phases.
^ Just ohms law isn't it
Discuss Back in the 2391 days in the Industrial Electricians' Talk area at ElectriciansForums.net
^ Just ohms law isn't it
0.287 ohms
The lecturer who showed my group the question said it was likely it was designed to mislead (or a 'trick question')
This is the answer I came up with (back in the day) - unfortunately not correct
With respect your teacher was a c u next Tuesday.
I have many arguments on site today about root 3, and doubling.
All current books will use root 3.
I would have went with 800, and came up with 0.29
On my 2391 we were told to double the highest SP PSSC to derive the TP PSSC
As this is a TNC-S supply the SP PFC will be the same as the PEFC (without the bonding)
But the question is not clear, the PSSC measurement issues aside (technically root 3), the PEFC would be taken with all bonding connected too.
Q20: For a TNC-S system, supplied at 230V, 50 Ha, state
a) why PSCC and PEFC are the same (1 mark)
b) the value of PFC if Ze was 0.01 (1 mark)
c) the approximate value of PFC between phases if the single-phase value
was 10 000A.
(1 mark)
A20: PSCC and PEFC
a. PSCC and PEFC are the same because the neutral and earth conductors are
combined up to the service head where the measurement is taken.
b. If Ze = 0.01, then using the formula
a
oc
s I
U
Z = where Uoc is taken as 240V for a
nominal 230V supply voltage (Uo), then PFC 24kA
0.01
= 240 =
c. If single-phase PFC is 10kA, an approximate value for PFC between phases is
found by doubling this value to 20kA.
Reply to Back in the 2391 days in the Industrial Electricians' Talk area at ElectriciansForums.net
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