morning

hm, I wonder why inductors you can buy so often have so large tolerances... when I self wind one it is always muchnearer to the values the tools calculated...

@PlasmaHH Maybe the meter they use during production is not as accurate as yours?

or it has to do with the fact that many inductors are sensitive for their environment?

@jippie For ferrite core inductors I have a little tool. I enter the material, size, desired inductance, and then it outputs me the windings. I do them and usually they are at most 5% off... (whatever of that is to be attributed to my meter). However when I look at datasheets of similar ones I find +-10 or even 20% tolerance...

@PlasmaHH Are you measuring your self-wound ones over temperature?

gosh

has anyone got any ideas for measuring leakage current in up to 600kV DC systems?

fast transient, microamps range

anyone with experience able to point me in the right direction?

@KyranF At my last job we had a special machine for the fast transient test. Not sure if it applied to 600 kV systems (likely not).

Since this test is AFAIK a regulatory one (EN?), I'd say you need to use a certified calibrated instrument for the test.

can some highly insulating material be used as earth instead of the actual 'earth'

@Gowtham "Ground" should be conductive, not insulating.

What kind of "earth" are you talking about? For safety? Or for an antenna? Or for a signal return path?

is Ground really conductive in the sense that it can discharge any amount of electricity ? this is my confusion

if the surface of all earth replaced by a metallic conductor and we apply a potential difference between two far points will there be a current between those points

@Gowtham The actual earth is not a great conductor, but it is a conductor. When we talk about a ground node in a circuit or power distribution system, we idealize it to be a good conductor.

@ThePhoton i think my confusion got cleared after reading wiki on Ground(Electricity)

@Gowtham Even with the not-so-great conductive ground we have, we can use it as a conductor. For example, some power systems use the actual ground as the return conductor, instead of cabling a neutral wire.

Even though soil is not a great conductor, the possible cross-sectional area is very very large.

ha ! thanks, i was actually trying to answer something back in Physics.SE and i just had few silly doubts :)

@ThePhoton well I think i'm allowed to do low-side leakage sensing. It's a safety system for detecting unsafe amounts of leakage in an aerial barehands high voltage DC system

@ThePhoton nay, the datasheets seem to all specify that range for 25°C unless things like "electrical specifications at 25°C" do not count for inductivity...

ground is like the hindenburg... dangerous when floating...

ground is a difficult concept, especially when doing isolated transformer based systems.. like, how the **** do you get a stable ground reference?

and having a microcontroller and op-amp circuitry floating up at 3kV and working fine, makes me sweat in my dreams

lol

@KyranF I'm curious how you even test leakage on the low side? Do you measure current into a load and show that it's equal to what was delivered at the source?

@ThePhoton you insert your device between all the insulated equipment and earth.

@KyranF But how does that prove there isn't a leakage path some other place than where you put your measurement equipment?

you measure all the possible channels of leakage (the various equipment stages) and they all go into the device, and out to absolute earth

because that has to be very carefully set up

you must try to ensure ALL paths are covered

it's very obvious that if you miss something, the measurements are effectively useless

there are special connectors and end-terminators for these insulated aerial booms for HVDC work

here is something that does basically what i'm going to be doing, but mine will be more custom to the client's needs voncorp.com/shop/40/BCM+Series+of+Boom+Current+Monitors.htm

@ThePhoton you do HV live work?

@KyranF No --- That is why (I guess) i've never heard of the stuff you're talking about. And also why I'm still alive.

@ThePhoton haha well, the highest voltage i've ever worked with was 24V. This is a new world to me

@KyranF Keep one hand behind your back. And remember your rubber-soled boots (with maybe 3 foot thick soles)

@ThePhoton i'm probably going to get a HV circuit designer from elsewhere to check over my stuff

@KyranF I assume you're a PE (or whatever you have wherever you are)

well i hope i wont be needing to test on the 600kV

will have to be done at one point though

@ThePhoton i'm only 2 years out of university, but my boss is a PE (canada)

@KyranF Well, if that's what you're working on I'm sure it will be a bit of a heart-in-throat experience the first time you put your own seal on something...

@ThePhoton yes, well i'm glad its just leakage detection, meaning I don't have to directly do stuff up at 600kV. Everything is on the other end of many megaohms of insulation

@KyranF I don't know which would be worse...working at 600 kV myself (and trusting that everything everybody else set up was done right)... or designing equipment for that work and sending somebody else out with his life depending on my work.

@ThePhoton well these dudes get up on a crane and "energize" their bodies up to the working voltage, and have to remain isolated from everything else. How crazy is that?!

@KyranF I've seen the video of the guy up on a line above a forrest in a metal suit...crazy stuff.

voltage levels up to a hundred times more than the usual static

@PlasmaHH Also remember that they are probably trying to set a loose spec to minimize the need for testing. Like if you order 5% resistors, they will usually all be within 1% of nominal. If they are "6-sigma" they will be setting specs at at a point where yield loss is 1 in a million. And most of the actual parts will be much closer to nominal.

@ThePhoton I understand that very well for all kinds of other devices, but for inductors it should depend mostly on number of windings (which is dead easy to control) and A_L ... unless of course A_L is hard to control, but then I must have been lucky to get A_L values very near to the specified values

sigh ... what is being taught at school these days ... sometimes I really worry about the future of engineering when I see some of the questions.

@jippie I gave up worrying. I know this planet is doomed.

"Static characteristics: [...] Dynamic Resistance" ...

hum, diacs/triacs are one of those things where I will always be slow reading the datasheet

@PlasmaHH I charge my batteries from the negative resistance of them.

@jippie Tried that once too, was too slow, batteries imploded and now I have a black hole for my keychain... wondering where all the changes goes though that I put in my pocket

hm, I never understood when questions get to the hot network question list...

agreed, some of them are pretty random. certainly not "hot"

But I won't complain about the extra rep this inevitably generates ^^

@PlasmaHH see here: What formula should be used to determine “hot” questions?

yeah if they go haywire you can get 20-30+ votes for a random question

and here: What is the Goal of “Hot Network Questions”?

@KyranF Not random random. You would get windfall upvotes when the question has general appeal.

This "Hot Network Questions" feature often doesn't do us justice, because it misrepresents EE.SE.

then maybe that general appeal isn't always easy to understand

@PlasmaHH No, it's easy to understand. Perhaps too easy. But general appeal electronics questions is not what EE.SE is about.

I think it's possible that when we see a shit question, we all click on it and start commenting/posting crude answers, which actually makes the question look "interesting" and "hot" when it's really a bad example of a good question. That's the nature of EE.SE these days, and while it's funny (for us) it looks bad from outsiders perspective. There's been a lot of discussion about this general negative attitude on the EE.SE Meta of course

This happens moreso than a genuinely good question popping up, thanks to the flood of terrible quality questions we get here daily

yeah, it seems that it drags people to the specific sites that then start asking worse questions, which get on hot, and then there are slightly worse questions that get hot too etc. in a downwards spiral..

I can see that in waves on aviation I think

But the flood of terribly bad questions isn't as bad as on SO ;)

But there it is wanted these days :/

@KyranF I wonder how many of our questions that end up on the hot list also get closed? I don't hesitate to close a hot list question when it's off-topic w.r.t. EE.SE.

if a genuinely good question is seen, it's usually answered by a person who is most qualified/experienced to answer it (because it's a risk to propose a solution sometimes)

and will thus get limited people clicking on it, at least "initially"

@NickAlexeev Watch my current question, it gets closed soon ^^

Here are some examples when the hot list system didn't do EE.SE justice.

This is a borderline off-topic question. It's okay. But not great from EE.SE perspective. Nothing to brag about across the network.

@NickAlexeev btw. while you are here... I am still confused sometimes about what questions to migrate away and which not ... e.g. electronics.stackexchange.com/questions/161376 is imho mostly a programming question...

This one ended up on the hot list because of all the comments under it. But most of the comments were non-technical meta. I have edited the question to make it more on-topic. Still, there are 3x close votes.

Well if the damn embedded systems stack exchange would hurry up and go into action, we could shift things there

I don't like how people upvote a question which shows little attempt at research/solving the problem themselves

the upvote/downvote context text says what they are meant to represent

and 2 people even "favourite"d that question Nick!

@NickAlexeev yes, editing out the repair part "rescued" it, also the first version of the question had a terribly useless photo

I love it when Olin jumps in and abuses the question poster about their camera qualities

gives me a good laugh he does

@KyranF every stack will be swamped sooner or later by people not willing to spend any effort...

yeah, olin gives ee.se some spice ;) see my meta post..

@PlasmaHH Yes, that's a softie question. But, part of the answer is: "You may or may not be able to accomplish that in software, you may need a hardware solution". It took us a week to get enough clarifications from the O.P.

@NickAlexeev something that shouldnt be necessary... putting things on hold should at least set some incentives to add useful information ;) in the question though he asks for a fix to the code... sure for many such processing adding some hardware can be a solution but I think not many people would have thought he wants something besides a fix to his code...

@KyranF what I really hate is people whining about that a downvote is not explained.

@PlasmaHH As we speak, that question is on its way to Ar.SE

@PlasmaHH I've read (and upvoted) that one.

@NickAlexeev hehe, ok. reading around on meta, it seems that there isn't much of clear guidelines on when/what to migrate... I don't want to sound rude/offensive, but.. maybe the mods should have a (chat) meeting or so? I dont care much, but I flagged that question, migration request was declined, asking another mod (you) it gets migrated... everyone is different but I see how some people may find it quite arbitrary (there was one recent meta post about that too)

being part of a C++ irc channel I really love strict topics and sending people to the right place btw...

@PlasmaHH , not everyone on EE.SE is a German or a Brit.

lulz

I think I should go to bed now, my kids didnt allow much sleep yesterday... will see you guys in 10 hours and complain about my question being closed as offtopic ;)

@PlasmaHH Good night!

I'll go back to my devices myself.

What does "electrically bonded to the system ground and a properly sized driven ground" with the context of installing an electrical measurement device?

the part i'm asking about, being "properly sized driven ground"

Could that be an Earth reference spike set up nearby? for portable test equipment working on HVDC lines

@KyranF Could you posts a link to where that line comes from?

It's in the installation and hookup section of the VON BCM44-B

voncorp.com/shop/40/BCM+Series+of+Boom+Current+Monitors.htm

manual

also it says "12 or 24 volts D.C. negative ground" in the power requirements, does that mean it needs -12 or -24VDC?

well i've come to the conclusion that it is indeed a "Driven" spike for earth reference.. There is mention of a ground fault detection circuit as well, which would use that earth reference