CT1 and CT4 are enough for differential protection if zero sequence currents are filtered out (CT4 should be included).
Excerpt from Siemens 7UT6 relay (similar in 7UT8): "The disadvantage of elimination of the zero sequence current is that the protection becomes less sensitive (factor 2/3...
I agree that as an author I can use any notation I prefer, as long it is consistent, mathematically correct, does not deviate too much from standards (such as ISO, IEC) and so on. However, knowing the reason behind “k” could help me select more appropriate subscript in my language (in this case...
I do not find subscript “k” in the books of C.P.Steinmetz (Theory and calculation of alternating current phenomena, 1900), W.W.Lewis (Transmission line engineering, 1928), C.F.Wagner & R.D.Evans (Symmetrical components, 1933), E.Clarke (Circuit analysis of AC power systems, 1943), P.M.Anderson...
Does anyone know the meaning of index “k” in many of the short-circuit related parameters, for example, Ik (short-circuit current), Uk (short-circuit voltage), Sk (short-circuit power)?
This index is used many books and standards in many languages. I suspect it comes from German “kurzschluss”...
I'd like to ask if anyone knows how to form an equation shown in the attached figure (from US4559491 patent).
In the image there is an expression for a phase R current at a point A for a phase-to-phase fault:
IR = (a^2 * I1R + a * I2R + a^2 * Ipre-fault) * a (1)
I can't figure out why (1) is...
I would call this a rather complicated underground system. There is no open source software for such task. You could find a freeware FEM (finite element method) software but working with such software is very challenging.
At a first glance I would blame the settings. Would it be possible for you to show us the following settings: 4302 to 4313 (I assume it is version 4.xx relay)? Could you provide OLTC data (… kV +- … x …%)?
COMTRADE would be very useful as well (to see the voltage signal, which stage has tripped...
At 100 A you see 0.3 s. If you test the relay at 150 A, it will operate faster. With lower current the operate time will be lower. That is the reson why we talk about curve (inverse, extremely inverse and so on) in contrast with the definite time overcurrent protection (50) where the operate...
I checked the aforementioned thread before I posted my question. I am familiar with [1-5] and it is possible that equations (1) and (2) are also given in Buller’s paper [6] and his methodology is similar to the one in [4 and 5]. The problem is that the cornerstone of the Buller’s approach is...
To solve for the voltage drops (as in [4] and [5]) I need self and mutual reactances already calclated. It can be easily done using (1) and (2) and then proceed exactly as you suggested. Generally I prefer [1,2,3] where reactances are calculated with (1) and (2) and balanced current sources are...
There are different ways to estimate current imbalance. The most recent and easiest to manage is given in [1, 2, and 3]. Earlier approach from [4, 5] can also be mentioned.
All these methodologies employ simple reactance formulas (ohms per 1000 feet at 60Hz):
Xii = 0.023*(K’+ln(1/rc)) (1)
Xij =...
I just received the latest IEC 60287-1-1 standard (Amendment-1 2014-11) and the phrase "Whether dried and impregnated or not" is replaced with "Conductor insulation system" (eventually, after so many years). Now I can select Kp and Ks coefficients according to particular insulation system...
Thank you for the information from which I can see how proximity effect is significantly reduced in Milliken conductors. But I'm still not sure what does "drying and impregnation" of a conductor mean? In most textbooks authors simply state: "conductor is round, stranded, dried, and impregnated -...
Hello
IEC 60287-1-1 standard includes a table with coefficients for skin and proximity effects (ks and kp) for different conductors (round, stranded, hollow etc.). These coefficients are influenced also by the condition “Whether dried and impregnated or not”.
Can anyone help me with the...
