Understanding Surge Protector Specs for the Computer Age

[kiki_danc]

Yes, the Red looks to be the long-lost third wire. And the diagram in post #85 is similar to what I suspected when you said only 2 wires, I just wasn't familiar with the Open Delta configuration. (I learned something new. GREAT!)

But I still don't comprehend why you won't supply 120V thru a transformer to the 24VDC supply. The 240V SPDs won't keep the spikes below the 300V input rating of the supply. That was a limitation you stated earlier in the thread. Can you explain?

Cheers,
Tom

I just talked to the power company electrical engineering team. They explained to me that it's government compliance.. back in the 1990s they received order from government never to use line to ground.. this is promote local manufacturers who produced 220 volts appliance.. because if we can use 120 volts.. we could order stuff from the US and our country would lose revenue..so they never allow any applications to be tapping from line to ground.. only line to line.. and if city hall inspect and saw our connection has line to ground.. we may be cited for violation. I guess this answered your question. But then you haven't answered.. if the US 120 volts line connect to ground.. and you touch the ground.. why don't you get electrocuted?

I also asked about the transformer. They confirmed it's Open Delta for 2 transformers of 75 Kva and below. When the usage increases above 150 Kva, then they change to 3 piece WYE transformers..

But if I'll have 220Vac SPD type 3 near equipment cascaded to the 220Vac SPD type 2 at breaker with 220 volts supply.. won't the voltage be below 300 volts? Well.. even if the residual VPR at type 2 is say 3000 volts.. won't it decrease down to 220 volts at the type 3 end?

 

[Tom.G]

That's an interesting explanation of 'No 120V'. It even sort of makes sense. What country are you in?

But then you haven't answered.. if the US 120 volts line connect to ground.. and you touch the ground.. why don't you get electrocuted?

Because the Neutral at the transformer is grounded, AND that Neutral is brought to the breaker box where it is also grounded, AND the Green Earth 'Ground' wire is also connect to Neutral at the breaker box. If the 120V shorts to Ground it is the same as shorting to Neutral, the short essentially short-circuits the transformer and the circuit breaker trips.

For supplying the 24VDC supply, if you use a transformer connected to 240V you are meeting the non-120V requirement and getting the opportunity of better protection for the 24VDC supply. If you have an electric doorbell, it likely runs on about 16VAC from a transformer, which makes it comply with the 240V requirement.

Cheers,
Tom

 

[Tom.G]

That's an interesting explanation of 'No 120V'. It even sort of makes sense. What country are you in?

But then you haven't answered.. if the US 120 volts line connect to ground.. and you touch the ground.. why don't you get electrocuted?

Because the Neutral at the transformer is grounded, AND that Neutral is brought to the breaker box where it is also grounded, AND the Green Earth 'Ground' wire is also connect to Neutral at the breaker box. If the 120V shorts to Ground it is the same as shorting to Neutral, the short essentially short-circuits the transformer and the circuit breaker trips.

For supplying the 24VDC supply, if you use a transformer connected to 240V you are meeting the non-120V requirement and getting the opportunity of better protection for the 24VDC supply. If you have an electric doorbell, it likely runs on about 16VAC from a transformer, which makes it comply with the 240V requirement.

Cheers,
Tom

 

[kiki_danc]

That's an interesting explanation of 'No 120V'. It even sort of makes sense. What country are you in?Because the Neutral at the transformer is grounded, AND that Neutral is brought to the breaker box where it is also grounded, AND the Green Earth 'Ground' wire is also connect to Neutral at the breaker box. If the 120V shorts to Ground it is the same as shorting to Neutral, the short essentially short-circuits the transformer and the circuit breaker trips.

For supplying the 24VDC supply, if you use a transformer connected to 240V you are meeting the non-120V requirement and getting the opportunity of better protection for the 24VDC supply. If you have an electric doorbell, it likely runs on about 16VAC from a transformer, which makes it comply with the 240V requirement.

Cheers,
Tom

You mean using the 150Vac SPD at the secondary end of a 220V primary & 120 volt secondary transformer? I haven't thought of that. But I guess the transformer may not fit inside the circuit panel. And you will have long lead wires enough to bring VPR up high back to 220 volt reference level. If you will put the transformer near the equipment.. you mean using 320 Vac SPD at breakers and 150 Vac SPD at equipment?

 

[Tom.G]

Yes, that's what I was trying to say in post #62 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-4#post-6064111).
320V SPD at transformer primary and 150V SPD at the equipment. Doesn't matter where the transformer is physically placed.

And you haven't answered... What country are you in?

 

[kiki_danc]

Yes, that's what I was trying to say in post #62 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-4#post-6064111).
320V SPD at transformer primary and 150V SPD at the equipment. Doesn't matter where the transformer is physically placed.

And you haven't answered... What country are you in?

By 320V Spd at transformer primary, you mean two 150Vac SPD in series (for phase a to ground and phase b to ground we discussed earlier) giving total of 300Vac.. or maybe you mean line to line 320V SPD. I'd prefer the latter because the former is artificial. In the US, you have hot wire to neutral so it's natural to put one SPD to ground. But for line to line... creating two SPDs in series with ground at middle is kinda artificial.. isn't it. So I need to buy a line to line SPD at breaker.

For the equipment. Since I'd cascade type 3 SPD to type 3 at breaker, voltage from type 3 would be further suppressed to 220 volts.. so why do I have to use transformers.. problem is.. if the transformer gets defective, the MOV element may end up in flame.. Also if you use transformers.. the 120 volts line to ground would become 60 volts.. and there is no 60 volts SPD.. if you use 150 volts SPD just one piece.. it won't work.. it must be two piece since you are protecting line to line... or the new illustration for the transformer secondary end...

I'd msg you in prv for the country for security reasons.

 

[kiki_danc]

By 320V Spd at transformer primary, you mean two 150Vac SPD in series (for phase a to ground and phase b to ground we discussed earlier) giving total of 300Vac.. or maybe you mean line to line 320V SPD. I'd prefer the latter because the former is artificial. In the US, you have hot wire to neutral so it's natural to put one SPD to ground. But for line to line... creating two SPDs in series with ground at middle is kinda artificial.. isn't it. So I need to buy a line to line SPD at breaker.

For the equipment. Since I'd cascade type 3 SPD to type 3 at breaker, voltage from type 3 would be further suppressed to 220 volts.. so why do I have to use transformers.. problem is.. if the transformer gets defective, the MOV element may end up in flame.. Also if you use transformers.. the 120 volts line to ground would become 60 volts.. and there is no 60 volts SPD.. if you use 150 volts SPD just one piece.. it won't work.. it must be two piece since you are protecting line to line... or the new illustration for the transformer secondary end...

View attachment 231462

I'd msg you in prv for the country for security reasons.

If I'm right above that there is no lower than 150 Vac MCOV SPD (the label at right must be 150 instead of 120) and it can't work. Then the only solution is to buy 2 Siemens 120/240V split phase type 1. However, I'd use it as type 2 and type 3. So I guess this will solve all.

Hope you can state now if you don't have adverse comment so I can proceed and finally leave this thread behind. I'm been occupied for this for a week and away from string theory and I feel guilty. Thanks so much Tom.

 

[Tom.G]

Since I'd put type 3, voltage from type 2 would be further suppressed to 220 volts

No it won't. It will be suppressed to between 420V and 1200V per the datasheet you supplied in post #52 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-3#post-6063218) or between 420V and 2000V per the datasheet you supplied in post #26 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-2#post-6060374)

Ideally, the most protection is to use 3 MOVs at the primary and 3 at the load. This will catch both common mode and line-to-line surges.

Then do the same at the primary using 240Vac MOVs. Of course you can use pre-built SPDs.

By the way, decide what you want to happen when an SPD fails shorted.

• Shut off power to the load when they fail, thereby protecting it from further surges.
• Disconnect the MOVs from the circuit while keeping power to the load, but they no longer protect the load.

When most SPDs fail they fail shorted, and will trip the circuit breaker feeding them to remove power.
The one you showed in post #52 is the second option, it keeps power to the load and blows an internal fuse to disconnect a shorted MOV.

You need a fuse or circuit breaker in the power feed to the SPD for the first option.
But don't try to add an external fuse to get the effect of the second option. The fuse sizing and design is a science in itself. Let the manufacturer do it.

Can we put this project to bed yet?

Cheers,
Tom

 

[kiki_danc]

No it won't. It will be suppressed to between 420V and 1200V per the datasheet you supplied in post #52 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-3#post-6063218) or between 420V and 2000V per the datasheet you supplied in post #26 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-2#post-6060374)

What? You mean even if the output of type 2 from breaker is 1200 volts VPR.. when this inputs into the type 3, it won't get lowered down? Remember the 1200 volts is the voltage output from type 2.. meaning it's the residual voltage instead of 6000 Volts... so when you have voltage that low already.. a type 3 can suppress it down to 220 volts.. Or to make an easier example.. supposed you stand alone type 2 has only surge of 1300 volts.. won't that stand alone spd suppress it down to 220 volts??

Ideally, the most protection is to use 3 MOVs at the primary and 3 at the load. This will catch both common mode and line-to-line surges.

View attachment 231464

Then do the same at the primary using 240Vac MOVs. Of course you can use pre-built SPDs.

By the way, decide what you want to happen when an SPD fails shorted.

• Shut off power to the load when they fail, thereby protecting it from further surges.
• Disconnect the MOVs from the circuit while keeping power to the load, but they no longer protect the load.

When most SPDs fail they fail shorted, and will trip the circuit breaker feeding them to remove power.
The one you showed in post #52 is the second option, it keeps power to the load and blows an internal fuse to disconnect a shorted MOV.

You need a fuse or circuit breaker in the power feed to the SPD for the first option.
But don't try to add an external fuse to get the effect of the second option. The fuse sizing and design is a science in itself. Let the manufacturer do it.

Can we put this project to bed yet?

Cheers,
Tom

 

[Tom.G]

won't that stand alone spd suppress it down to 220 volts??

What does the datasheet say about the type 3 you are proposing? I've lost track of all of the ones we've discussed.

 

[kiki_danc]

No it won't. It will be suppressed to between 420V and 1200V per the datasheet you supplied in post #52 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-3#post-6063218) or between 420V and 2000V per the datasheet you supplied in post #26 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-2#post-6060374)

Ideally, the most protection is to use 3 MOVs at the primary and 3 at the load. This will catch both common mode and line-to-line surges.

View attachment 231464

This is the part that I want to understand from the beginning. If your power supply is line to line and your equipment is line to line.. how can common mode occurs when your equipment is not grounded.. and even if there is surge at line to ground.. how can it damage the equipment?

Then do the same at the primary using 240Vac MOVs. Of course you can use pre-built SPDs.

So in the primary. I'd put 320 Vac MOV across the 220 volts line to line.. and 150 Vac MOV from line 1 to ground and line 2 to ground? meaning I'd be using 5 pieces of 150 Vac MOV and one 320 Vac MOV?

By the way, decide what you want to happen when an SPD fails shorted.

• Shut off power to the load when they fail, thereby protecting it from further surges.
• Disconnect the MOVs from the circuit while keeping power to the load, but they no longer protect the load.

When most SPDs fail they fail shorted, and will trip the circuit breaker feeding them to remove power.
The one you showed in post #52 is the second option, it keeps power to the load and blows an internal fuse to disconnect a shorted MOV.

You need a fuse or circuit breaker in the power feed to the SPD for the first option.
But don't try to add an external fuse to get the effect of the second option. The fuse sizing and design is a science in itself. Let the manufacturer do it.

Can we put this project to bed yet?

Cheers,
Tom

What does the datasheet say about the type 3 you are proposing? I've lost track of all of the ones we've discussed.

Let's take this 320Vac SPD...

If the surge is 6000 volts, 3000 ampere at 8/20 microsecond.. VPR is 1200 volts...
However if the surge is only say 1300 volts.. 500 ampere at 8/20 microsecond.. won't the VPR become say 100 volts only or so?

Edit: I mean won't the voltage becomes 100 volts only or so way below the VPR rating?

 

[kiki_danc]

This is the part that I want to understand from the beginning. If your power supply is line to line and your equipment is line to line.. how can common mode occurs when your equipment is not grounded.. and even if there is surge at line to ground.. how can it damage the equipment?So in the primary. I'd put 320 Vac MOV across the 220 volts line to line.. and 150 Vac MOV from line 1 to ground and line 2 to ground? meaning I'd be using 5 pieces of 150 Vac MOV and one 320 Vac MOV?

Let's take this 320Vac SPD...

View attachment 231466

If the surge is 6000 volts, 3000 ampere at 8/20 microsecond.. VPR is 1200 volts...
However if the surge is only say 1300 volts.. 500 ampere at 8/20 microsecond.. won't the VPR become say 100 volts only or so?

Edit: I mean won't the voltage becomes 100 volts only or so way below the VPR rating?

See this illustration for the above...

So type 3 would only have very low voltage way below the VPR.. why is this wrong?

(also note the 420 V you were mentioning were really DC in the specs)

 

[Tom.G]

This is the part that I want to understand from the beginning. If your power supply is line to line and your equipment is line to line.. how can common mode occurs when your equipment is not grounded.. and even if there is surge at line to ground.. how can it damage the equipment?

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?

So in the primary. I'd put 320 Vac MOV across the 220 volts line to line.. and 150 Vac Move from line 1 to ground and line 2 to ground? meaning I'd be using 5 pieces of 150 Vac MOV and one 320 Vac MOV?

This one I will back off from a bit, I tend to think how the wiring HERE is done. The SPDs you had installed in the breaker box were a very good start, leave them in. Now add a line-to-line SPD at the transformer primary.

Let's take this 320Vac SPD...

In line 4 of the table see "MCOV (VAC/VDC)" it says (320/420). That is saying you can put 420VDC on the input continuously and the device will ignore it, that it will not conduct.

Now go to line 7, "Voltage protection rating" "VPR" this shows "<1.2kV" meaning that the maximum clamping voltage is not greater than 1200V.

However if the surge is only say 1300 volts.. 500 ampere at 8/20 microsecond.. won't the VPR become say 100 volts only or so?

So type 3 would only have very low voltage way below the VPR.. why is this wrong?

That is an ASSUMPTION on your part. The manufacturer is only guaranteeing that the output is less than 1.2kV. How much equipment do you want to gamble that your assumption is more accurate than the manufacturers explicit statement?

Cheers,
Tom

 

[kiki_danc]

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?

Thanks for this info. In my country, most electrician never connect metallic chassic to ground. They just cut the ground wire.. and before this week I didn't know the purpose was to trip the breaker in case line touches metallic chassic and not electrocute the person (most electricians ignore this). From now on. I'll ensure all metallic chassic is grounded.. we never did it before. Even the refrigerator in my house and aircon are not grounded at present.

This one I will back off from a bit, I tend to think how the wiring HERE is done. The SPDs you had installed in the breaker box were a very good start, leave them in. Now add a line-to-line SPD at the transformer primary.

The prosurge local supplier was afraid the 320Vac SPD may explode if put line to line 240 volts.. do you have reference it can be put line to line? I thought only line to ground.

In line 4 of the table see "MCOV (VAC/VDC)" it says (320/420). That is saying you can put 420VDC on the input continuously and the device will ignore it, that it will not conduct.

Now go to line 7, "Voltage protection rating" "VPR" this shows "<1.2kV" meaning that the maximum clamping voltage is not greater than 1200V.
That is an ASSUMPTION on your part. The manufacturer is only guaranteeing that the output is less than 1.2kV. How much equipment do you want to gamble that your assumption is more accurate than the manufacturers explicit statement?

Cheers,
Tom

That's why I want to understand the microscopic physics of MOVs. If you pass 1300vac voltage to it.. would it suppress the 1300vac to become 100 volts or would it become 1200vac? Understanding the microphysics may give us a clue.. so far what have you read about this?

 

[kiki_danc]

Thanks for this info. In my country, most electrician never connect metallic chassic to ground. They just cut the ground wire.. and before this week I didn't know the purpose was to trip the breaker in case line touches metallic chassic and not electrocute the person (most electricians ignore this). From now on. I'll ensure all metallic chassic is grounded.. we never did it before. Even the refrigerator in my house and aircon are not grounded at present.
The prosurge local supplier was afraid the 320Vac SPD may explode if put line to line 240 volts.. do you have reference it can be put line to line? I thought only line to ground.
That's why I want to understand the microscopic physics of MOVs. If you pass 1300vac voltage to it.. would it suppress the 1300vac to become 100 volts or would it become 1200vac? Understanding the microphysics may give us a clue.. so far what have you read about this?

Btw.. I assume you understand the difference between VPR and SVR (Suppressed Voltage Rating). Here is a brief summary in my own words. VPR is a UL 1449 Third Edition term, UL 1449 Second edition uses SVR (Suppressed Voltage Rating).
SVR is measured using surge pulse of 6000 volts, 500 ampere and 8/20 microsecond. The SVR output is about 400 volts. In UL 1449 third edition, they use surge pulse of 6000 volts, higher 3000 ampere and 8/20 microsecond producing 1200 volts let-through. That is why in 3rd edition, the 400 became higher at 1200 Volts. This proves that 1200 volts is the not the average or ceiling but only if the input is 6000V, 3000A at 8/20 us. If the input is just 6000 volts, 500 ampere at similar 8/20 microsecond, SVR becomes mere 400 volts. So I'm assuming if the input pulse is just 1200 volts, 1000 ampere at 8/20 microsecond, the SVR/VPR would be 100 volts. This is reasonable but like you said the manufacturing didn't test it at 1200 volts, 500 ampere input. Hmm... Maybe to be safe, you have the point about using 120 volt AC.

About leaving the original as it is. Remember the 320Vac Mcov gets added twice to become 640 Vac (from 220 ac line to line).. so it starts to clamp at 640 Vac. Shouldn't I use 150 Vac Mcov instead? If it clamps at 640 Vac.. VPR or SVR would increase too... why do you say retain it... you are relying on the secondary 120 volts to lower it?

 

[kiki_danc]

Yes, the Red looks to be the long-lost third wire. And the diagram in post #85 is similar to what I suspected when you said only 2 wires, I just wasn't familiar with the Open Delta configuration. (I learned something new. GREAT!)

I looked carefully a while ago. It's really only 2 lines coming from high tension, the 3rd line is not connected. See:

It's a unique open delta with only 2 wires coming from high tension, the third wire supposed use ground (perhaps this is why we got shock from touching nails embedded in concrete inside the building??) Here are the illustration, explanations and discussions:

https://www.practicalmachinist.com/...nd-vfd/three-phase-only-two-wires-wtf-103191/
​

"Around here, many farms and other low-demand users of three phase get an arrangement called "open delta".

The utility provides two of the three phases using two hot wires and a ground. Two transformers are used, usually one larger one (typically 25 or 50 KVA), and one smaller one (typically 5 or 10 KVA).

The larger transformer has the secondary center tapped, and this tap is grounded. Let's call the ends of the secondary phase "A" and Phase "C". One end of the secondary of the smaller transformer is then tied to phase "A", with the other end of the small transformer secondary being phase "B".

At the panel, the user gets two legs 120 volts neutral to ground (Phase A and Phase C), and one "wild leg" (Phase B) which is 208 volts neutral to ground. All the 120 volt single phase loads are tapped off phase A and Phase C (hence the use of a larger transformer for those two). Usually any 240 volt single phase loads will also go from phase A to phase C as well. You can use normal three phase panels, but you have to identify the "wild leg" wires with an orange stripe at each point.

All three legs are used to provide 240 volts three-phase to the three phase loads on the site.

Overhead high-voltage lines on farms are usually bare ACSR (aluminum conductor with steel reinforcement), not copper. It is usual to run a hot line and a ground for single phase, or two hot lines and a ground for open-delta three phase.

Underground high-voltage is typically supplied with a fancy coaxial cable, with the center conductor supplying the high volts and the shield grounded. Two of these, connected to two transformers, could definitely supply you with three phase. "

But I still don't comprehend why you won't supply 120V thru a transformer to the 24VDC supply. The 240V SPDs won't keep the spikes below the 300V input rating of the supply. That was a limitation you stated earlier in the thread. Can you explain?

Cheers,
Tom

 

[kiki_danc]

No it won't. It will be suppressed to between 420V and 1200V per the datasheet you supplied in post #52 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-3#post-6063218) or between 420V and 2000V per the datasheet you supplied in post #26 (https://www.physicsforums.com/threads/surge-protector-specs.955697/page-2#post-6060374)

Ideally, the most protection is to use 3 MOVs at the primary and 3 at the load. This will catch both common mode and line-to-line surges.

View attachment 231464

About your figure above where the MOV is put line to line. I think not all SPDs can do that. For example, the specs of Prosurge has the following table:

You see. There is no L-L (Line to Line). It's only L-N, L-G, N-G protection modes listed. I think Prosurge is made in china. I'm looking for one made in USA. So in your work hope you can see what brand is the best your engineering crew has encountered. Right now I saw this good model at amazon.https://www.amazon.com/gp/product/B013WINLIO/?tag=pfamazon01-20 It can handle line to line.

So I hope you or others can share some good models too. So we can be sure to get the best. Thanks.

Then do the same at the primary using 240Vac MOVs. Of course you can use pre-built SPDs.

By the way, decide what you want to happen when an SPD fails shorted.

• Shut off power to the load when they fail, thereby protecting it from further surges.
• Disconnect the MOVs from the circuit while keeping power to the load, but they no longer protect the load.

When most SPDs fail they fail shorted, and will trip the circuit breaker feeding them to remove power.
The one you showed in post #52 is the second option, it keeps power to the load and blows an internal fuse to disconnect a shorted MOV.

You need a fuse or circuit breaker in the power feed to the SPD for the first option.
But don't try to add an external fuse to get the effect of the second option. The fuse sizing and design is a science in itself. Let the manufacturer do it.

Can we put this project to bed yet?

Cheers,
Tom

 

[kiki_danc]

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?

Everything you mentioned yesterday finally sinked in. So let's wrap up by the following questions I need to know.

1. In the US, your equipment is connected Line to Neutral and since Neutral is connected to your Ground at service entrance, then all you need are common mode SPD and not really normal mode, isn't it? (but I seem to see specs that line to neutral is called normal mode.. does it mean in the US you need to put line to line SPDs in addition to line to ground SPDs too?? In other words, is Line to Neutral also considered as Line-to-Line, why? If yes, then how about if you are connecting 120v to 120v to get 240v, then it's called Normal Mode II or Line to Line II since you already have one Line to Line if you consider Line to Neutral as Line to Line? And you will get 3 sets of SPDs in equipment in your country?

In our country. Our power is bonafide line to line, so we need normal mode (or L-L) spd. About the common mode SPD, you are saying above that equipment connected to ground won't get damaged even by 6000V strike but the concern is only the person standing nearby. Hence, if my equipments are located in isolated place without people nearby.. then I can just put one 320V Line to Line at primary side of transformer and one 150Vac Line to Line at secondary side of transformers without needing to put any Line to Ground SPDs. Is this correct?

Or did you mean that if a chassis to ground is exposed to 6000V surge, the surge can still fly to the circuit? If it only concerns protection none-existing people then I'd save 4 pieces of SPDs connecting line to ground by just using 2 line to line SPDs at primary and secondary..

2. When you have a 6000V surge at the primary side of the transformer, would it become 3000V surge at the secondary side of the step down transformer (220V to 110V)? But because there is big impedance in the transformer, I guess the surge can become 8000V.. have you thought of this? So the benefit of using transformer is just so as to use lower voltage SPD to get lower clamping voltage right?

3. I think tapping just line to ground to get 120 volts is the fastest way. I'd only need to do it for one breaker at a minor panel (not the main panel). I may be able to convince city hall I won't buy appliance in the US because many local appliance now offers 120 volts. However, I'm now very concerned of my unique 2 transformer open delta which connects to 2 primary phases and not 3 with the third one something to do with ground (as detailed in 2 messages prior to this). Is my ground contaminated? Won't this affect my connecting line to ground to get 120 volts without needing transfomers?

4. Those are the important questions for now that I need to know to decide best course of actions (I have to decide by today so we don't have to continue discussing and wasting your previous time). Anyway In my country, the supplier earns 5 times the actual cost of the unit abroad. This is because of the scarcity of SPDs in my country and SPDs seem to be very good business opportunity. Maybe let's be business partners for this, Tom... Lol.. Thanks :)

This one I will back off from a bit, I tend to think how the wiring HERE is done. The SPDs you had installed in the breaker box were a very good start, leave them in. Now add a line-to-line SPD at the transformer primary.In line 4 of the table see "MCOV (VAC/VDC)" it says (320/420). That is saying you can put 420VDC on the input continuously and the device will ignore it, that it will not conduct.

Now go to line 7, "Voltage protection rating" "VPR" this shows "<1.2kV" meaning that the maximum clamping voltage is not greater than 1200V.
That is an ASSUMPTION on your part. The manufacturer is only guaranteeing that the output is less than 1.2kV. How much equipment do you want to gamble that your assumption is more accurate than the manufacturers explicit statement?

Cheers,
Tom

 

[kiki_danc]

I've been searching for almost half day for this important information opening and reading dozens of pages but can't seem to find the definite answer and it's literally giving me headaches so hope we can discuss the microphysics of MOVs. As you can see. Most information gives illustration of SPDs being connected with ground at one terminal. This is because in the US, line to line of 240 volts is seldom use. Hence you always see this illustration even in brochures and technical paper.

What would happen if you connect any SPD line to line? For example.. in the US, if per phase you had 60 volts giving line to line of 120 volts, if you connect any regular 150Vac SPD line to line.. would it still work or does SPD needs to have one terminal at ground? What I want to know is.. do line to line SPDs need to be specially constructed? What do you think?

In the two siemens products at amazon. Even though there is L-L. It's not directly connected.. only their more expensive product has discrete L-L but with dedicated panel so you can't buy these separately. Full details at https://w3.usa.siemens.com/powerdis...alog/Documents/2017/SF-17-Sect-10-ALL-web.pdf

The only available SPDs now that you can put Line to Line is the normal SPDs. So would the MOV element function the same if it has line on both terminal compared to only one? After googling for 5 hours. I gave up looking for answer in the net. Theoretically what do you think? (if Line to Ground can be omitted as I asked in my separate message (hope you can answer it there). Then I'd just focus on L-L connection using my existing 2 pieces 320Vac SPD and putting them at line to line at breaker and near equipment for temporary solution while awaiting the 150Vac (if the supplier still decided to give it to me free after I convinced them clamping voltage can increase as you verified).

Btw.. about why my neutral or ground has current and we get slight jolt when we touch concrete with screws.. I think it' because of unbalanced 3 phase (the other owners in building don't want to balance load).. I read this at wiki's section on "ground and neutral".

"In a three-phase linear circuit with three identical resistive or reactive loads, the neutral carries no current. The neutral carries current if the loads on each phase are not identical. In some jurisdictions, the neutral is allowed to be reduced in size if no unbalanced current flow is expected. If the neutral is smaller than the phase conductors, it can be overloaded if a large unbalanced load occurs. "

After getting reply to this and the two messages above. Let's wrap up this thread as it's already time consuming and very long. And I'll give you double Like or 5 stars if there is such. Thanks a lot Tom!

 

[Tom.G]

1. In the US, your equipment is connected Line to Neutral and since Neutral is connected to your Ground at service entrance, then all you need are common mode SPD and not really normal mode, isn't it? (but I seem to see specs that line to neutral is called normal mode.. does it mean in the US you need to put line to line SPDs in addition to line to ground SPDs too?? In other words, is Line to Neutral also considered as Line-to-Line, why? If yes, then how about if you are connecting 120v to 120v to get 240v, then it's called Normal Mode II or Line to Line II since you already have one Line to Line if you consider Line to Neutral as Line to Line? And you will get 3 sets of SPDs in equipment in your country?

The philosophy seems to be to "cover all possibilities" as to how many and where the MOVs are connected. If all possible connections are made in the SPD then all the wires are at (nearly) the same voltage during a surge and the possibility of damage is reduced. As one example, if there are two or more SPDs that may be using a common Neutral (or a common Ground), then one of them may suppress a surge, causing the Neutral (or Ground) wire to momentarily rise by a few hundred volts. Another SPD on the circuit would sees this, and one or more of its MOVs will conduct to keep all the wires it is connected to at the appropriate relative voltages. Note that the supply wires at this second device may rise by a few hundred volts in this case, but the voltage difference between them will remain relatively constant, and will track the rise on the Neutral (or Ground) wire.

Hence, if my equipments are located in isolated place without people nearby.. then I can just put one 320V Line to Line at primary side of transformer and one 150Vac Line to Line at secondary side of transformers without needing to put any Line to Ground SPDs. Is this correct?

Well, not quite. Consider a Common Mode surge on the transformer primary. Because the primary and secondary winding are close to each other (often the primary will be wound right on top of the secondary) the is capacitive coupling between the two windings, just as if you put a small value capacitor from the primary to the secondary. The secondary, if it is not grounded, could then rise to the same voltage as the primary Common Mode surge. That's why power wiring, even from a transformer secondary on a power pole, has one wire grounded. (Sometimes, when a transformer fails, the primary shorts to the secondary. For instance you wouldn't want the 4kv to 16kV on the power pole transformer on your 240V service.)

Getting a shock when touching a Ground wire and a concrete wall means that one of them is connected to a hot wire somewhere! I would vote that your "Ground" is not really a Ground. Something is (dangerously) mis-wired somewhere. The "unbalanced 3 phase" and Neutral current is based on a 3-phase 4-wire configuration, 3-phase Wye connected source (120/208 or 240/416 as used in the USA).

3. I think tapping just line to ground to get 120 volts is the fastest way. I'd only need to do it for one breaker at a minor panel (not the main panel). I may be able to convince city hall I won't buy appliance in the US because many local appliance now offers 120 volts. However, I'm now very concerned of my unique 2 transformer open delta which connects to 2 primary phases and not 3 with the third one something to do with ground (as detailed in 2 messages prior to this). Is my ground contaminated? Won't this affect my connecting line to ground to get 120 volts without needing transfomers?

See my comment above.

Considering that the rest of your wiring is 'unknown' (reference 'Its 3 wire', 'no, it's only 2 wire', 'maybe the 3rd wire is ground', 'I get a shock when touching the Ground wire and the concrete wall' ), your best bet is a 240/120 transformer. If you can find an actual, confirmed Ground, connect one of the transformer secondary leads to it. That takes care of the capacitive coupling between windings. Then you can then use a 120V L-L SPD at the load. A 3 SPD on the primary side would be the safest if you have an actual Ground available.

The only available SPDs now that you can put Line to Line is the normal SPDs. So would the MOV element function the same if it has line on both terminal compared to only one?

Yes. Just be sure that if it is in a metal case that the case is not connected to one of the lead wires. The MOVs in an SPD only care about the difference in voltage between their terminals, they dont' care if say one wire has 1,000,000 volts and the other side has 1,000,100 volts; it just knows there is 100 volts across it.

The prosurge local supplier was afraid the 320Vac SPD may explode if put line to line 240 volts.. do you have reference it can be put line to line? I thought only line to ground.

Look at line 4 of the data sheet. It shows Maximum voltage. There is no minimum input voltage anywhere. And the physics of an MOV do not show any minimum either. (I think the 'local supplier' is in need of an education beyond how to take peoples money.)

Here is one link about Varistors, which is the general term for the devices in SPDs:
https://www.electronics-tutorials.ws/resistor/varistor.html
Above was found with: https://www.google.com/search?&q=how+mov+varistor+works

Here is a drawing from the above article showing the construction of a MOV.
https://www.electronics-tutorials.ws/resistor/res72.gif
The Zinc Oxide grains are close enough to each other that they are in light electrical contact, with very little current able to flow between them; probably due to the oxide layer on their surfaces. Higher voltages are able to break down this oxide layer and allow more current to flow. That's how they suppress surges, by conducting the higher voltages, usually to ground, but blocking current when only the lower normal operating voltage is present.

I've probably missed a few of your many questions, hopefully these answers covered your major issues.

Cheers,
Tom

 

[kiki_danc]

The philosophy seems to be to "cover all possibilities" as to how many and where the MOVs are connected. If all possible connections are made in the SPD then all the wires are at (nearly) the same voltage during a surge and the possibility of damage is reduced. As one example, if there are two or more SPDs that may be using a common Neutral (or a common Ground), then one of them may suppress a surge, causing the Neutral (or Ground) wire to momentarily rise by a few hundred volts. Another SPD on the circuit would sees this, and one or more of its MOVs will conduct to keep all the wires it is connected to at the appropriate relative voltages. Note that the supply wires at this second device may rise by a few hundred volts in this case, but the voltage difference between them will remain relatively constant, and will track the rise on the Neutral (or Ground) wire.Well, not quite. Consider a Common Mode surge on the transformer primary. Because the primary and secondary winding are close to each other (often the primary will be wound right on top of the secondary) the is capacitive coupling between the two windings, just as if you put a small value capacitor from the primary to the secondary. The secondary, if it is not grounded, could then rise to the same voltage as the primary Common Mode surge. That's why power wiring, even from a transformer secondary on a power pole, has one wire grounded. (Sometimes, when a transformer fails, the primary shorts to the secondary. For instance you wouldn't want the 4kv to 16kV on the power pole transformer on your 240V service.)

While waiting for my free 150Vac MOVs from prosurge.. I can wire them one 320Vac at breaker line to line and one 320 Vac at load line to line.. I'd try transformers when the 150Vac arrive. So if I'll not use transformers.. the equipments won't be damaged by surge from line to ground but only affecting person that may be near it?

Getting a shock when touching a Ground wire and a concrete wall means that one of them is connected to a hot wire somewhere! I would vote that your "Ground" is not really a Ground. Something is (dangerously) mis-wired somewhere. The "unbalanced 3 phase" and Neutral current is based on a 3-phase 4-wire configuration, 3-phase Wye connected source (120/208 or 240/416 as used in the USA).

The ground in my main breakers are really neutral wires connecting directly to the transformers. We don't have separate ground wires. Now I don't think the hot wire is connected to the concrete or neutral because it can spark immediately. It's not all the time.. sometimes only.. so I wonder if open delta unbalance loads can cause the neutral to have current too?

See my comment above.

Considering that the rest of your wiring is 'unknown' (reference 'Its 3 wire', 'no, it's only 2 wire', 'maybe the 3rd wire is ground', 'I get a shock when touching the Ground wire and the concrete wall' ), your best bet is a 240/120 transformer. If you can find an actual, confirmed Ground, connect one of the transformer secondary leads to it. That takes care of the capacitive coupling between windings. Then you can then use a 120V L-L SPD at the load. A 3 SPD on the primary side would be the safest if you have an actual Ground available.Yes. Just be sure that if it is in a metal case that the case is not connected to one of the lead wires. The MOVs in an SPD only care about the difference in voltage between their terminals, they dont' care if say one wire has 1,000,000 volts and the other side has 1,000,100 volts; it just knows there is 100 volts across it. Look at line 4 of the data sheet. It shows Maximum voltage. There is no minimum input voltage anywhere. And the physics of an MOV do not show any minimum either. (I think the 'local supplier' is in need of an education beyond how to take peoples money.)

Here is one link about Varistors, which is the general term for the devices in SPDs:
https://www.electronics-tutorials.ws/resistor/varistor.html
Above was found with: https://www.google.com/search?&q=how+mov+varistor+works

Here is a drawing from the above article showing the construction of a MOV.
https://www.electronics-tutorials.ws/resistor/res72.gif
The Zinc Oxide grains are close enough to each other that they are in light electrical contact, with very little current able to flow between them; probably due to the oxide layer on their surfaces. Higher voltages are able to break down this oxide layer and allow more current to flow. That's how they suppress surges, by conducting the higher voltages, usually to ground, but blocking current when only the lower normal operating voltage is present.

I've probably missed a few of your many questions, hopefully these answers covered your major issues.

Cheers,
Tom

You've covered so much that I am so thankful of you. Say what would happen to the MOV or SPD if it would be connected in series between live lines? I won't try this but just wanted to know what would theoretically happen?

 

[kiki_danc]

The philosophy seems to be to "cover all possibilities" as to how many and where the MOVs are connected. If all possible connections are made in the SPD then all the wires are at (nearly) the same voltage during a surge and the possibility of damage is reduced. As one example, if there are two or more SPDs that may be using a common Neutral (or a common Ground), then one of them may suppress a surge, causing the Neutral (or Ground) wire to momentarily rise by a few hundred volts. Another SPD on the circuit would sees this, and one or more of its MOVs will conduct to keep all the wires it is connected to at the appropriate relative voltages. Note that the supply wires at this second device may rise by a few hundred volts in this case, but the voltage difference between them will remain relatively constant, and will track the rise on the Neutral (or Ground) wire.Well, not quite. Consider a Common Mode surge on the transformer primary. Because the primary and secondary winding are close to each other (often the primary will be wound right on top of the secondary) the is capacitive coupling between the two windings, just as if you put a small value capacitor from the primary to the secondary. The secondary, if it is not grounded, could then rise to the same voltage as the primary Common Mode surge. That's why power wiring, even from a transformer secondary on a power pole, has one wire grounded. (Sometimes, when a transformer fails, the primary shorts to the secondary. For instance you wouldn't want the 4kv to 16kV on the power pole transformer on your 240V service.)

Getting a shock when touching a Ground wire and a concrete wall means that one of them is connected to a hot wire somewhere! I would vote that your "Ground" is not really a Ground. Something is (dangerously) mis-wired somewhere. The "unbalanced 3 phase" and Neutral current is based on a 3-phase 4-wire configuration, 3-phase Wye connected source (120/208 or 240/416 as used in the USA).See my comment above.

Considering that the rest of your wiring is 'unknown' (reference 'Its 3 wire', 'no, it's only 2 wire', 'maybe the 3rd wire is ground', 'I get a shock when touching the Ground wire and the concrete wall' ), your best bet is a 240/120 transformer. If you can find an actual, confirmed Ground, connect one of the transformer secondary leads to it. That takes care of the capacitive coupling between windings. Then you can then use a 120V L-L SPD at the load. A 3 SPD on the primary side would be the safest if you have an actual Ground available.Yes. Just be sure that if it is in a metal case that the case is not connected to one of the lead wires. The MOVs in an SPD only care about the difference in voltage between their terminals, they dont' care if say one wire has 1,000,000 volts and the other side has 1,000,100 volts; it just knows there is 100 volts across it. Look at line 4 of the data sheet. It shows Maximum voltage. There is no minimum input voltage anywhere. And the physics of an MOV do not show any minimum either. (I think the 'local supplier' is in need of an education beyond how to take peoples money.)

Here is one link about Varistors, which is the general term for the devices in SPDs:
https://www.electronics-tutorials.ws/resistor/varistor.html
Above was found with: https://www.google.com/search?&q=how+mov+varistor+works

Here is a drawing from the above article showing the construction of a MOV.
https://www.electronics-tutorials.ws/resistor/res72.gif
The Zinc Oxide grains are close enough to each other that they are in light electrical contact, with very little current able to flow between them; probably due to the oxide layer on their surfaces. Higher voltages are able to break down this oxide layer and allow more current to flow. That's how they suppress surges, by conducting the higher voltages, usually to ground, but blocking current when only the lower normal operating voltage is present.

I've probably missed a few of your many questions, hopefully these answers covered your major issues.

Cheers,
Tom

By the way. When the SPD is connected to ground at one end.. the current can escape to the ground during surge. But if it is connected line to line with no ground.. and it shorted.. where will the current go? The breaker may trip but how does it suppress the surge.. can the current make the MOV hot by somehow the MOV trapping the electrons in the oxide?

 

[Tom.G]

You've covered so much that I am so thankful of you. Say what would happen to the MOV or SPD if it would be connected in series between live lines? I won't try this but just wanted to know what would theoretically happen?

If you mean in series like a switch:

• If the supply voltage is below the turn-on voltage (suppression voltage) then it will act like a switch that is turned off.
• If the supply voltage is above the turn-on voltage (suppression voltage) then the load will see the supply voltage minus the suppression voltage.

Also realize that the suppression voltage increases somewhat as the current thru the MOV increases.
You could probably get away with trying this using a very small load like a 25W light bulb. The MOV will be thermally limited in continuous use like this so be careful it doesn't get too hot.

 

[Tom.G]

By the way. When the SPD is connected to ground at one end.. the current can escape to the ground during surge. But if it is connected line to line with no ground.. and it shorted.. where will the current go? The breaker may trip but how does it suppress the surge.. can the current make the MOV hot by somehow the MOV trapping the electrons in the oxide?

A Normal mode (L-L) surge will be suppressed by the MOV acting like a rather poor wire but shorting the lines together enough to load down the voltage surge due to the impedance of the wires; which is its normal usage.

If it is a Common mode surge, the MOV will have no effect and the voltage on both wires will rise by whatever the surge voltage is.

 

[kiki_danc]

A Normal mode (L-L) surge will be suppressed by the MOV acting like a rather poor wire but shorting the lines together enough to load down the voltage surge due to the impedance of the wires; which is its normal usage.

If it is a Common mode surge, the MOV will have no effect and the voltage on both wires will rise by whatever the surge voltage is.

Most configuration uses common mode where the MOV is connected to ground.. when there is surge.. it will short circuit.. decreasing the voltage.. why did you say the MOV will have no effect, in what context?

By the way I wonder how you know so much about SPDs.. have you worked in the industry before or are all scientists (like Witten) familiar with it?

 

[Tom.G]

in what context?

In the context of the question you asked, connected L-L.

 

[kiki_danc]

In the context of the question you asked, connected L-L.

Ah ok. Now that ties up the loose ends (pun intended)…

Thanks 10^137 Tom :)

 

[kiki_danc]

I let electrician connect the spd 320 line to line to the 220 volts line at breaker.. so far it didnt smoke hurray.. btw isn't it if an spd fails. It would short so can this trip the breaker and no adverse effect.on the equipment?

And. I forgot to ask two other things. If I'd put the 320Vac SPD near equipment line to line temporary (without transformer since I am still waiting for my 150Vac SPD and I know transformer can make up for the impedance), should the 10 meters wires from breaker be maintained for the impedance or does this only work for line to ground type 3?

And lastly what would happen if I put 2 pcs of 320Vac SPDS at breaker line to line, what would be the effect of this 2 pcs for the surge as these 2 interact with the surge? Would the surge current be divided among them or VPR would increase or decrease or any unexpected adverse effect?

 

[Tom.G]

btw isn't it if an spd fails. It would short so can this trip the breaker and no adverse effect.on the equipment?

See post #98, repeated here:

By the way, decide what you want to happen when an SPD fails shorted.

• Shut off power to the load when they fail, thereby protecting it from further surges.
• Disconnect the MOVs from the circuit while keeping power to the load, but they no longer protect the load.

When most SPDs fail they fail shorted, and will trip the circuit breaker feeding them to remove power.
The one you showed in post #52 is the second option, it keeps power to the load and blows an internal fuse to disconnect a shorted MOV.

You need a fuse or circuit breaker in the power feed to the SPD for the first option.
But don't try to add an external fuse to get the effect of the second option. The fuse sizing and design is a science in itself. Let the manufacturer do it.

To expand on that, most type 3 SPDs I've seen are of the second design; they disconnect themselves while continuing to supply the load. This is especially true of those that have an indicator showing good/bad status, such as an LED that is normally lit and goes off when the MOVs have failed.

If I'd put the 320Vac SPD near equipment line to line temporary (without transformer since I am still waiting for my 150Vac SPD and I know transformer can make up for the impedance), should the 10 meters wires from breaker be maintained for the impedance or does this only work for line to ground type 3?

If it is a type 3, yes; doesn't matter what the internal configuration is.

And lastly what would happen if I put 2 pcs of 320Vac SPDS at breaker line to line, what would be the effect of this 2 pcs for the surge as these 2 interact with the surge? Would the surge current be divided among them or VPR would increase or decrease or any unexpected adverse effect?

Surge will be divided between them, VPR will decrease, no adverse effects. (except to your wallet if you don't have an extra laying around)

Cheers,
Tom

 

[kiki_danc]

See post #98, repeated here:

To expand on that, most type 3 SPDs I've seen are of the second design; they disconnect themselves while continuing to supply the load. This is especially true of those that have an indicator showing good/bad status, such as an LED that is normally lit and goes off when the MOVs have failed.If it is a type 3, yes; doesn't matter what the internal configuration is.Surge will be divided between them, VPR will decrease, no adverse effects. (except to your wallet if you don't have an extra laying around)

Cheers,
Tom

But if you put 2 SPDs at breaker panel side by side with only 1 inch wire between the 2 SPDs, there is no 10 meter wires to make the impedance, how would that affect the second SPD at breaker panel. You said the SPD type 3 10 meters away need to make use of the 10 meter impedance to lower the voltage.. and in the 2 SPDs side by side at panel breaker.. won't the second SPD beside it not be able to lower the voltage (or if it can, to what degree)?