Understanding Surge Protector Specs for the Computer Age

[kiki_danc]

That came across as somewhat confusing! You won't get any significant current flow below the MCOV, if I recall correctly, they start to turn on at the clamping voltage (MCOV = Maximum Continuous Operating Voltage). And yes, either overvoltage or overcurrent will lead to failure.Here is the search I used: https://www.google.com/search?&q=surge+protector++vpr++330Never tried them, never heard of them before. Only found them with the above search.

Cheers,
Tom

p.s. Here is a link you may find interesting. https://www.nemasurge.org/faqs/

If you will notice.. most 120v SPD type 3 has VPR of 600 volts average. 330V VPR is so rare. If 600V VPR can still damage equipments.. why would people still buy surge protectors?

Reflecting on it. Maybe even VPR of 600v is safe for 120v equipments because the surge only last 8/20 microsecond? Maybe this is not enough to heat the electronic elements.. it's not like voltage regulator where 600v is continuous. So I guess 6000v surge may damage electronics but not 600v surge?

Also we mostly hear about VPR... how come we never hear about let-thru current. For example if a UL 1449 3rd edition 6000v, 3000A 8/20 microsecond surge hit the MOV. Besides the VPR of say 600 volts.. what is the CPR (Current Protection Rating if there is such a phrase) rating or value. Does the 3000A become like 400A only or is it completely gone after it passed the MOV element.. zero residual current? For electronic circuits.. what can damage it more.. voltage surge or current surge? And what electronic components are directly damaged by any surge? the transistors, the ICs? How is it damaged? If current is what damaged it.. then VPR of 600v and CPR (Current Protection Rating) of zero may no longer damage any electronics.. What do you think?

 

[kiki_danc]

Tom. For complete information of my power system. I found out my transformers power configuration is a 3 phase HIGH LEG delta (High leg open delta?) with one of the 3 phases to neutral measuring 208 volts instead of 120 volts... (this open delta composed of 2 transformers connected to only 2 primary source as detailed earlier).

I learned this after I let my electrician measured each of the phase to neutral voltage in my main panel yesterday:

See the right most breakers.
X1 to neutral is measured as approx. 210 volts (or 208 Volts).
X2 to neutral is measured as 120 volts.
X3 to neutral is measured as 120 volts.

But between X1-X2, X1-X3, X2-X3.. they are all 240 volts.

Now my admin breaker (in middle) is connected to the X1 and X2 producing split phase and hence the same as your US split phase 120/240Volts (my power system in my building is indeed more complicated than your US single phase home supply)

My question is, the X1, X2, X3 configuration in the transformers are permanent right? Or would there be unexpected rotations making X2 to neutral 208 volts instead of X1 to neutral. This is important because if the SPD supplier puts150Vac between my X2 to neutral and suddenly it becomes the hot 208V from transfomers, then the MOV thermal fuse would initiate thermal breakaway (or destroying the SPD in the process).

If there is no rotations. Our discussions were still valid even though X1 to neutral is 210 volts because it's high leg delta?

This thread is important to me because all my local SPD suppliers are selling me 3 phase SPD worth $2000. They don't know individual SPD can be connected line to line. So they just offered me either line to neutral or the very expensive 3 phase (which I don't need because no equipment of the building is actually 3 phase. the designer just make 3 phase power in the electrical plans because he is expecting 3 phase aircon (which we don't use). Therefore I appreciate so much all our discussions as my Siemens 140kA is on the way and it is 8 times less expensive and compatible with the X2 and X3 seen as single phase split phase 120/240V.

After all this. Maybe I should get a licensed in electrical engineering and deal with SPDs business locally as they are selling very expensive here and not many know how to connect it right.. lol...

 

[Tom.G]

As long as the "A" and "C" connections are on the transformer winding that has "X0" there will not be a problem with a phase sequence change.
Any change to cause different voltages on the wires would have to be physical, secondary side, wire changes to the transformers on the power pole.

I am curious though, if I recall correctly one of your earlier posts said their was 3 wires coming from the power pole to the service entrance. Which is OK. The question is: In the photo of the breakers, where do those 4 wires go that are on the Neutral? Equivalently, how is the Neutral derived locally since it is not brought in from the power pole

Cheers,
Tom?

 

[kiki_danc]

View attachment 231886

As long as the "A" and "C" connections are on the transformer winding that has "X0" there will not be a problem with a phase sequence change.
Any change to cause different voltages on the wires would have to be physical, secondary side, wire changes to the transformers on the power pole.

I am curious though, if I recall correctly one of your earlier posts said their was 3 wires coming from the power pole to the service entrance. Which is OK. The question is: In the photo of the breakers, where do those 4 wires go that are on the Neutral? Equivalently, how is the Neutral derived locally since it is not brought in from the power pole

Cheers,
Tom?

The 4 wires in the neutral bar connects to all the neutral in the building as well as the centertap of the 3 phase transfomers (Yes I individually traced where the 4 wires lead... they led to all the neutral subbar in the subpanels and outside to the service entrance 4 wire entrance). I paid the utility company $4000 for the 2 transformers that is why they tap their centertap to my panels. But for my own home.. no wire from centertap.. btw.. this office building is owned by many co-owners. I'm just one of them and in charge of administration.

 

[kiki_danc]

If you will notice.. most 120v SPD type 3 has VPR of 600 volts average. 330V VPR is so rare. If 600V VPR can still damage equipments.. why would people still buy surge protectors?

Reflecting on it. Maybe even VPR of 600v is safe for 120v equipments because the surge only last 8/20 microsecond? Maybe this is not enough to heat the electronic elements.. it's not like voltage regulator where 600v is continuous. So I guess 6000v surge may damage electronics but not 600v surge?

Also we mostly hear about VPR... how come we never hear about let-thru current. For example if a UL 1449 3rd edition 6000v, 3000A 8/20 microsecond surge hit the MOV. Besides the VPR of say 600 volts.. what is the CPR (Current Protection Rating if there is such a phrase) rating or value. Does the 3000A become like 400A only or is it completely gone after it passed the MOV element.. zero residual current? For electronic circuits.. what can damage it more.. voltage surge or current surge? And what electronic components are directly damaged by any surge? the transistors, the ICs? How is it damaged? If current is what damaged it.. then VPR of 600v and CPR (Current Protection Rating) of zero may no longer damage any electronics.. What do you think?

Anyway I read here about the 330V thing and they are also promoting series filters that don't use MOVs... I wonder if these are gimmicks...

https://www.labmanager.com/laboratory-technology/2014/05/surge-suppression#.W7rOQPZuKh1

"Your computer and laboratory test equipment have semiconductor components such as diodes and transistors that are rated for various voltage/current combinations, but most need to operate below 330 volts. Above 330 volts, pinholes and melt spots occur within the component, which over time leads to failure. This process is analogous to an erosion process that is caused by a small but potent force over time. Again, because a surge is both a rise in voltage and a rise in current, it is important to protect your equipment from both the sudden change in voltage (dV/dt) and current (di/dt)."
<snip>
"
Simplified schematic of a series mode filter. There are no sacrificial components, so the filter does not wear down with use, and it repeatedly eliminates surges.Series mode filter technology (real-time suppression)
Another approach is to first consider what a surge really is—a high-frequency noise comprising a rise in voltage and a rise in current that occurs over a period of time. Surges are an unwanted component of the electricity you do want to reach your equipment. Instead of diverting the surge energy, let us consider a method that filters the unwanted surge.

Filtering the surge requires a device that is placed in series with the electric power. Because the filter has to be good enough to limit the voltage rise as well as the inrush of current, there have to be several stages of filtration. The first stage is an inductor coil. A properly designed inductor can choke the higher-frequency noise (i.e., the surge), letting the lower-frequency AC power wave pass through. The second stage is a series of components (mostly capacitors) to keep the voltage to a desired level. By combining these two stages, one could effectively stop the voltage rise and the inrush of current. The surge energy ends up being converted to useful energy and some negligible heat.

Learning from our MOV discussion, we ask about the MCOV and VPR for series mode filters. Do they have the same issues? The answer is no! The VPR for a series mode filter is tested to the lowest 330-volt rating but also has a high MCOV at 175 volts. A series mode filter does not have a joule rating because it does not have a sacrificial component as an MOV does. In fact, a properly designed series mode filter can withstand 1,000 of the worst-case surges (6,000 volts / 3,000 amps) applied in 30-second pulses."

These are supporting a product owned by zero surge company.. here's another message and I wonder if the information is factual.. it said:

Why Whole Building Surge Protectors Don't Work

"Lower VPR Needed
The lower VPR product turns on first, limiting the surge to 400 volts, well below the 700 volt panel protector clamping rating — making the higher VPR "whole building" main panel and branch circuit protectors useless, and the point-of-use protector the actual "first line of defense".

"Whole building" and panel protectors with VPRs of 700 volts or more, are ineffective when the required lower clamping level plug-in protectors are on the same circuit, because the lower clamping level product will clamp first and do all the work! The claim that the "whole building" protector is the first line of defense is incorrect."

Is it correct information? He is supporter of the Zero Surge product... isn't it if two products have VPR of 400v and 700v and have same MCOV of say 150V. They will clamp at same time if voltage goes above 150V? Or is he correct the product with VPR of 400v will clamp first? Clamping is supposed to be when the MOV starts to short.. and isn't it this occurs above the MCOV and not the VPR. Just verifying to be sure we are not being fooled by manufacturers.. One can directly order these series filters from their website and so attractive to us overseas people:

https://zerosurge.com/plug-in-products-solutions/

 

[kiki_danc]

The 4 wires in the neutral bar connects to all the neutral in the building as well as the centertap of the 3 phase transfomers (Yes I individually traced where the 4 wires lead... they led to all the neutral subbar in the subpanels and outside to the service entrance 4 wire entrance). I paid the utility company $4000 for the 2 transformers that is why they tap their centertap to my panels. But for my own home.. no wire from centertap.. btw.. this office building is owned by many co-owners. I'm just one of them and in charge of administration.

My service entrance is really 4 wire (not 3 as I mentioned earlier).. I counted them, the 4th small wire is the neural wire hopefully connected to the centertap of the transformers.. I said "hopefully" because it goes to the pole but electrical engineers in my country talked about "floating ground".. that it's not connected to the centertap but just to ground besides the pole. When I have time. I'll use my high resolution binocular to see if the wire is connected to the centertap (after trying to learn where exactly is the centertap located in the transformers).

 

[kiki_danc]

View attachment 231888

My service entrance is really 4 wire (not 3 as I mentioned earlier).. I counted them, the 4th small wire is the neural wire hopefully connected to the centertap of the transformers.. I said "hopefully" because it goes to the pole but electrical engineers in my country talked about "floating ground".. that it's not connected to the centertap but just to ground besides the pole. When I have time. I'll use my high resolution binocular to see if the wire is connected to the centertap (after trying to learn where exactly is the centertap located in the transformers).

Could one argue that since X1 to neutral is measured as 208volts then the centertap was used. or can you also measure 208volts even when it's a floating ground (not actually connected to the transformers centertap)?

Also where is the location of the centertap of transformers?

Should it be at the center (of 3 terminals) in the right or can it be any terminal or leads in the left picture (above the red question mark?) This is just theoretical and to know if the centertap is indeed tapped. As I explained in another thread. Our utility company is saving wires that's why most homes don't have the centertap connected with wires to the service entrance panel.

 

[Tom.G]

That labmanager article you referenced has a few statements that do not reflect how the Universe operates (aka reality), which make me skeptical. However the basic premise is valid, that there are more approaches than using MOVs.

The ZeroSurge device may be appropriate for type 3 SPD usage when used with a transformer at the point-of-use whose primary is protected with a type 2 or type 3 SPD, and when one secondary terminal is Grounded.

There is not enough information available on the ZeroSurge website or on their data sheet for an in depth engineering evaluation.

I did a quick approximation of the minimum requirements for a Series Mode filter without an on-site transformer and came up with a requirement for 3 capacitors of 350μF at 400V, rated for pulse operation, and some inductors (coils). I found one capacitor that meets some, but not all, of the requirements. It is 3 inches in diameter, 9.5 inches long, and costs $85 USD. The rating it fails is the pulse voltage, and does so badly; maximum 12.5V/μS; the UL standard waveform is 750V/μS (6000V/8μs)

For the power pole transformers, I will defer to @jim hardy as he is the resident power plant guy. Jim, note that the pots have only one HV insulator each.

Cheers,
Tom

 

[kiki_danc]

That labmanager article you referenced has a few statements that do not reflect how the Universe operates (aka reality), which make me skeptical. However the basic premise is valid, that there are more approaches than using MOVs.

The ZeroSurge device may be appropriate for type 3 SPD usage when used with a transformer at the point-of-use whose primary is protected with a type 2 or type 3 SPD, and when one secondary terminal is Grounded.

There is not enough information available on the ZeroSurge website or on their data sheet for an in depth engineering evaluation.

I did a quick approximation of the minimum requirements for a Series Mode filter without an on-site transformer and came up with a requirement for 3 capacitors of 350μF at 400V, rated for pulse operation, and some inductors (coils). I found one capacitor that meets some, but not all, of the requirements. It is 3 inches in diameter, 9.5 inches long, and costs $85 USD. The rating it fails is the pulse voltage, and does so badly; maximum 12.5V/μS; the UL standard waveform is 750V/μS (6000V/8μs)

For the power pole transformers, I will defer to @jim hardy as he is the resident power plant guy. Jim, note that the pots have only one HV insulator each.

Cheers,
Tom

I came across the Zero Surge after googling about "VPR 330v" searching for another product like the Erico TSF6A120V. But I can't seem to find much. In fact, although 330v VPR were mentioned a lot.. none of the strip surge protectors at Amazon is proven to be 330v VPR. Most of them are not even UL listed.. and it is possible Erico 330v value is just the 2nd edition SVR which uses 500A instead of the 3rd edition 3000A test surge.. I wonder if UL indeeds test each Erico product. It's odd it's the only one in the planet that can really do it... unless something is not right.. So without real tests of 330v coming from 6000V, 3000A surge signal.. I think this whole 330v VPR thing may even be a myth with most really only lowest actual VPR of 500v. I'm still researching on this.

 

[Tom.G]

I think this whole 330v VPR thing may even be a myth

Well, if you don't believe Erico datasheet, why believe anybody elses?

 

[kiki_danc]

Well, if you don't believe Erico datasheet, why believe anybody elses?

according to the site: https://www.labmanager.com/laboratory-technology/2014/05/surge-suppression#.W7ryhPZuIUC

"Plug in type suppressors will typically have a VPR of 330 volt (ideal) but will have a 127 volt MCOV (not ideal—too close to line voltage). Suppressors installed at the service panel will generally have a safer MCOV (175 volts) but a much higher VPR of 600 to 1,000 volts (also not ideal—damaging to sensitive electronics)."

Now here is Erico TSF6A120V spec sheet:

You see.. the Erico MCOV is 170V. earlier website said 330v belong to MCOV of 125V. So it's odd when other manufacturers can't do a 330v with MCOV of 150Vac.

Also I think it's possible many are confusing SVR and VPR value. The 330V seems to belong to SVR. With the 3000A (versus 500A test surge) of VPR, I wonder if it can really come up with 330V VPR similar to SVR. I'm still googling other genuine products with 330Vac VPR at MCOV of 150Vac.. even Leviton, Siemens, and Eaton can't do it.. so I wonder if the others can that these giants can't...

 

[kiki_danc]

according to the site: https://www.labmanager.com/laboratory-technology/2014/05/surge-suppression#.W7ryhPZuIUC

"Plug in type suppressors will typically have a VPR of 330 volt (ideal) but will have a 127 volt MCOV (not ideal—too close to line voltage). Suppressors installed at the service panel will generally have a safer MCOV (175 volts) but a much higher VPR of 600 to 1,000 volts (also not ideal—damaging to sensitive electronics)."

Now here is Erico TSF6A120V spec sheet:

View attachment 231893

You see.. the Erico MCOV is 170V. earlier website said 330v belong to MCOV of 125V. So it's odd when other manufacturers can't do a 330v with MCOV of 150Vac.

Also I think it's possible many are confusing SVR and VPR value. The 330V seems to belong to SVR. With the 3000A (versus 500A test surge) of VPR, I wonder if it can really come up with 330V VPR similar to SVR. I'm still googling other genuine products with 330Vac VPR at MCOV of 150Vac.. even Leviton, Siemens, and Eaton can't do it.. so I wonder if the others can that these giants can't...

And here's a case in point regarding one of amazon best selling surge protector products: https://www.amazon.com/dp/B000J2EN4S/?tag=pfamazon01-20

And the FAQ says: (official belkins website spec link of it is https://www.belkin.com/us/p/P-BE112234-10/ (click specifications))

"What is the clamping voltage of BE112234-08? Official Belkins website says 330V but amazon's description says 500V
Answer:
UL Clamping Voltage (3-Line): UL 1449 500V Copied right from the box .
By Timothy D. Haupt on May 20, 2014
Reading off of the item in my hand its Stamped "Voltage Protection rating L-N 400V, L-G 500V, N-G 500V Type 3 SPD
My model number on mine says BE11230-08 so there may have been a change.
By Buddy on May 20, 2014 "

Note the term "clamping voltage" is ambiguous because it can refer to UL 1449 2nd edition or 3rd Edition. So Belden website could be sharing 2nd edition data of 330V (that uses 500A surge test signal). While in amazon and reality.. it's 500V per 3rd edition test surge of 3000A. Therefore it seems all type 3 SPD no matter how small average about 500Vac VPR.. and if electronic components can fail above 330V.. then perhaps we can say all SPDs in the planet doesn't really protect electronic that is sensitive down to 330v??

 

[kiki_danc]

And here's a case in point regarding one of amazon best selling surge protector products: https://www.amazon.com/dp/B000J2EN4S/?tag=pfamazon01-20

And the FAQ says: (official belkins website spec link of it is https://www.belkin.com/us/p/P-BE112234-10/ (click specifications))

"What is the clamping voltage of BE112234-08? Official Belkins website says 330V but amazon's description says 500V
Answer:
UL Clamping Voltage (3-Line): UL 1449 500V Copied right from the box .
By Timothy D. Haupt on May 20, 2014
Reading off of the item in my hand its Stamped "Voltage Protection rating L-N 400V, L-G 500V, N-G 500V Type 3 SPD
My model number on mine says BE11230-08 so there may have been a change.
By Buddy on May 20, 2014 "

Note the term "clamping voltage" is ambiguous because it can refer to UL 1449 2nd edition or 3rd Edition. So Belden website could be sharing 2nd edition data of 330V (that uses 500A surge test signal). While in amazon and reality.. it's 500V per 3rd edition test surge of 3000A. Therefore it seems all type 3 SPD no matter how small average about 500Vac VPR.. and if electronic components can fail above 330V.. then perhaps we can say all SPDs in the planet doesn't really protect electronic that is sensitive down to 330v??

Anyway. I think the best thing to do is to write Underwriters Laboratory (UL) and request list of products that has 330V results under UL 1449 third/4th edition. I wonder if they would honor such request? Anyone has tried dealing with UL? I saw the following specs:

http://www.eaton.com/ecm/groups/public/@pub/@electrical/documents/content/td158002en.pdf

330V is a 2nd edition thing.. but if a product under 3rd edition is 360V.. it is better than nothing.

This is time consuming to search for specs. If UL won't give me list. Perhaps I could just get the very expensive $380 Erico.. but it hurts the pocket. I could have better spent it elsewhere.. or maybe will settle for the Leviton 5100-PS which has 600v VPR. It goes back to this important question. What part of electronic circuits really get damaged by quick 600v surge? If none and it won't heat up.. then I guess we all can settle for 600v VPR at fraction of cost of 330v VPR SPD type 3 that we are not even sure is such (for example the 175Vac MCOV Erico). Say aren't others interested in surge protectors? We all can benefit from this so please ask your nearest UL representative to get the listing.

 

[kiki_danc]

Anyway. I think the best thing to do is to write Underwriters Laboratory (UL) and request list of products that has 330V results under UL 1449 third/4th edition. I wonder if they would honor such request? Anyone has tried dealing with UL? I saw the following specs:

http://www.eaton.com/ecm/groups/public/@pub/@electrical/documents/content/td158002en.pdf

View attachment 231897

330V is a 2nd edition thing.. but if a product under 3rd edition is 360V.. it is better than nothing.

This is time consuming to search for specs. If UL won't give me list. Perhaps I could just get the very expensive $380 Erico.. but it hurts the pocket. I could have better spent it elsewhere.. or maybe will settle for the Leviton 5100-PS which has 600v VPR. It goes back to this important question. What part of electronic circuits really get damaged by quick 600v surge? If none and it won't heat up.. then I guess we all can settle for 600v VPR at fraction of cost of 330v VPR SPD type 3 that we are not even sure is such (for example the 175Vac MCOV Erico). Say aren't others interested in surge protectors? We all can benefit from this so please ask your nearest UL representative to get the listing.

I find something very useful. One can see all UL listed products here:

http://productspec.ul.com/document.php?id=VZCA.E109835

The above is example of all Eaton listed UL products.. you can see only their MCOV of 127Vac can make it to 330V VPR.. while for 150Vac MCOV.. the VPR average is 600 volts.

Now the following is for Erico:

http://productspec.ul.com/document.php?id=VZCA.E325047

Their average VPR for 150Vac MCOV is 800Vac! The TSF5A120V is not listed. Therefore the 330V rating for this may be from older SVR.

Now for Belkin product: http://productspec.ul.com/document.php?id=VZCA.E152555

Their power strips being sold at amazon all have MCOV of only 127Vac.. (too close to 120Vac!)…

Therefore conclusion. There is no product that is actually tested for MCOV of 150Vac and VPR of 330V. All VPR of 330V either are below 150Vac or the older SVR 2nd edition. Can anyone contest my statement?

If I'm right. Then a 150Vac MCOV and VPR of 500 to 600v is the optimum spec for SPD type 3 and there is no VPR of 330V for 150Vac or higher MCOV. All else is fake news.. (Hence Erico spec for the TSF5A120V was from 2nd edition data using much weaker surge current).

 

[jim hardy]

Also where is the location of the centertap of transformers?

Look here

 

[jim hardy]

Could one argue that since X1 to neutral is measured as 208volts then the centertap was used. or can you also measure 208volts even when it's a floating ground (not actually connected to the transformers centertap)?

208 suggests that they used the centertap
but in absence of neutral current , voltage drop along Earth won't be much so you could well read 208 volts.

So you'd have to verify the presence of a neutral wire by either
1. verifying that you still get 208 volts when a few tens of amps flow into neutral
or
2. seeing the wire with your own eyes.

 

[kiki_danc]

I find something very useful. One can see all UL listed products here:

http://productspec.ul.com/document.php?id=VZCA.E109835

The above is example of all Eaton listed UL products.. you can see only their MCOV of 127Vac can make it to 330V VPR.. while for 150Vac MCOV.. the VPR average is 600 volts.

Now the following is for Erico:

http://productspec.ul.com/document.php?id=VZCA.E325047

Their average VPR for 150Vac MCOV is 800Vac! The TSF5A120V is not listed. Therefore the 330V rating for this may be from older SVR.

Now for Belkin product: http://productspec.ul.com/document.php?id=VZCA.E152555

Their power strips being sold at amazon all have MCOV of only 127Vac.. (too close to 120Vac!)…

Therefore conclusion. There is no product that is actually tested for MCOV of 150Vac and VPR of 330V. All VPR of 330V either are below 150Vac or the older SVR 2nd edition. Can anyone contest my statement?

If I'm right. Then a 150Vac MCOV and VPR of 500 to 600v is the optimum spec for SPD type 3 and there is no VPR of 330V for 150Vac or higher MCOV. All else is fake news.. (Hence Erico spec for the TSF5A120V was from 2nd edition data using much weaker surge current).

I checked many products in the Surge Protection Section at the UL sites above. There is none literally of 330vac VPR under 150Vac MCOV. Only for 127Vac MCOV. And 127Vac is too close to 120V and fire hazard. So I finally ordered 3 pcs of the Leviton 5100-PS with listed VPR of 500Vac and 150Vac MCOV. NOw transformer is supposed to have impedance so I can remove my 5 meters of loop. But how exactly do you calculate for transformer impedance and equivalent wire length (10 AWG) so it equals 5 meters.. so I can start searching for 220v-110v step down transformers?

 

[jim hardy]

For the power pole transformers, I will defer to @jim hardy as he is the resident power plant guy. Jim, note that the pots have only one HV insulator each.

https://en.wikipedia.org/wiki/Distribution_transformer

Wye – On a wye distribution circuit, a 'wye' or 'phase to neutral' transformer is used. A single phase wye transformer usually has only one bushing on top, connected to one of the three primary phases. The other end of the primary winding is connected to the transformer's case, which is connected to the neutral wire of the wye system, and is also grounded. A wye distribution system is preferred because the transformers present unbalanced loads on the line that cause currents in the neutral wire and are then grounded.

Colloquially they're known as "Pole Pigs".

 

[kiki_danc]

208 suggests that they used the centertap
but in absence of neutral current , voltage drop along Earth won't be much so you could well read 208 volts.

So you'd have to verify the presence of a neutral wire by either
1. verifying that you still get 208 volts when a few tens of amps flow into neutral
or
2. seeing the wire with your own eyes.

No. I won't experiment by tapping the 208 volts because I don't want the electrician to accidentally make wrong connections and trip the breakers. I'll just try to see the wires from distance using my high resolution binocular. But here is the picture of the actual transformers.

The middle terminal at right transformer is not wired.. but the middle terminal of the left transformer is wired.. based on the image.. is the neutral tapped to centertap? What is that thing above the red arrow?

​

Do you have exact wiring illustration for 3 phase open high leg delta transformers that connect to only 2 out of 3 wires in the primary high tension (I heard they use the 3rd wiring using the ground) see: https://www.practicalmachinist.com/...nd-vfd/three-phase-only-two-wires-wtf-103191/

 

[jim hardy]

based on the image.. is the neutral tapped to centertap? What is that thing above the red arrow?

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%

 

[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.