What SPD for a 230V Delta (No Neutral)

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pathfinders

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I am a non qualified consultant operating in the Philippines.
A very large american owned international company is my client. I am a foreign consultant interpretting requirements and ensuring thigns are done propperly.
They have a site requirement of 150 KVA. Almost everything is specified out to the model number, however their documentation on required SPD is looking at WYE 3 phase system, without specifiying voltages.
So, we are intending to supply their equipment with 3 individual sets of single phase at 50 KVA each, ehere they all come from one 3 phase 3 pole main breaker supplied fomr a banked 3 phase delta set of transfomers. So thats 11 KV WYE into 3 individual 50kva singel phase transformers wired up in WYE-DELTA with absolutely no neutral on the low voltage side. Thats 3 conductors from the trasnformer to the main breaker, each 230V between each other.
This main breaker will have a 3 pole branch dedicated for a 3 pole surge protector.
Now, the question that no electrical engineer is able to make me feel comfortable about...
what should the rated voltage on an SPD be for this setup?
Each conductor would be about 110V to ground. so therefore, my brian tells me that i need a 3 pole 3 phase , but it needs to be reated to somethign close to 120 volts.
Am I correct?
If so, i cant seem to find such a device that has the specs i feel comfortable with. They seem sto suggest such a thing is onnly for a 110 votls system, which this is not, its a 230V delta. So what dose one look for?
Im not happy wtih the local explanations, everything just sets on fire here because no one realy knows their sciences or questions their knowledge.
 
Up until this moment, i thought we were safe in specifiying this type 2 SPD: the Eaton AGDN24030R
But, I just cant understand how a 240 volt single phase SPD with a L and N input , where its differential for triggering the MOV would be approx 230V form line to ground, could have the same voltage rating for the situation where the 230 volts is generated from the differnce between phases, as opposed to phase to neutral.
For delta, line to ground is not the same as Line to neutral, becasue there is no neutral.
 
If you have a 3 wire delta there is only two choices

ungrounded - which has no ground reference and line to ground voltages could end up being anything depending on conditions, capacitive effects will have impact on the readings, but should there be a ground fault on one line it effectively becomes a corner ground system at that point.

corner grounded - which makes the other two lines 230 volts to ground so your surge protector should be designed for 230 to ground to be the normal voltage.
 
yes, its ungrounded, so what voltage do i want to see written on the MCOV data? 230v (representative of Line to Line) or 130V (representative of Line to ground)
Its always about 110 volts.
DO i perhaps not want to shunt to ground at all?
Do i in fact just want to clamp all lines together, with just a differential mode action only??
Ive never seen such an SPD, even though i se a lot of diagrams showing each line clamps to ground and 2 of the 3 clamped together.
 
beg your pardon, i just found out it is in fact one of the center outputs of one of the transofrmers is ground tapped, so its a center tapped delta.
so in that case,
Do I want a 3 pole SPD that will start clamping (MCOV) at 130 volts plus tolerance, or 230 volts plus tolerance??
After reading countless articles from industry experts, i find myself dissagreeeing with all manufacturers data sheets.
I think i have a 230V delta, which neads a MCOV 180V, so therefore, an SPD rated at 180 volts not 230.
1701320101036.png
 
Your red line on that lightning arrester chart is showing you have selected 230 KV, not 230 V!
 
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basically im seeing a massive disconnect between big companies, and proffesional individuals, advertising their expertise, suggesting that .. and i quote.
"Hence MCOV of the installed arrester must be equal to or higher than the continuous voltage between the phase and earth."
I have a suspicion that proffessional individuals are looking at MCOV and picking the most sensibel rules, that is, the voltage differnece between what is being proetected and physical earth.
Whereas large companies just dont want any risk of an early failure and associated complaint, so they that its about line to line or line to neutral, or FULL SYSTEM VOTLAGE, whatever that means.
I just want to know, what is MCOV actualyl supposed to represent? is it the voltage between each side of the MOV? if so, then I am rgiht and all manufacturers are wrongly pointing custoemrs towards oversized MCOVs.in my case, i suspect a 230 V MCOV wouldnt trigger and clamp early enough because the transient spike might only make it to the MCOV value of 230v once the actual line to line votlage is already up closure to 400 volts.
Maybe it simply doesnt matte rbecuase these transients are supposed to be thousands ov volts, but what if i actually want to clamp it propperly, at the correct votlage and fitler it to only let through the correct frikn power?
 
if it really is about voltage between lines, thats is phyiscally impossible.
The DIN rail monunted SPD i have in my hands, has absolutley no connection between the input terminals, other than the earth side which is only in the equation during an overvoltage when the MOV is actually clampin and conductive to connect the earth sdie to the input side.
So, the voltage could have nothing to do with Line to Line.
 
pathfinders said:
beg your pardon, i just found out it is in fact one of the center outputs of one of the transofrmers is ground tapped, so its a center tapped delta.
so in that case,
Do I want a 3 pole SPD that will start clamping (MCOV) at 130 volts plus tolerance, or 230 volts plus tolerance??
After reading countless articles from industry experts, i find myself dissagreeeing with all manufacturers data sheets.
I think i have a 230V delta, which neads a MCOV 180V, so therefore, an SPD rated at 180 volts not 230.
View attachment 2568823
Click to expand...
That would have to be three phase four wire then but being center tap of one phase of a delta makes the opposite corner of the delta a high leg of 1.732 times the voltage of other two corners to this grounded conductor. If your line to line volts is 230 then this high leg will be about 199 to the grounded conductor. You can't use the same surge protector that you would use on a wye system with equal voltages to ground on all three phases, it would burn out the MOV on the high leg if it were sized to closely to the 115 volts to ground on the other two lines.

BTW your chart here is all KV ranges so this 230 volt system is not covered by this chart.
 
ok so, all the utility company provides to the cable entance, is 3 wires. 3 hots, 230 volts apart.
Then , the building distributes that among the buildings tenants in individual 3 phase panels where each branch is just 2 pole single phase.Then of course there is the ground.
So, what do i choose as an SPD for this system if i want to protect all 3 phases?
Chat gpt, and quora, and that other guy all suggest that i am correct that the rating has nothign to do with the system voltage, its about the voltage between live and ground. which for me, as i have measured at my office, is about 114 volts line to ground, 240V line to line.

Now, i understand about the kilovolt ttable thing, but, surely, the same rules apply? hes suggesting that a delta system needs just the single phase portion of the three phase line to line voltage, plus some amount of buffer percentage .
I think it still aplies to 230 V, just signore the "k"... no?
 
I think ive confused things again. One of the transformers has a smaller conductor on the center tap, and that goes to , i think the system neutral or straight down the pole to ground. There is no high current carrying conductor from the high leg (dog leg) in to the sites main panel. So maybe thats not high leg, it just seems like that means it would always depend on how good the grounding is, which in my case, is terrible... Its a limestone area.
So do i need to go get 3 single phase SPDs with varying voltages for each different li e to ground, then 3 more from each line to line?
Itll be on a 40a breaker, c curve
 
You are designing protection for a country that apparently doesn't use American systems.

The IEEE chart you posted is for KiloVolts, so it is not applicable to your transformer low voltage secondary.

You need to find how your transformers are actually wired. Don't confuse transformer enclosure/tank ground connections with those of the delivered power.

Low voltage surge protectors are easy to select and size. The manufacturers typically build them in only one or two versions, for installation at the service entrance or at an interior panel fed from the main panel. They are selected based on the maximum line-line voltage, the maximum Line-Neutral voltage (if available), and finally the line-ground voltage.

Have you looked at what manufacturers offer in your voltage range?
This is a link to selection help from Schneider Electric.
 
oh, sorry is this an american only forum? ooops.
Why doesnt it say "Authentic Intelligence for North American Electrical proffesionals"? haha
This is the internet and this is a .com site.
Anyway.
I understand enough about this to know that the client is asking for type 2 only.
What im not clear on, is, what does the MCOV actuall represent? is it tested as the continuous operating voltage from input ( L) to output ( earth) or is it an estimate based on what input and earth should be for a particulare systym operating votlage?
I don tthink anyone actaully understands what im asking, or perhaps im not using industry accepted terms so im not getting the response im looking for.
If I dropped the name of the client and broke my NDA, id have people beinding over backwards to help, but I just cant. Richest man in the world.
 
No it is not American only, but 99% of the response from here are probably assuming the installation will be using a North American distribution system and be based on the NFPA 70. We also have a group that is targeted for Canadian installations.

The MCOV is the nominal maximum over voltage for that type of power system.
All arrestors experience L-G voltage and need to be rated for such. Only arrestors that offer L-N neutral protection need that rating. LV arrestor are not typically applied based on MCOV as it is not really a concern.

Is your installation going to be using an American 120/240V 1 phase 3 wire system, a 240/120V 3 phase 4wire, or something else?
 
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Something else.
3 phase Delta, 4 wire to the main panel but the neutral just goes straight down the service entrance into the dirt.
So from the main panel, its a 3 wire 230V delta.
A typical transformer installation looks like this: you will see the center of one of the transformers has a very small conductor which gives the whole thing a ground refference.
1701762536313.png
1701762550518.png
 
pathfinders said:
Something else.
3 phase Delta, 4 wire to the main panel but the neutral just goes straight down the service entrance into the dirt.
So from the main panel, its a 3 wire 230V delta.
A typical transformer installation looks like this: you will see the center of one of the transformers has a very small conductor which gives the whole thing a ground refference.
Click to expand...
Good point.
But this is not a concern when selecting surge protective device per the OP. the SPD need s to be selected to provide L-L and L-G, and maybe L-N modes of protection at the maximum nominal L-L voltages.
 
pathfinders said:
Something else.
3 phase Delta, 4 wire to the main panel but the neutral just goes straight down the service entrance into the dirt.
So from the main panel, its a 3 wire 230V delta.
A typical transformer installation looks like this: you will see the center of one of the transformers has a very small conductor which gives the whole thing a ground refference.
View attachment 2568889
View attachment 2568890
Click to expand...
If it is grounded at midpoint of one phase you should have a high leg on the opposite corner of the delta.

NEC which is the standard for the US will require bringing the grounded conductor to the service disconnect. Can't depend on earth as a fault clearing path as it generally will have too much resistance. I could see other places allowing that though but likely would require RCD's to detect a fault.
 
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