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Dear fellows, I thank you very much for your inputs, your different points of views as well as suggestions have been very good to us. Regards,

Hello, We already looked at the software manual, however, there is no explanation about it or suggested values. Software developer was already contacted and up to now, no response. Because of that, we are trying to get some feedback from the engineering community who surely has been involved...

One question: Is your facility based on NEC code? If it is, then, what short-circuit current are you taking into account for your calculations? The one in low voltage or the one in medium? This could be easier if you have a very clear picture of your grounding system and real needs

Hello, The issue is related to several factors affecting CT performance: a) the burden between CT terminals and relay. This means you have to know the values of leads resistance, CT resistance and relay burden. They all together should be lower than CT burden nameplate. b) CT's have to be for...

Thank you for your responses! We already have a specialized software to do this fine modelling, and our question is related to know some references in order to learn to fill the fields. For example, the software used has two possible equations: 1) k(f) = (1-a)+ a*(f/fnom)^b 2) k(f) =...

Hello, You can add something to the soild, however, you should have in mind the following: 1) Despite adding something to the soil, this will be temporal. I mean, in some time the effect of the added material will have passed and the earth resistance will be againg very high. 2) I understand...

Hello, The rct value is needed to determine the total burden that the CT will have to support. What you can do is asking the supplier (or some other CT manufacturers) to provide you the whole data of CT's design under IEC standard and they would provide: CT Ratio (the one you are taking into...

Dear fellows, Currently, we are working on a harmonics study involving medium and low voltage network. As in that network there have been some prrevious problems and some equipments were reported to be damaged, we are trying to create a very detailed model based on the available information...

Dear Colleagues, Does anybody knows if the rated shortcircuit value of the LV fuses is related to: Symmetrical, peak or what current? We are trying to understand it because the manufacturer manual says shortcircuit based on IEC 60947-2 (and we have only fuses gG, not fused circuit...

Hello fellows, I have one question related to the way impedances for 3W xfmrs are given in a text protocol. We have the following: HV-MV = 4.23% HV-LV = 2.51% MV-LV = 6.55% However, the same test protocol has some other values refered to the HV rated power: HV-MV = 6.77% HV-LV = 6.70% MV-LV...

Hello, I recommend you to read the manufacturer manul, they typically explain what to do. However, I think that at least you shold test the following: 1) CTR, inject 1 A and the reading on the relay screen should match according to CTR 2) Test all the functions you have enabled and each one...

I thank your ideas, are always helpful 7another4, I would like to give you more data in order to understand our situation. This specific project is a bit complicated and I will explain you why: 1) The largest fault current magnitude is on a low voltage transformer (at 460 V) 2) We are using...

Hello colleagues, I know that related to step and touch voltages there is no problem, because the fault current flows thorugh the "four wire" according to NEC and as it does not flow to earth there are no step and touch voltages. However, this customer wants us to determine the size of the...

Dear friends, We are involved in another grounding grid analysis for an industrial system. Now, we are trying to calculate the current division factor, which for a transmission network it seems very easy to determine following some equations. However, for an industrial network in medium...

Hello I thank your answers. My concern is related to the effect on the motors and other equipments. 11% is on the busbar but, at motor terminals it is higher, besides the starting time is around 15 s, because it is a full voltage starting (100% of nominal voltage). During these 15 s, all the...

Hello, Is there any standard or practical recommendation to limit the magnitude and duration of a voltage drop caused by a motor starting? We have done some analysis and the voltage drop is 12%, however, our customer says it is not significative if not forbiden by a standard. So we have...

Hello, In Mexico, there's an independent lab which is part of the electrical utility. This lab perform many tests (static and dynamic, as well as having installed a pair of each relay as a backup protection with only alarm-not trip- during a period of time)to each relay that may be used on the...

Dear guys, I want to say thank you for this information, we will look for them and try to go deeper inm our knowledge. By the way,mcgvr, where are you from?, because you are refferring some mexican standards. Best Regards

Dear friends, Does anybody kbow what the standard to verify fuses interrupting capabilities is? I mean, we alredy look at IEEE red book, violet book and nobody talk about low voltage fuses. For medium voltage there are some other standards but, we are not fully sure if the procedure...

Is there any more comments?!! Thank you!