SKM consider the relay as well; there is no need of breakers generally. As you all here are well versed with all these things, so I asked. I am sorry if it sounded so basic.
SKM is making analysis based on the maximum arcing duration i.e. 2 secs as I haven’t included any breaker. But it makes sense to not assume it to trip seeing just the protective device arcing fault.
I am getting a maximum trip time of 2 seconds. The protective device arcing fault current is 4kA.
As I have put only relay in the upstream and no breaker is there. Can I safely assume that the upstream device will trip prior to 2 sec as the protective device arcing fault current is around 4kA...
I have been analysing the arc flash results and I could see fuse on the primary side has tripped before the breaker on the secondary side of T2 transformer. Please find reference photo. Both the buses are seeing the same bolted and arcing fault. LV breaker(C1) on transformer side(T1) is...
I have transformer of 75kVA, 480/208V and z=3.6%. I am calculating the breaker settings Ir, Isd and Ii.
My breaker is of 250A.
Based on FLA, I am setting Ir and Ii by seeing fault current. I am confused about setting Isd. How should I set my values of Isd?
Can you please give me an example of...
I have transformer of 4190(Full load kVA) and Voltage is 21500V. FLA is coming out to be around 112.5A. Phase relay is kept at a CT ratio of 200/1 and Ground relay is kept at a CT ratio of 50/1.
Should I update the FLA(Amps) here as per my transformer data for both phase and ground elements?
I ran a study and I could see my SLG current coming out to be higher than the three phase current. This is first time, I encountered such scenario running studies. Is it because of impact of impedances? Can someone please give me an explanation or an article to read to understand such scenario...
I have modelled based on load list now. I have still kept utility as an infinite source though. I don’t think it will impact my load flow studies, but short circuit studies most definitely.
I am trying to run arc flash analysis in SKM. My system is at 13.2 kV. Do I need to define voltage tolerances in EPRI method too if I am running my system at 13.2kV? What tolerance range is considered to calculate incident energy?
I have changed the tap of my transformer( negative tap) and voltage drop has reduced.
But I have one more concern, can it lead to over voltage situations?
Could you please specify some content that I could read to understand more about the curves to be used in accordance to load(as you mentioned fan requires NEMA D)? Thank you!
Are there any specific standards, that specify the allowable starting motor voltage drops, the behaviour of load torque w.r.t motor torque, behaviour of motor torque and acceleration torque and, variation of speed. I have ran studies for the first time on SKM and couldn’t find much on it.
I have a motor of 44kW rating. I am choosing a typical data in SKM for my load(fan model) and motor model for TMS studies. And I could see an error of motor torque could be smaller than the load torque. What should I do to mitigate this error? I tried using different model, but still couldn’t...
