Hi,
I am wondering if anyone can give me advice on when to use double netural cables for building services: eg...data centres (with harmonics) is the only one I am thinking about.
To take it to the next step...what is the deciding factor of using double netural cable and how you can calculate...
Hi,
I looked at a few circuit breaker catalogs and I want to verify what the catalogs are saying:
For a 630A circuit breaker at 11kV network, the Ip or Imax is 50kA. Is this value the rms value or the peak value?
Thanks
Hi,
I am performing fault analysis to rate protective equipment in one of our stations. Is it necessary to find the minimum fault current?
My point is, isnt true that you only want to know the maximum fault current so your protective equipment can be rated above this level. So how does...
Hi,
I am performing fault analysis using SKM. Books often associate fault methods by finding thenevin equivalent and then using ohms law to find the fault current. And thats what i have been doing. Are the results then steady state values.
If so, how would transient analysis come into fault...
Hi given,
impedance for a 12.5kV generator
z1 = 0.0016 + j0.15
z2 = 0 + j0.18
20 = 0 + 0.1
obviously there is a x/r ratio for z1, but how about z2 and zo. I am using SKM power tools to represent this generator. And it ask for x/r ratio for all impedances?
Thanks
Hi,
Should the fault results be the same if i use these two methods:
1. bus admittance matrix
2. hand calc by using Thevenin equivalent sequence circuits
Thanks
Hi,
If the manufacture only provides positive sequence impedance for a 3 winding core type, 12/11/0.415kV transformer with out giving the zero sequence impedance, what approximation can I take?
Any links or doc that I can refer to will be very much appreciated.
Thanks
Hi,
I have performed fault anaylsis using SKM, the results obtained is quite interesting...
The biggest initial symmetrical current is LLG 19.5kA followed closely by SLG 19.36kA
However the highest asymmetrical current is SLG 47.5kA and 46.6kA for LLG fault. Why is this reverse?
Dont know...
Hi,
I have just obtained some fault currents result from using SKM, it shows that both the SLG and LL(phase to phase) is much higher than the 3ph fault.
With SLG fault I can figure out that it is possible (due to low sequence impedance) but why is the phase to phase fault bigger than the 3ph...
Hi all,
If a fault occurs in the low voltage system, and if the LV circuit breakers operate at around 8th cycle (rough estimate), what happens before the 8th cycle...will the circuit breaker blow up?
Why shouldnt low voltage circuit breakers operate in earlier cycles...2 or 3cycle or even...
Hi,
Please contribute to the advantages and disadvantages of the following short circuit methods:
1. Hand calculations: in particular methods of symmetrical components
2. Skm software
Thanks
I've entered a group of synchronous motors in SKM and tries to compare the fault currents at the buses when load (around 22kW) is at 60% compared to 100%.
The results I obtained is the same, is that normal. I believe not!!
I have done a fault analysis on a power station, and obtained results from a software. The report shows initial symmetrical currents, asymmetrical currents and initial symmetrical netural currents.
The asymmetrical currents are a lot bigger than the initial symmetrical currents. Is this normal...
Hi All,
I am working on 3 winding transformers. At present I have the primary-secondary, pri-tertiary, and sec-teritary positive impedance from the manufacture. But they dont provide any zero sequence impedances. Can anyone help?
The 3 winding transformer arrangment is DDyn11.
Thanks
I have got a problem with fault study relating to 3 winding transformers:
For my simulation, a 415v bus connected to the tertiary winding is being supplied by 11kV supply as secondary winding, and a 12.5kV generator as the primary winding. For most cases, the 415V bus gets its voltages from...
