Dear friends,
I am working on a project to produce a merging unit to publish sampled value for IEC 61850 protocol. I have been looking around for a suitable device like the NovTech IoT Octopus & the Analog Device AD7616 board. Is there a good SV publishing software stack +hardware that's...
Dear friends,
I am curious about the subject above. Many literature discusses the power requirement of open delta transformer power requirement in the form where the load is star connected. In this case, the load current naturally has a phase shift of 30 deg. Thus causing a power factor of...
Dear friends,
If a delta generator/network (without neutral) experience a solid line to earth fault. What will the fault current be? How can it be calculated/simulated?
TS Liew (Electrical testing, Commissioning, Power system studies)
Dear friends, I've recently come across a power transformer with a very interesting way of putting its %impedance, especially the tertiary winding. The attached nameplate does not show the tertiary winding power rating but the %Z=243.9% (tap 10) meaning the voltage has to be 2.439 P.U rated...
Dear friends,
For calculation of max fault current of 3 phase transformer. The usual method of using the % positive seq Z & the rated MVA is common. How should I calculate the max single phase to ground fault current? Say I have a 220KV/6.9KV, 70MVA, 12% zero seq Z assume +,-,0 seq Z to be the...
Hi buddies, I hope you guys can help me understand the definition of current transformer transient dimensionning factor Ktf. It has been defined as the ratio of theoretical max flux over the max instantaneous flux of the ac component. I find this definition more confusing that the term itself...
Most instances during fault analysis, I assume the transformer zero seq impedance = given positive sequence impedance in the transformer manual, but sometimes actual zero sequence impedance is quite different from the given (+) seq impedance. Hope to get some conceptual explanation as to why the...
Hi Fellas, many literature proposed to accept that the coupling coefficient of both side of the transformer to be the same. As such deriving the expression of mutual inductance M=K√L1L2. Base on the picture, what if Φ11≠Φ22 then K1≠K2 then M should be M=√K1K2L1L2 but I have not come across...
Hi buddies, I have always wondered if a large capacitor bank in a 3 phase high voltage system would contribute a DC offset to a fault near it. We have had many studies of the same for inductive circuit but have not seen any on fault of capacitive circuits.
TS Liew (Electrical testing...
Dear buddies,
I hope to get some conceptual explanation on the above matter. Why line zero seq impedance & fault zero seq impedance are often regarded as 3x of its respective positive seq impedance.
Thank you guys in advance.
TS Liew (Electrical testing, Commissioning, Power system studies)
Dear Buddies, The transformer impedance voltage is given in percentage of the total impedance. This is obtained by short circuiting the secondary and inject at the primary to get a full load current on the secondary. This is also often considered the short circuit impedance.
Q1. Which impedance...
