How to De-Energize transformer?

[Strostkovy]

Wow. Rough crowd.

In my working days we had upwards of 100 journeyman electricians in our plant and one thing that I learned from them was that if there was any doubt you checked it with a meter. A transformer with no power to it isn't a problem but one with wires going to it needs to be checked with a meter. Anything that may have capacitors or batteries must be checked. Just assuming that something is dead is a good way to die.

On that note I really wish my meter had like a 6vac output that I could touch the probes to and double check my meter functions. Assuming a zero on my meter means no voltage is equally deadly.

I once worked on an electrical panel that had a main feed, and two separate breakers that were live from the load side from two different services. I shut the whole building down and still had power at the stupid panel.

 

[thermite]

On that note I really wish my meter had like a 6vac output that I could touch the probes to and double check my meter functions.

A) Use the Ohms scale or the Diode test scale or the continuity buzzer/horn.

B) WTF are you doing with your experience still wandering about with only ONE meter?

I won't go to the field with fewer that two, usually have a scope plus three on the bench, if not two scopes.

It's just easier than playing one-probe hopalong in a multivariate environment.

Kinda like the randy mouse as took a lady giraffe as a lover.

Between shagging, teasing tit, licking ears, and french kissing, poor bastard ran himself half to death.

 

[Strostkovy]

A) Use the Ohms scale or the Diode test scale or the continuity buzzer/horn.

B) WTF are you doing with your experience still wandering about with only ONE meter?

I won't go to the field with fewer that two, usually have a scope plus three on the bench, if not two scopes.

It's just easier than playing one-probe hopalong in a multivariate environment.

Kinda like the randy mouse as took a lady giraffe as a lover.

Between shagging, teasing tit, licking ears, and french kissing, poor bastard ran himself half to death.

I do that, but far prefer to have it to the correct settings and then test it, rather than check it in continuity mode and forget. At my job it's rare I have a complete uninterrupted minute to myself.

I have several meters, but they are more for low voltage stuff. I only have one I trust on higher voltages. Can't say I typically need more than one for running or debugging circuits, and I just about never need my amp clamp for this sort of stuff.

Now if there were an (affordable) meter with the appropriate ratings that only measured AC volts and had both a test voltage source, and noncontact voltage detection, I would buy it immediately.

I just keep it simple and run the appropriate sized wire through the appropriate sized conduit into appropriate sized boxes with appropriate overcurrent protection and disconnects/outlets. If there is a short in a box I look at it and fix it. If there is a short in a run of conduit I rip all of the wire out of it and rerun it. Just not that much in depth debugging needed. The fanciest I get is measuring ground impedance on questionable conduit runs. (I've never seen anything needing repair)

 

[thermite]

I do that, but far prefer to have it to the correct settings and then test it, rather than check it in continuity mode and forget. At my job it's rare I have a complete uninterrupted minute to myself.

I have several meters, but they are more for low voltage stuff. I only have one I trust on higher voltages. Can't say I typically need more than one for running or debugging circuits, and I just about never need my amp clamp for this sort of stuff.

Now if there were an (affordable) meter with the appropriate ratings that only measured AC volts and had both a test voltage source, and noncontact voltage detection, I would buy it immediately.

I just keep it simple and run the appropriate sized wire through the appropriate sized conduit into appropriate sized boxes with appropriate overcurrent protection and disconnects/outlets. If there is a short in a box I look at it and fix it. If there is a short in a run of conduit I rip all of the wire out of it and rerun it. Just not that much in depth debugging needed. The fanciest I get is measuring ground impedance on questionable conduit runs. (I've never seen anything needing repair)

Tons of meters in the market that have both AC & DC amp-clamp, peak and hold or averaging, but also FULL DMM ranges.

Others even have mini O'scope screens.

When parachuting in - 1990's emergency calls to sort an Asian nation's truant International Gateway telco switch engine interface to our critical ancillary gear, my primo meter was the early dual-trace 50 MHz Fluke "Scopemeter" but I always had a Fluke 77 DMM, too.

DIP IC inverters have been in the market for forty years that you could use to build a very precise reference source off a small battery.

You are "in the bizness".

Find or fab what makes life easier, safer, better.

Whom else knows your daily routine - and "special" - needs as well as you do?

 

[jim rozen]

One brief word of advise: don't use inexpensive, general pupose multi-meters for testing power circuits. Use the correct wigger type testers designed for this.

Bad stuff happens when you stick an old simpson meter, accidententally set to the wrong range, across some main lugs on a panelboard. 'Nuff said.

 

[TDegenhart]

One brief word of advise: don't use inexpensive, general pupose multi-meters for testing power circuits. Use the correct wigger type testers designed for this.

Bad stuff happens when you stick an old simpson meter, accidententally set to the wrong range, across some main lugs on a panelboard. 'Nuff said.

Better yet. If you don't know what you are doing (you many think you do), DO NOT MESS WITH POWER!!! That stuff can kill.

Tom

 

[thermite]

Better yet. If you don't know what you are doing (you many think you do), DO NOT MESS WITH POWER!!! That stuff can kill.

Tom

They have their place. Jim could have at least linked to one:

DAVID HERRES: All about Wiggy - Electrical connection

FLUKE Voltage Tester, 600VAC, 600VDC - 1CWL2'|'Fluke-T'+'Pro - Grainger

Others make them, too. Cheaper is cheaper. but Ideal ain't terrible.

Not in my arsenal. Not enough need.

 

[jim rozen]

As the previous wise man said (paraphasing) 'If you don't know how to work the internet stay OUT of the panelboard.'

 

[JST]

View attachment 337315

I don't know how applicable these are still but I see them commonly used. Can't say I've seen any modern profession schematics because they don't share those anymore, but I see lots of documented personal projects, as well as my own.

Then again, resistors are jagged squiggles and logic gates all have distinct shapes and you can't tell me otherwise. Whatever standards body disagrees can f off with their "every component is a box" approach.

Agree about the box symbols.* Really old diagrams can have different symbols. The jagged line can be a coil, and so forth. Those pre-date the standards, usually.

Two of the ones you show are "grounds" that ought not to be used for an isolated portion . We can argue about the "signal ground", it "can be" an isolated portion.

One thing for sure, however, is that when one of the symbols is used, then that means ANY other line connected to one of the same symbol is being asserted to be connected to the same wire.

The signal ground (really a "common", it is not showing an "earth") can be drawn with a number, etc, so you can have signal common #1, and also #2, #3, etc, which do not have to be the same.

The chassis ground, though, that's what it is and what it is is chassis ground. For most any equipment, the chassis will be connected to the equipment grounding conductor, so it will be connected to earth ground.

I've seen those misused in ways that are pretty misleading.

If any document calls something a "ground", it had better be connected to the EGC/chassis, or a ground (earthing) rod. Anything else may be a "common", but never a "ground".

* What I REALLY hate are the "schematics" in which each portion of the circuit is a little self-contained drawing, with every "wire" just going to a symbol. While there are good reasons for doing that, there often is NO table of symbols, so you are left on your own to figure out what "ACT-3", or "VCC-4", etc really is.

 

[thermite]

If any document calls something a "ground", it had better be connected to the EGC/chassis, or a ground (earthing) rod. Anything else may be a "common", but never a "ground".

Well..... at least NOW we know why your mountain bike drags a chain behind it and has cleated Iron tractor wheels instead of rubber tires.

It was the safety lights, yah?

 

[JST]

Thermite......... Do YOU wire up 3 phase with green wire for the "stinger"?

 

[Big B]

Thermite......... Do YOU wire up 3 phase with green wire for the "stinger"?

Termite has wired a lot of different things...in his imagination. Same way he machines things.

 

[thermite]

Thermite......... Do YOU wire up 3 phase with green wire for the "stinger"?

Irrelevant... I don't actually use Delta for "distribution", J.

So I have none of corner-ground, high-leg, "lighting tap", nor "stinger" under roof, lo these many years, already. Commercial Facilities Management is.... about 25 years in the rear-view mirror. Salon Films then brand-new Digital Media Studio in Hong Kong, last project of that type I managed.

Telco doesn't count. We have our own systems for OUR wire! Globally standardized, thankfully.

I do my OWN runs to NFPA 70.

When in the USA.

There is ALWAYS more than one acceptable way, too. Just not stupidly more than one. [1], ELSE I at least colour-tape ends plus a tape band on the run every meter or so if I'm short of solid colour.

Not that I'm so anal about regulations. That was Dad!

Inspector, even when not-only, for most of 36 years, Federal. NACA Langley & Corps of Engineers. Pain in the A**S to work with, but it was good training, so I aced the course at Belvoir when my turn came, then used that in "nam, then as a Senior Technical writer - power systems, site bonding and grounding, "etc." Northrop-Page "IWCS" FPTS sites for US Army SigC.

The critical years thereafter, I had a sore-competent Director of Engineering on my staff. Telco and every inch of its infrastructure from bonding and grounding to submarine cable, terrestrial shot, or geo-sync bird. Not "newbies" I asked for and GOT "first-dibs" on any Engineer in C&W's then still Global Empire. We learned and grew. Fortune 400 stayed sweet.



Codes evolve. NFPA 70 is not "Law" until your State Legislature says so, and they may not use it ALL verbatim, and may not be up-to-date. County enforcement deals with that.

So I'm not the authority. Whatever code is current is. If in doubt or wanting to do something an Inspector might challenge? I go have a coffee with my County Head of Enforcement. Ahead of time. AND NOT the Inspector.

No surprise, over the years I've run into brother retired Corp of Engineers Officers, retired USAF Base Facilities Colonels "double dipping" here in Military District of Washington.

Our head of Plumbing enforcement? The Son of another US Army Engineer Officer!

We speak the same language. Nary a problem with advance approval of a concept.



Annnd.. it's just less work to do it "by the book", right up-front.... than to have to "play detective' many, many years later when you may be under duress, time-wise and/or funds-wise.

2CW

[1] 'By WHICH book"?

A ways after the "handover" from British Crown Colony to PRC, Hong Kong government finally agreed on standardizing wiring colour-code.

They had "many" things Grandfathered, but just two "main" legacy standards ... which happened to be diametrically opposite as to the key colours.

Resolving THAT would be a Very Good Idea, yah?

But it's still China. Cooperative society. No loss of face wanted. etc.

The solved the problem THEIR way.

Made BOTH contrarian colour-codes "official".

Go figure it at least gave better job security to credentialed electricians, rather than cross-border coolies with a cheaper quote?

Also let more foreign firms bid ... so costs stayed lower!

Cooperative.... opportunists!

 

[Froneck]

Though I don't get into wiring codes often anymore, the last I seen was that the color code was removed. What replaces it was it required a building standard developed rather than a national color code. If everything was wired the same as to color it was acceptable regardless of color used. Therefor the old code of Yellow, Orange and Brown could be used for 240VAC as long as all 240VAC in the facility was the same color. However I think Green was reserved for earth ground only!
However I think the issue was simply how to de-energize a small low voltage (low as not connected to high voltage transmission line) transformer so that it was safe to work on.

 

[thermite]

Though I don't get into wiring codes often anymore, the last I seen was that the color code was removed. What replaces it was it required a building standard developed rather than a national color code. If everything was wired the same as to color it as acceptable regardless of color used. Therefor the old code of Yellow, Orange and Brown could be used for 240VAC as long as all 240VAC in the facility was the same color. However I think Green was reserved for earth ground only!

Wouldn't exactly break your computer to look it up, would it?

I still do. Worked and wired in too many countries to NOT!

Conductor size even matters, wuddn' yah know it?

 

[Froneck]

Wouldn't exactly break your computer to look it up, would it?

I still do. Worked and wired in too many countries to NOT!

Conductor size even matters, wuddn' yah know it?

I'm lazy! Plus I'm not connecting anything so "What Me Worry" In addition I will not rely on color code! Too often it wasn't correct! Too often I found so called electricians working in companies that didn't know the difference between and Amp and a Volt! Give them a screw driver with a neon lamp in the handle and they become experts!

 

[CarbideBob]

Riddle me this.
What is the below pictured and used by the millions called.
Obviously "ground" can not be part of it's name since it checks infinite resistance to earth in it's big application.

 

[SomeoneSomewhere]

Bonding strap? :P

'Proving units' are readily available (mostly for the UK), and output a known, not particularly precise voltage for the purposes of proving that your meter is reading correctly if you don't have a suitable mains source: Proving Units | Two-Pole Voltage Tester Calibration

As for colour codes, the Chinese and Soviets both agree(d) that L2 should be green...

 

[SomeoneSomewhere]

I'm lazy! Plus I'm not connecting anything so "What Me Worry" In addition I will not rely on color code! Too often it wasn't correct! Too often I found so called electricians working in companies that didn't know the difference between and Amp and a Volt! Give them a screw driver with a neon lamp in the handle and they become experts!

If you want to see a meltdown, start an argument about kW vs kWh...

 

[Froneck]

kW or kWh??? Those guys think that changing 240VAC to 480VAC will save the company 1/2 in electrical cost because amperage is lowered 1/2!!!! Convinced management to do it in wet environment!