Short circuit current ratings, short time thermal withstand capabilities of conductors, sizing tool скачать в хорошем качестве

Short circuit current ratings, short time thermal withstand capabilities of conductors, sizing tool

You will find short circuit thermal sizing of conductors and cables in this calculation tool. It is so flexible and you may calculate 3 different cases at one time. download excel tool and ppt file; https://drive.google.com/drive/folder... https://docs.google.com/spreadsheets/... Please visit https://www.powergrid-academy.com You will find in web site excel and one ppt files. You may press and download excel tool and power point presentation file. Also this tool includes joule integral effect for subtransient and transient case calculations. (X/R ratio or DC component effect on sizing the conducors or cables) Calculations are based on two international standards and they give same results. IEC 60364-5-54 and IEEE 80-2013 As supplementary information and an example calculation for short circuit also ; Just try to understand some ratios such as I" = Initial short circuit current, Ik"/ Ik (where Ik is the steady state short circuit current) this depends on the system fault location X/R ratios. Ik" is so simple, it depends on the impedance of fault location. Suppose that you have a transmission line having a rail conductor and which is 220 kV. There is a line to ground fault just after 50 km of the generation substation. Rail ACSR conductor has a 0,0597 ohm/km per unit resistance. 50 km will give you a total DC resistance of 0,0597* 50 =2 , 985 ohm. Nearly 3 ohm lets say. Phase to ground voltage is 220 kV / sqrt 3 = 127 017 V. Therefore in simple ohm formula 127017 V / 3 ohm = 42.3 kA. This is your Ik". Or this is your initial short circuit. Suppose that you have a 8000 MVA Short circuit power at starting point of power generation substation and after 50 km you will have a short circuit. This conductor has a short circuit power of V^2 / r = 220 kV^2 / 3 ohm = 16133 MVA. Total equivalent short circuit power at fault point (50 km after generation plant) is (16133 * 8000) / (16133 +8000) = 5438 MVA. This will give you 5348 MVA / (220 kV * sqrt 3 ) = 14 kA steady state short circuit current. Therefore Ik" / Ik is 42,3 kA / 14 kA = 3,02. This ratio may vary and even can go up to 10 as you see in the excel sheet in joule integral page. Therefore, you can easily find coefficient (n). For coefficient (m) it is so easy as well. Since K is between 1,1 and 1,95 which comes from K=1,08 + 0,98*e^(-3R/X). This can be calculated exactly. But for making it easy, IEC says as K * sqrt 2= 2,5 for 50 Hz and K* sqrt 2= 2,6 for 60 hz and IEEE K*sqrt 2 = 2,7. So, you can easly find what is exactly K if the system X/R ratio is known. If you dont know, dont worry even. This X/R just comes from power transformers grid side windings. At very close location it is around ( at the transformer terminal ) such as X/R =70, while going in transmission line as 50 km, it will reduce to X/R as less as like 5. Because X is produced only in power transformer winding (as series reactance, not shunt reactance). Therefore if you know transformer parameters as internal resistance of windings and its short circuit impedance, you can easily find X and R at transformer terminal. Later on, keep X constant ( X is J * 2 * pi * frequency of grid as ohm), just add transmission line conductor DC resistance to your rectangle to find total impedance of line and to find X/R ratio of that point. Then, easily you may say coefficient K is this.. And one more thing: Joule integral works only in substransient faults such as few cycles like 100 ms. If you calculate like second, 2 second short circuits, as it is seen from "(m+n) coefficient in square, it will not be meaningful. This can be used in generator circuit breaker Isolated bus duct calculations. Or in some specific subtransient cases. Otherwise, I put 3 different metal calculations to compare them. Sorry for long explanations. :) I just wanted you to understand the basics maybe you are already aware. For upcoming electrical generation, transmission and distribution engineering calculations and tools and educational videos, please keep an eye in this channel or www.powergrid-academy.com web site.