Protection Definition and 136 Threads

I just seen the Spiderman 2 movie and *SPOILER ALERT!* Gwen tells Peter to magnetize his webshooters so they won't be damaged by electro's lightning, since his webs seems to conduct electricity. Now, the explanation is that a magnetized object can hold electric charges. How is that...

Hello here, I am an Electrical Engineer. I am to be a Protection Engineer in a plant. Should I choose to be in the Generation Department or in the Transmission and Distribution Department? And between Maintenance and Operations which unit should I be, to be more operational? Thanks in advance...

Hi just wondering does differential protection protect against turn to turn faults? Does it protect against all phase to phase faults or is there special circumstances where it won't protect the transformer?

Would Kevlar work in protecting a rear mounted auto fuel tank from being penetrated during a rear impact (such a covering a Jeep Grand Cherokee Fuel Tank with Kevlar fabric or Kevlar Sheet)? How about protecting the floor pan mounted Lithium Ion Batteries in a Telsa S Sedan (I would need about...

Li-ion cells come with undervoltage protection circuits - little integrated thingies that open up the circuit when the voltage across the cell drops below 2.7V or so. What sort of a switch is that? I've been thinking, if a cell is inside a large series pack - a dozen of cells for a hobbyist...

Every time I see news of a bird killing a jet engine I immediately wonder why some sort of screen cannot be placed over its inlet to either catch the bird or at least dice it into small pieces. Why is this not possible?

Hi there! I'm a third-grade physics student and I'm trying to understand the physics of topological insulators, I have found this thread, where somebody else has already asked this question, but in that thread it wasn't really answered in details, they concentrated on other issues. My...

I know biased differential protection system. But one differential relay I have at work here has a feature called "Differential instantaneous highset overcurrent protection". Does anyone knows anything about it?

Hi, I have a PS&P assignment where we are designing the protection for a substation - its an overview of the type of protection etc. I have a star delta 42MVA (cyclic rating) 132:22 kv TX... I've done some research and want to use an SEL487E relay. Since this is star delta (star...

Hello, I'm a technical translator from Germany and urgently looking for a particular term: It describes a kind of case/protection around the gearbox which reduces noise emission. The German term is "Getriebekapselung" ("getriebe" = gear, kapselung = "protection/case/capsule?" Is...

EE is not my forte. Although this little circuit is so simple that I could get myself 90 percent there, it performs such an important function that I would like to get it more like 99 percent correct. I want to add the circuit to this board...

About two weeks ago, I wanted to find out more about the design of lightning protection systems. In particular, I wanted to figure out what gage of wire would be necessary for linking a lightning rod to earth-ground. What I had learned is that the gage of the wire would have to be extremely...

Hi, I made a current limit protection circuit at 1A, and I would like to improve it with an overload protection. Could you give me please some ideas how to switch off the mosfet when the load current exceed 1A? Thank you

Hello All, I'm designing a circuit board that needs to run on a 12VDC supply and will need to supply a fair amount of power to drive a bunch of 12V relay coils, in addition to some electronics. Since I want to keep the voltage drop on the supply a small as possible, I thought about using a...

The main aim of turning on/off an scr is to disconnect source from load. I read in dv/dt protection of scr using snubber circuit, the scr may turn on when dV/dt is very high as the charging current i=cdV/dt will be high enough to turn on scr. So we are using a snubber circuit to divert this high...

Well, I've never started a political thread on the boards before, nor do I usually get involved in politics because of its persistently unscientific nature, but I feel this topic is of the most profound significance and thus a VERY worthy and eminent discussion. Many in the know would say that...

I am making a totem pole digital output of 1.5-23v. i was searching for a protection circuit for the output short to ground and +24v dc. please help me out by sending a diagram of the circuit if possible.

Would this work? I can't seem to find any examples in Scifinder of carbohydrates where all the -OH groups are protected with either MEM or MOM. Is there a reason why? Will this not work? I know using MEM and MOM are pretty standard for protecting alcohols, why in the case of carbohydrates...

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I am looking for the best way to prevent corrosion between two different materials while maintaining electrical contact between them. Specifically, I am wondering about carbon fiber panels placed on an aluminum base and exposed to seawater. Carbon (graphite at least) has a much higher galvanic...

How do sacrificial metals protect the less reactive metal that it protects? Some people say that it provides the iron with electrons when it starts to rust. But if it does provide electron to the iron then the magnesium block for example will become positive ions. But then how can the magnesium...

I have attached two different schematics of circuits that I thought would be capable of protecting RS232 signals. The second one (RS232_Protect_2) I feel is all I would need to protect the RS232 chip from any mayhem that may occur on the actual device side. But, someone referred me to the...

My laptop is equipped with hard drive shock protection. If I am watching a movie and the accelerometer senses a perturbation (me shaking the computer) the image is immediately frozen, but there is no interruption in the sound. Why is this the case?

can i use surge protector for EMI protection inplace of EMI filter?what the difference between them?

What is the purpose of the grounding terminal in the plugs of some electrical appliances? Is it designed to act as an arrestor for unwanted electrical charge coming from lightning, static electricity, power fluctuations, and electrical arcs, sending the excess current to a grounding wire...

just a project i have to start working on soon wanted to know if i can get any useful information about it please thanks

I'm developing a basic cable continuity tester. Essentially, the circuit drives a test vector onto the cable and reads back the output vector. The output has MOSFETs for buffers/drivers but the input is connected directly to the ICs (CPLD, in my case). My concern is ESD. Unfortunately, I have...

G'Day guys, We have been looking around and feel this would be an appropriate forum full of good knowledgeable people to ask a few challenging questions. The missus an I are about to build a house on a mountain top that is the highest peak for at least 1-2 km's (1 mile or more). Obviously...

Hi, I am student electrical engineer and I should probably know this stuff but I am trying to work out how to determine the required short circuit current rating of circuit breaker, I have seen in the Schneider Electric catalog 'determination of short-circuit current" using cable data and...

Hello. First off, I am not an electrical engineer, have no college education, just an inventive mind, and smart enough to get myself into trouble. The project: I have a automotive computer I need circuit protection for. This computer draws a maximum of 30 (dual 15 amp fuses) amps at 12 VDC on...

Why Distance( Impedance) protection is always preffered in the Transmission Lines protection? As for as Short TL is concern, Sometimes we use distance as well as differential protection, but in Medium and Long Transmission Lines only Distance protection is used .. why is it so? what's the...

Help me. I want to use diode for back E.M.F protection.Please help me to select diode which is suitable ,like short circuit recovery time is 9 nano second and ifsm should be 30-90 amp. please also send me surge suppression protection circuit or surge protection device.

so I am creating a simple electric motor and I need a circuit that will cut the power if it is stalled (since it can create a short if it is stalled, draining/damaging the batteries) - the problem is that it also creates a short for a small period of time while in regular use I would like to...

How does solar inverter differ from conventional inverters? And what are the various protection devices inside the solar inverter?

FYI - Consolidated Guidance: 10 CFR Part 20 — Standards for Protection Against Radiation (NUREG-1736) http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1736/ I expect there are lots of questions about radiation effects and radation protection. So please post questions or...

Do wooden wall or window glass give good protection from penetrating radiation such as gamma rays?

I found this question in a book about physics, but there was no explanation. Q: Why do fruit fruit growers set car tires on fire in their orchards in the clear winter mornings? I imagine te answer would be to stop frost from forming, but I don't understand how smoke or soot could do that. The...

What would be the best protection from these two at the same time? Lead alone or a mixture of something like lead and Plexiglas?

Hey, I'm trying to find a suitable diode to protect against some back EMF in my circuit, but I don't know much about them and so I'm having a really hard time finding one. If someone could look at what i need and then possibly send me a link i'd be so grateful. Requirements: back EMF = 137mV...

I would like to know if Transposition on Transmission Lines could affect the basis and the way the power system is evaluated to set up the protection for the Transmission line? as compared to the non-transposed Transmission Lines. Thanks in advance, Regards,

I am interested in determining if a method can be devised to create a safe zone for humans to be accelerated at very high G force. I watched a very interesting experiment where a water filled balloon was submerged in container of water and had 60 g's of force applied via a centrifuge. The...

An egg is hard, but yet delicate food that people have been making contests of, for many years. But i am part of one that i lack the physics to figure out the perfect device here are the simple rules of this contest. Holy Omelets Batman… It’s the Egg Drop Contest! Design a egg protection...

Hello, I am designing a motor controller, and I was curious about the MOSFETs I'm using that have an internal body diode zener for Vds protection that is common in a lot of datasheets. I am switching the coils of the inductor with these MOSFETs, and I would like to know if its unwise to...

Hi all, anybody knows why x-ray cannot penetrate into a sheet of lead paper deeply? Do only the big amount of electrons in lead atoms diffract the x-ray, or the protons in the atoms also contribute the diffraction ? Thank you for your time!

This from another thread (according to PF's rules, the quoted part belongs in that thread, but the follow-on part belongs in its own, separate thread): So: mheslep, yours is a very good reminder that market economies will render whatever new technologies at least as expensive as any...

I need to prevent a malfunctioning load from drawing too much current from a supply of around 3Vdc@2A(max). There is already a current sensor in series with the load which outputs a voltage, Vsense, proportional to the current drawn by the load. I was thinking a PMOS switch with the gate tied...

Does somebody could advice me, whether the nominal primary CT to be used for REF protection must be same? The CT I have now as follow: Power Transformer: 60MVA, 150/20kV, Ynyn(0)d1 CT on 20kV switchgear 2000/5, class 5P20 CT on neutral Power Transformer: 1200/5, class X Relay to be used...

why you are safe inside a metal car during a thunderstrom?

I am trying to protect a generator fro loss of field with a reverse KVAR relay. My question is does a reverse KVAR relay's current transformer need to be upstream or downstream of AVR's connection to line voltage? (AVR is automatic voltage regulator) Does it matter at all.

What is the difference between a reverse power relay and a reverse KVAR relay?