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Hi everyone, I’m setting up protection for a 13.8 kV to 400 V transformer and wondering how much inrush current should influence secondary-side protection. I know primary protection (relays, fuses) is typically set to tolerate inrush, but what about MCCBs or relays on the 400 V side? At the...

I’m modeling a system with an Eaton IZMX-16 (1600A) circuit breaker equipped with a PXR25 trip unit, and I need to configure the overcurrent protection to 350A. However, the lowest setting I can achieve is 640A, based on the PXR25 trip unit’s minimum multiplier (Ir x 0.4). Is there a...

I'm conducting an arc flash study and encountered an issue when testing a bus failure at 0.4kV (MC-002). The protective device immediately upstream of the bus does not open; instead, the device farther upstream does. In the attached case, and according to the TCC, I would expect the breaker that...

Hello! I'm trying to coordinate ground fault protections for several low voltage motors (2, 5 and 11 kW) that are protected by a C441 Motor Insight (Eaton). About the pickup current, I'm considering 3% of Full Load Current of the motor but for the instantaneous region I'm having trouble as the...

I work in the mining industry and we use a table that has load, operating and demand factors for every type of load (conveyors, fans, crushers, compressors, blowers, hoists, etc). However, I want to validate these values with a book or any reference.

This is a 230/400 V diesel generator (QAS 100 - 100 kVA). Which standard specify a ground grid resistance value of reference for this kind of installation (isolated)? I was reading IEEE 142 and 4.1.3 "Recommended acceptable values" specify: "Resistances in the 1 ohm and 5 ohm range are...

I've been told that a single lightning protection (franklin type) mast covers around 250 meters (800 ft). The total area under study is between 200 and 300 m2. Under which standard are these masts covered? Thanks!

I only have 2 years of experience doing engineering and now I am in the construction area as an electrical supervisor. The project is really simple, just 2 pole transformers (100 kVA each) and an optical fibre tie-in, of course with a few electrical and instrumentation panels. The thing is that...

I'm trying to model these systems in ETAP but I don't know how to. These systems consist in a rectifier to energize DC overhead lines that will feed the truck's wheels through an inverter and a induction machine. I was thinking in a lumped load with a 65%/35% ratio (motor/static load). Any...

I'm a trainee engineer and I want to learn good practices when drawing a oneline diagram for a project in my work. Do you know an online resource where I can study these diagrams that are ready to construct with? Thanks!

Is around there an open source software, excel sheet, etc to plot at least the standard curves that protection devices often utilize? I use ETAP but sometimes is time consuming to just check a TCC for an specific relay. Also I wanted to ask if it's the same to use an Extremely Inverse curve for...

I was designing a oneline diagram at work where I have substations (5) with a distance of 1 km between the first one and the next one (and so on). At tie-in I have a switchgear with the corresponding main circuit breaker, however, I have a cutout fuse upstream (2 km) of the switchgear to protect...

I'm currently working on oneline diagrams and I need to determine the current rating for the horizontal bus in motor control centers, switchgears, switchboards, etc. Which reference should I consider in order to write a voltage/current/short-circuit rating which is commercially available? For...

I've always seen a 50/5 for almost any load but recently I wanted to understand why my coworkers select that ratio. On what depends? FLA, direct starting (7 times FLA), etc... For example if a 575V motor has 190 FLA, a 50/5 would be undersized right? Any help would be great, thanks!

I'm trying to figure why ETAP gives a transformer damage curve with a huge difference under ANSI Std and IEC Std. If you have another source it would be great. Thanks!

I'm trying to assign a TCC curve for a Noja recloser in ETAP (Extremely Inverse, Very Inverse, etc). On what depends these curves? How can I be sure that I'm selecting the correct curve? Also, if you know of a reference to educate myself I'd really appreciate it. The system I'm trying to model...

I'm designing a project where the only information I have is the voltage level. Which short circuit level and X/R ratio can I safely assume in order to make a power flow and short circuit study in etap?

Sites like S&C give a link for every protection to download the respective TCC curves in an excel sheet. I want to draw in ETAP a NOJA recloser but I can't find any. PS: ETAP have a NOJA recloser model from library but I don't know why is the only recloser where I can't select a...

After entering transformer voltage level and power rating, when you click on "Typical Z & X/R" it assumes an impedance (depending on standard ANSI/IEC), but where does it come from? Is it taken from a standard? NEC?.

I'm reading Table 130.7(C)(15)(c) Personal Protective Equipment (PPE) from NFPA 70E (2018) and I can't undesrtand the difference between these two types of pants. Although I search on google they look the same to me. Also, this table has some items with (AN, AR and SR) which means: AN: As...