Understanding Surge Protector Specs for the Computer Age

[kiki_danc]

I can't see centertap of far transformer. Is there a wire on it ? I see only two wires coming down from that transformer.

Thing above the red arrow should be the primary winding's low end termination and the ground wire..
Here it is at 300%
View attachment 231903

Here is the front of the far transformer. so do you think it's tap to centertap overall?

 

[kiki_danc]

Here is the front of the far transformer. so do you think it's tap to centertap overall?

View attachment 231904

Seeing the full pictures of the 2 transfomers.. is the wiring like the following?

There are only 2 wires connected to the 3 high tension wires above.. where exactly does the 3rd phase wire pass by to create 3 phase? I read it's from ground? how? And why is there a Wye? Maybe the above is not illustration of my 2 transformers.. do you know where to find illustration of wiring of my two transformers? And what does P in the right wire mean? Thanks a lot!

 

[jim hardy]

Seeing the full pictures of the 2 transfomers.. is the wiring like the following?

I can't see all the wires between the two transformers' low sides
It does appear there's a wire on centertap of the last one you posted.
but i don't see it earthed(grounded)

There are only 2 wires connected to the 3 high tension wires above.. where exactly does the 3rd phase wire pass by to create 3 phase? I read it's from ground? how? And why is there a Wye?

Label the three corners of an equilateral triangle A B and C
find its center (equidistant from each apex) and label that Neutral.
Ground neutral for this exercise, but be aware it doesn't have to be grounded.
,,,,,,,,,
Now draw a line from each apex to neutral.
You now have a vector representation of a three phase voltage system
six distinct lines representing six distinct voltages, each with a magnitude and direction.
the outside ones are Delta and the inside ones Wye...

voltage from phase A to phase B is the line connecting those two apexes
and voltage from phase A to Neutral is the line from A to Neutral
We usually designate them V_from-to eg V_NA would be From N to A,
and so on
(i draw tail of vector at FROM end and head of vector at TO end, but that choice is made by your textbook author)
then recall from grade school geometry that two sides and an angle is all you need to define a triangle.
Now - voltage from any two phases to neutral and the 120 degree angle between them completely defines that triangle and all six voltages.
Cool, huh ?
Who said three phase is hard you just got to be meticulous.
..... anyhow....
On primary side neutral is grounded
so all you need is two phases and neutral (which is ground on distribution side)) to establish the voltage triangle.
.....
That's why there's only two high voltage wires
and ground
and a wye.
It's Electric Company;s choice. They save a transformer and some insulators and only have to maintain two HV connections..

You really should go through that drawing exercise for your edification,
(EDIT we actually call the lines "Phasors" but you treat them just like vectors)​

nextMaybe the above is not illustration of my 2 transformers..

That illustration would work
But I cannot see your transformers.
You need to spend the time to follow out all your wires , carefully sketching and double checking them.
Then you'll know if they ran that neutral all the way inside (in which case you would have 240/120 available)
and whether they earthed it.
Hopefully it's earthed somewhere because this

looks like neutral is bonded to the metal box
and if it's not earthed it could become elevated by a ground someplace on a phase..

​

.. do you know where to find illustration of wiring of my two transformers?
No, sorry.
And what does P in the right wire mean?
I don't have any clue,
but that's the leg that'd read 208 to neutral. In the US we call that one the "Wild Leg" . Is there a synonym for "wild" that starts with "P" ?

Thanks a lot!

 

[jim hardy]

Try a search on "Pole Pig Transformer" for a lot of images of them. The Wikipedia entry isn't bad.

 

[kiki_danc]

I can't see all the wires between the two transformers' low sides
It does appear there's a wire on centertap of the last one you posted.
but i don't see it earthed(grounded)
View attachment 231926​

What is that isolated piece of metal above below the middle wire.. I went to look at the transformer again. The wire at middle is connected to the neutral of my service panel and it is also connected to the rod stuck at concrete beside the pole. Is this enough to ground it.. or does grounding means the isolated piece of metal has to be connected to ground as well?

In the image below. It's bottom shot. The neutral tap at middle terminal is connected to the wire between poles.. isn't it the ground or is the ground the isolated piece of metal in the pic above?

I just want to make sure the utility company follow local codes.. because if they themselves don't follow and we don't know.. we can't do anything.

 

[jim hardy]

What is that isolated piece of metal above below the middle wire..

This ?

That's a connection point to :"bond" (connect) the low side centertap to the transformer's metal tank,
The practice in US is to ground every system at its source, and that transformer winding is the source for your building.
So placing a strap from centertap to that metal 'boss' connects it to the tank and the tank is grounded as in this photo from post # 195.

I went to look at the transformer again. The wire at middle is connected to the neutral of my service panel

Good! Now that's established as fact by direct observation.

and it is also connected to the rod stuck at concrete beside the pole. Is this enough to ground it.

Well at least it's grounded...

or does grounding means the isolated piece of metal has to be connected to ground as well?

I don't think it's isolated, it's welded to the tank and the tank is grounded.
So the question becomes "do your local authorities accept your connection down by the pole as "grounded at the source" ?
So far as i know here in US we interpret "at the source" to mean right at the transformer terminal. That;s why the provision for it there.
Your county might prefer separate grounds for primary and secondary - i don't know. That's a question for your electrical inspector and city engineer .

Here's a tutorial on grounding that you'll find informative...
https://pdfs.semanticscholar.org/presentation/eb8b/c74dcc7a017c81e98defeebcc5f68fdb0024.pdf

In the image below. It's bottom shot. The neutral tap at middle terminal is connected to the wire between poles.. isn't it the ground or is the ground the isolated piece of metal in the pic above?

This ?

That looks to me like the Neutral. Did they connect it to a wire or rod buried in the Earth ? You mentioned a rod near the pole...

Next time you see an electric company truck working, stop and talk with the crew. Ask them about grounding , how do they connect Neutral to earth.. They'll probably be happy to share their knowledge.

 

[kiki_danc]

This ?

View attachment 231951
That's a connection point to :"bond" (connect) the low side centertap to the transformer's metal tank,
The practice in US is to ground every system at its source, and that transformer winding is the source for your building.
So placing a strap from centertap to that metal 'boss' connects it to the tank and the tank is grounded as in this photo from post # 195. View attachment 231950
Good! Now that's established as fact by direct observation.Well at least it's grounded...I don't think it's isolated, it's welded to the tank and the tank is grounded.
So the question becomes "do your local authorities accept your connection down by the pole as "grounded at the source" ?
So far as i know here in US we interpret "at the source" to mean right at the transformer terminal. That;s why the provision for it there.
Your county might prefer separate grounds for primary and secondary - i don't know. That's a question for your electrical inspector and city engineer .

Here's a tutorial on grounding that you'll find informative...
https://pdfs.semanticscholar.org/presentation/eb8b/c74dcc7a017c81e98defeebcc5f68fdb0024.pdf
This ?

View attachment 231953

That looks to me like the Neutral. Did they connect it to a wire or rod buried in the Earth ? You mentioned a rod near the pole...

Next time you see an electric company truck working, stop and talk with the crew. Ask them about grounding , how do they connect Neutral to earth.. They'll probably be happy to share their knowledge.

Yes the centertap is connected to the rod at ground, they didn't use the small metal at the tank.. maybe because it's redundant since another terminal in the tank is connected to ground.. so it's as good as ground.. so for all intent and purposes, it's "grounded at the source" because a few meters of wires may not affect the impedance or whatever much. Hence connection down by the pole is as good as "grounded at the source".

And yes I will surely ask the electric company how they do all the neutral grounding. I think the problem are really the contractors. They are saving wires for the ground.

For example. In my home. I noticed my service entrance has the uninsulated neutral wire too, however after the meters, the old building contractors didn't put any lines .

Notice the lower wires getting inside the 6 apartments, there is no more ground from the neutral wires. Our city hall never check for ground, it is not a requirement that is why we have millions of homes without ground wires. Fortunately there is at the service entrance wire (in blue below):

I've talked to some local electrical engineers. They totally have no experience in grounding. My question is, if I'd let them tap the neutral at service entrance (with permission from the utility company) and put grounding wires to inside my house about 50 meters away (164 feet away) from the main panel breaker above and the total single phase amperage is 120 ampere.. what is the rule for the size of the grounding wire? Do you have reference for grounding wires sizes? Local electrical engineers are not sure because they rarely deal with ground. One commented to use the full live load wire size.. but then the grounding is only to trip the breaker for short instance or pulse.. so what is the minimum size for this? Of course I'll still discuss this with the engineers but just want some ideas as they don't know. Many thanks.

 

[kiki_danc]

Yes the centertap is connected to the rod at ground, they didn't use the small metal at the tank.. maybe because it's redundant since another terminal in the tank is connected to ground.. so it's as good as ground.. so for all intent and purposes, it's "grounded at the source" because a few meters of wires may not affect the impedance or whatever much. Hence connection down by the pole is as good as "grounded at the source".

And yes I will surely ask the electric company how they do all the neutral grounding. I think the problem are really the contractors. They are saving wires for the ground.

For example. In my home. I noticed my service entrance has the uninsulated neutral wire too, however after the meters, the old building contractors didn't put any lines .

View attachment 231959

Notice the lower wires getting inside the 6 apartments, there is no more ground from the neutral wires. Our city hall never check for ground, it is not a requirement that is why we have millions of homes without ground wires. Fortunately there is at the service entrance wire (in blue below):

View attachment 231960

I've talked to some local electrical engineers. They totally have no experience in grounding. My question is, if I'd let them tap the neutral at service entrance (with permission from the utility company) and put grounding wires to inside my house about 50 meters away (164 feet away) from the main panel breaker above and the total single phase amperage is 120 ampere.. what is the rule for the size of the grounding wire? Do you have reference for grounding wires sizes? Local electrical engineers are not sure because they rarely deal with ground. One commented to use the full live load wire size.. but then the grounding is only to trip the breaker for short instance or pulse.. so what is the minimum size for this? Of course I'll still discuss this with the engineers but just want some ideas as they don't know. Many thanks.

The following is my home items.. such as pure metal rice cookers and microwave oven ungrounded (because of lack of ground wires from service panel as the above pictures and details show)

However if I'll connect ground wires to them.. there is now directly conduction path to the high voltage transformers winding.. what if the transformers burn or suffer insulation problem then you have high current going direct to your rice cookers or microwave! Won't be this scarier? Or lightning getting into the neutral wires from the pole right to the rice cookers and microwave! there is no "ground" breakers.. so how do you isolate from those high current lines or fault? Are there folks here who avoid grounding for exactly these reasons?

 

[jim hardy]

what is the rule for the size of the grounding wire? Do you have reference for grounding wires sizes?

our electrical code gives guidance
try a search on "size of grounding conductor"

https://www.industry.usa.siemens.co...ducts/Documents/Grounding_Conductors_0507.PDF

Note that's the protective grounding conductor not the neutral

you ought to spend a few hours studying that section of your code.

 

[jim hardy]

It is the job of the grounding at the pole and service entrance to prevent that.

However lightning can do exactly what you describe. Happened to me once.
It's good practice to stay away from metal appliances when there's lightning in the neighborhood.

You will find these threads helpful.
https://www.physicsforums.com/threads/help-needed-with-static-electricity.529065/
https://www.physicsforums.com/threads/not-fully-understanding-grounds.622107/#post-4007190

and

https://www.physicsforums.com/threads/grounding-in-usa-residential-homes-with-240-120-panel.678977/
See post #10.

 

[kiki_danc]

It is the job of the grounding at the pole and service entrance to prevent that.

However lightning can do exactly what you describe. Happened to me once.
It's good practice to stay away from metal appliances when there's lightning in the neighborhood.

You will find this thread helpful.
https://www.physicsforums.com/threads/not-fully-understanding-grounds.622107/#post-4007190
See post #10.

Ok. I guess putting surge protectors between neutral and ground can minimize the shock(?) maybe that's why there is N-G (Neutral-Ground) protection mode besides L-N, L-G, N-G? Is this the purpose of the N-G mode? When you use the say Siemens 140,000A surge protector and a lightning with energy of 6000V, 130,000A hit the lines.. then the Siemens will absorb them leaving only the VPR of 600 volts?
Tom wrote earlier that
"Consider a nearby lightning strike that puts 6000V on the power line to ground. Much equipment is rated perhaps 600V or so from line to chassis, the the chassis is now at 6000V, and so is everything in it and connected to it. Is there anything near enough to the equipment that a 6000V spark can jump to? For instance the insulation in a transformer would likely break down if anything on its secondary is grounded or near a ground or a large conducting surface. If the transformer is mounted in an electrical box, the box would likely be grounded and the an arc would jump to the transformer core, to the box, to ground. If a person happens to be in contact with the equipment, he/she is now at 6000V; is the floor wet, person touching another piece of equipment at the same time?"

Anyway. I got so much information now that the most logical thing left is to start grounding all metal enclosure and know what surge protectors to use. I guess this is it. Thanks to all who supplied much useful and helpful information!

 

[jim hardy]

If a person happens to be in contact with the equipment, he/she is now at 6000V; is the floor wet, person touching another piece of equipment at the same time?"

Read in one of those links i posted my anecdote about holding a metal cased electric drill when lightning struck my power pole .
I learned most of what i understand about grounding in that visceral half second . I knew the instant it hit exactly what had happened.

So you use multiple protections wherever they're appropriate
grounding to limit voltage between people and earth
and double insulate to prevent current flow through people.In your above scenario ,
if lightning elevated local Earth to 6000 volts so the floor is also at 6000 volts then there's no potential difference to drive current through the person. That's why metal buildings are grounded .

You now have understanding of the principles of grounding
it will take you months to work out in your mind "what if" thought experiments that resolve apparent logical conflicts.
Kirchoff's laws of voltage and current are the thought tools.

have fun ,
and share your knowledge&experience with others as it grows..

 

[berkeman]

Thread is closed for a bit...

 

[Mark44]

The OP's question has been abundantly answered, so I'm closing this thread.