Search results for query: *

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...

Thank you guys for the valuable info. They have been really helpful. TS Liew (Electrical testing, Commissioning, Power system studies)

Hi Guys, thank you for your valuable input. Assuming negligible capacitance. If the delta network experience a solid low resistance (Zn) fault to ground. Do you recon the fault current from line to ground to be Vfault/Zn? Based on the zero seq equivalent network for delta we see that the zero...

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)

Also with regards to David's proposal of %Z(o)=0.85 %Z(+), this is for core type transformer right? As for limb type, we can safely assume %Z(o)=%Z(+)=%Z(-) if only %Z(+) is given right? TS Liew (Electrical testing, Commissioning, Power system studies)

Thank you guys for your reply, David for your take on the steady state condition of fault, Waross for your take on the transient condition of the fault. Please correct me if I am wrong and show the right path. I believe the off-set @ 2.828 time ASCC is approached at really really high X/R ratio...

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 Scottf, thanks for your sharing, Let's say a CT has a Ktf=10, what does it mean? If I were to perform a test on such a CT, How do I measure the Ktf of the CT? If the CT is good, should the Ktf be <10 or >10. Some literature define Ktd as Ktf with duty cycle, as such Ktd is derived from Ktf...

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...

Hi fellas, thank you for the posts you have put up. I now understand that with the cap bank in the network, with the L, R & C switching in and out, this would cause significant transient to the network at high frequencies depending on f=1/√LC. What if in a situation where the cap bank is already...

Thank you fellas for your valuable posts. I totally get it now. The transformer zero sequence impedance test circuit shows exactly the point you mentioned in your posts. I now understand why the (0) seq test uses a single phase current injecting into all 3 branches of the transformer, forcing...

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...

@protoslash, much thanks for the link. TS Liew (Electrical testing, Commissioning, Power system studies)

Dear protoslash, could you forward the link to the slides you posted? TS Liew (Electrical testing, Commissioning, Power system studies)

Thank you protoslash for the update. This is great. TS Liew (Electrical testing, Commissioning, Power system studies)

Hi fellows, Much thanks for your reply, both your reply immediately cracked open my understanding of the concept. Davidbeach's made the concept clear since a single fault to ground (solid earth) will carry 3 x Io, this make perfect sense to adjust the fault & line impedance to fit the zero...