The province here uses DC transmission for all the Hydro lines, also very large saving in 2 conductors instead of 3.
Another plus is very little effect to the end user from lightening strikes.

I always avoid grabbing overhead power transmission lines. AC or DC does not matter, it is all dangerous. Even just a 480 volt busbar is able to evaporate a wrench out of your hand.. That really hurt the poor fool that it happened to. I heard about it a week later. The fool survived, the wrench did not.

 

Nothing like the lovely smell of 3rd degree burns..... black tissue, down to the bone... oh, the things I've seen (and smelled)

 

Topsy was not a healthy animal. I’m fact he was dying and the zoo was looking for a way to put him out of his misery. Ironically, Edison was unaware of the incident. The zoo contracted with the Edison Company ( nothing to do with Thomas Edison.) It wasn’t even his company. The rest is urban legend.

I've seen the film. It wasn't pretty. The elephant suffered. I've watched people electrocuted, seen them after they've been hit by lightning, or thought they'd see how far out they can draw an arc with screw-driver from a wave-guide....

Human safety isn't something to guess about. If the TP wants actual answers- they should contact their local incumbent utility public office and ask if there is someone there that they can talk to about Step & Touch Voltage, or the dangers. usually, they even have demonstrations and can tell you where they will be holding the next one.

 

@MaxHeadRoom , really? Did they use ignitrons to handle that kind of power (hundreds of kw)?

According to my neighbour who covers N.A. in general setting up new power station sites.
He claims it is done solid state now, SCR's etc.

 

According to my neighbour who covers N.A. in general setting up new power station sites.
He claims it is done solid state now, SCR's etc.

Thathas always been a question of mine about DC transmission lines. How does it get converted back to 60hz AC at whatever voltage? What sort of device is used for that 348 kilovolt input section. No any semiconductor that I am aware of.
As for what the TS needs to do to have a afe shop, or a safe-enough shop, Using a GFCI device for each outlet that an item being worked on is a good start. Then have a master "kill switch" to disconnect power to both lines. After that it is knowing what one is doing.

 

The generator, the step up and the transmission with respect to the system size should be looked at separately.
The windings for three phase industrial application is one practical example of AC voltage limit which is about 700 to 750 Volts.
It is from many years of experience that we notice the enamel (the dielectric coating) on the copper wire gets hot and breaks down also bearings and brushes so that the unit needs to be sent out to be rebuilt, however some units will run for a long long time and those are not cheap. Some prefer to run them at 450 VAC and it is the longevity and endurance that is very impressive this shows advange of the larger unit and being more co-op. (serving multiple houses).

The step up conversion and the transmission of electrical power on small systems can use 700 Volts without the step up but the size is limited. These design choices are size, cost, and efficiency for small systems. It is interesting that the industrial size dynamos do much better when maintained by a qualified electrical operator in a co-op (shared) system rather than all kinds of amateurs maintaining small units let alone adding KV transmission would be a safety nightmare. The large grid left alone already works but all the power gizmos incorporated into are becoming a real challenge.
Qualifying the size makes a difference in the scope of the discussion and is no longer just a simple power grid unfortunately.

 

Thathas always been a question of mine about DC transmission lines. How does it get converted back to 60hz AC at whatever voltage? What sort of device is used for that 348 kilovolt input section.

For a more in-depth description of the process here, there is this for anyone wishing to wade through it.
https://heritage.enggeomb.ca/index.php/HVdc_Transmission

 

Then have a master "kill switch" to disconnect power to both lines.

Really? Weren't you one of those claiming that you only need to put a contractor in one side of a 240VAC line to safely shut it down? In a thread not to long ago about air conditioning compressors.

 

Really? Weren't you one of those claiming that you only need to put a contractor in one side of a 240VAC line to safely shut it down? In a thread not to long ago about air conditioning compressors.

NO, I was NOT one of those. I did ay that it has been done and may even be legal, but I did not ever say it was a good idea.
The reason for suggesting opening both sides is to provide backup in case of some unusual failure mode causing a shock.

 

The highest CRT anode voltage I have ever encountered on my HV probe was 25Kv

Going from memory, the TV was a console TV (not that it makes a difference) but it was the biggest TV you could get at the time. I was just learning electronics and messing with TV's back in the early to mid 70's when my aunt asked me to fix her green TV. Heard a hissing sound and tried to locate it by ear. Got a little too close and *BAM* right in the chin. High school shop electronics teacher told me they run at 65KV. If it wasn't that high a voltage - doesn't matter to me now - or then. It hurt. Every muscle in my face, jaw, neck hurt for a long while.

 

Going from memory, the TV was a console TV (not that it makes a difference) but it was the biggest TV you could get at the time. I was just learning electronics and messing with TV's back in the early to mid 70's when my aunt asked me to fix her green TV. Heard a hissing sound and tried to locate it by ear. Got a little too close and *BAM* right in the chin. High school shop electronics teacher told me they run at 65KV. If it wasn't that high a voltage - doesn't matter to me now - or then. It hurt. Every muscle in my face, jaw, neck hurt for a long while.

The early B&W sets with small curved CRT screens ran about 20 KV to 25 KV as I recall. Then as screens got bigger and color came along many ran above 50 KV depending on the set. Early sets used a flyback transformer driven off the horizontal oscillator with a 1B3 rectifier tube with a max PIV of about 33 KV and max plate current of 35 mA (about and I think) before voltage multipliers came along. To check the presence of HV one generally used a well plastic insulated screwdriver and drew and arc. Big, very big, mistake using a graphite pencil.

Ron

 

The early B&W sets with small curved CRT screens ran about 20 KV to 25 KV as I recall. Then as screens got bigger and color came along many ran above 50 KV depending on the set.

When I came to N.A. in the early 70's I first got a job in charge of a TV service facility.
I don't recall any colour TV's being over 25kva ? We had to set them up with a HV probe. These were up to the largest CRT screens.
The smaller B&W were 12kv to 15kv.
The most challenging to repair were the Philips, built very hi-tech.

 

When I came to N.A. in the early 70's I first got a job in charge of a TV service facility.
I don't recall any colour TV's being over 25kva ? We had to set them up with a HV probe. These were up to the largest CRT screens.
The smaller B&W were 12kv to 15kv.
The most challenging to repair were the Philips, built very hi-tech.

Thanks Max, been a long time ago. We called it the aquadag voltage and doing some reading, which I should have done in the first place, it ranged from about 18 to 25 KV which would fit with the 1B3 tube I mentioned. Thinking I need some of that brain stuff for old people I see on TV. Thanks again for the correction.

Ron

 

Thanks again for the correction.
Ron

I recall one time I had a chassis strung out on a bench with a HV extension to the CRT HV.
Leaning over the set, I received a HV zap in the 'nether' regions !
NOT funny!

 

Really? Weren't you one of those claiming that you only need to put a contractor in one side of a 240VAC line to safely shut it down? In a thread not to long ago about air conditioning compressors.

NO!!! I was complaining that the contactor was only switching off one side of the 240 volts, and that while it would certainly stop the compressor it left every bit of the wiring hot. I never said it was safe or satisfactory for anything except cost reduction.

Let me go on record as stating that switching only one side of the mains when neither side is the neutral is STUPID.!

It works and reduces the cost a bit but that by no means reduces the STUPID aspect of it!

In a service shop where work is being done on equipment that is often defective in some aspect, it is a risk reduction to have the emergency shutoff break ALL of the power feed lines to an item, as it is difficult to know in advance exactly what sort of fault may be present.
That is a quite different situation.

 

And now for a bit, we need to put the dangers of AC and electricity in general, in perspective. Certainly getting a shock can cause an injury, including death. Thus it is vital to understand what one is doing and what not to do or to touch. Mostly, the serious hurts come from the unknowing doing the wrong thing under the wrong conditions. Those who understand the situation completely are much less likely to get any shock at all.
But other areas of life are also hazardous, but most folks understand the hazard well enough to stay safe. Cars are terribly unsafe, especially when they are in motion. But most of us who drive understand that and have no problems. Most people have an adequate grasp of enough kinematics to understand that a car can not stop instantly if they step out in front of it, although some evidently believe differently.
My point being that just because something has a potential for harm does not mean that harm is unavoidable. Thus the shapeless cloud of fear that some promote so intensely is inappropriate.

 

I seen or read somewhere a person well tuned to pain can withstand extreme DC currents while relatively little AC will kill. The nature was due to the repetitive "battering ram" effect on cells as opposed to constant and adaptable force related to how a stun gun locks up muscles (but not for all individuals). Can anyone substantiate this?

 

The worst shock I received was from 230VAC mains, and I had a conductor in each hand, In my case, the effect of the shock was to throw my arms off involuntarily.

 

My worst was 120VAC 400Hz on a commercial aircraft. Was installing an instrument panel someone had switched on the circuits despite having put "Chicken Rings" on the breakers. They're snap on rings that go on the breakers. If you didn't put a chicken ring ON the breaker you weren't supposed to take it OFF. Someone didn't care. The shock I took was from my right wrist which accidentally touched a live circuit while my left hand was holding on to the frame. Set me back on my bum and left me stunned and dizzy for a few minutes.

Also experienced 24VAC 400Hz. That's pretty exciting too. Don't try it.