[amblin]

YES.

Best example is a computer data processing center. Normal mains power is run through a UPS system/s that has an isolation transformer/s and at the end process the neutral of the separately derived system is connected back to the main electrical service's earth grounding electrode system. The neutral is also bonded, connected, to the metal enclosure of the isolation transformer/s or first disconnecting means metal enclosure. This point is where all safety equipment grounding conductors connect to.
Microsoft does not use an "Isolated Power System" to power their Mega dollar server equipment in their data processing facilities. If an "Isolated Power System" is so great why don't they use it to power their equipment?

What are the chances you can get a wiring diagram of the unit you are having built and post it here on your thread. A picture is worth a thousand words.

Does the unit have a "Line Isolation Monitor (LIM)" that will notify the user if one of the 2 hot ungrounded floating conductors come into contact with the metal enclosure of the transformer enclosure itself or a piece of equipment that is fed from the "Isolated Power System" that has a metal enclosure. An audible alarm and or maybe a warning light?  If not how will the user know if such a fault occurs? Or does the user just wait for the other shoe to drop. That can be dangerous and or possibly expensive.

 
 

Well I believe those high value systems will have their own dedicated bullet proof power solutions way beyond the capabilities of a humble isolation transformer...Several years back we had some critical data processed by a super computing center, they had an entire underground chamber dedicated to power units including two seperate grids and industrial transformers at their disposal , an array of in house emergency generators and something I believed to be a battery based system for both processing and heat management . Last year there was a massive , massive 3KT+  magnitude chemical explosion not far from the processing center which created a huge crater several hundred meters in diameter and a widespread black out but the only damage done to them were some broken glass..


The big problem here is that the unit is still being tested at the factory, so I can't check it out in person. But from what I've learnt there is a chassis ground point visible in one of the pictures I posted, on the right side of the cabinet with a green and white connected to it .

Although I'm not sure if it's the same as the one you mentioned, but yes, they installed micro chip based safety devices on both input, output stages and the transformer itself with soft start function so if any two of the L/N wires shorts with the cabinet fries someone, or in case of a surge , overheat or any of the devices that connected to it shorts , and if there's anything wrong with the transformer itself , power will be cut for 10 minutes and lights will flash awaiting a manual reset. If not reset in time the unit will shut off . That is if the breakers (4 including PDUs)fails to trip in the first place. And there're two voltage-o-meters showing actual readings of different stages.

3 lights will lit up in sequence as the unit starts itself . Red,  yellow for input power and safety checks will lit at the same time,and then green light is good to go.

[Speedskater]

Those big IT systems are all digital, not an analog signal in the building. (all not many analog signals)

The virtue of a Separately Derived System is that the Safety Ground/Protective Earth is connected to the Neutral near the transformer. This means that noise currents, interference currents and leakage currents are have a very short path back to their voltage source. Just what is their voltage source? Why it's the transformer's Neutral connection.

By the way, the required connection to Planet Earth has nothing to do with any of this.

[jea48]

Can any one that has been following this thread regarding an "Isolated Power System", where the mains are left floating above ground, is used in any recording studio big or small?

Does any one know of an audio or video equipment manufacture that recommends their equipment be fed from an "Isolated Power System? Maybe Bryston? 

The virtue of a Separately Derived System is that the Safety Ground/Protective Earth is connected to the Neutral near the transformer. This means that noise currents, interference currents and leakage currents are have a very short path back to their voltage source. Just what is their voltage source? Why it's the transformer's Neutral connection.

Just what is their voltage source? Why it's the transformer's Neutral connection.

BINGO!
 So Mr. EE please explain to the class how that works in the case of a separately derived "Isolated Power System" where there is no neutral.

By the way, the required connection to Planet Earth has nothing to do with any of this.

On that we agree. The mother earth connection is mainly for lightning protection.

As for the ground that has been discussed in this thread, at least by me, it has been the established EG (Equipment Ground) by intentionally bonding one of the secondary leads of the separately derived power system to the transformer's metal cabinet/enclosure or the enclosure of the main disconnecting means for the new separately derived power system. Thereby the EG for the separately derived power system is established making it a Grounded Power System. The receptacle EG will connect to the EG enclosure. A ground fault circuit path is provided in the event of a ground fault..... From the source HOT ungrounded conductor >>>> through the EG conductor >>>> to the source neutral conductor.


When NEC speaks of connecting the neutral of the separately derived power system back to the main electrical service's grounding system/Grounding Electrode System, it's not just the earth connection, it's also the connection to the main electrical service neutral/EG enclosure connection at the main electrical service's equipment cabinet.
The idea is to maintain one common ground plane throughout the building/facility/structure.

[Guy 13]

How about posting an electrical diagram of the set-up ?

Guy 13

[Speedskater]

...................................
 So Mr. EE please explain to the class how that works in the case of a separately derived "Isolated Power System" where there is no neutral.

What kind of system would that be, within the NEC system? (a balanced system has a Neutral point, even if the receptacles don't)

have to run, be back later.

[amblin]

What kind of system would that be, within the NEC system? (a balanced system has a Neutral point, even if the receptacles don't)

have to run, be back later.

Indeed, while discussing with their engineer I was told there will be no L/N difference on the receptacle / output side and it's not necessary to worry about earth/ground connection. At least not necessary on an 'isolation transformer'.  Which worried me quite abit since it's common sense to double check L/N and earth.

I thought these transformers were quite common at least on the DIY market, and there're quite a few manufacturers selling similar systems such as bryston, isotek etc.  It's especially useful where in crowded cities one earth line is shared by all 22 apartments of the entire building (in my case), and sometimes up to 200+ apartments in some countries, which I believe is quite unusual in the states.

Just one example, when I set my wifi to search, usually there're several dozen results. 

[jea48]

What kind of system would that be, within the NEC system? (a balanced system has a Neutral point, even if the receptacles don't)

A balanced power system is a Grounded Power System. The center point of the single phase secondary winding is grounded. From either hot ungrounded conductor to the EG a difference of potential exists. Short either ungrounded conductor to the EG and watch the ground fault current sparks fly, until what ever overcurrent device hopefully opens the circuit breaking the ground fault.

With an Isolated Power System short out one or the other floating ungrounded conductors to the EG and what will happen? Nothing.... System will continue operate just fine. Hopefully the Unit has a Line Monitor to tell the user one Line has went to ground. So one Line is now connected/bonded/grounded to the EG. Maybe the ground fault happened in one of the Bryston Amps to the metal cabinet. (Assuming the Bryston amp has a 3 wire cord and plug.) Could be on the Line feeding the fuse. Could be on the Line feeding the other side of the power transformer. No problem though, everything will still work just fine. The Isolated Power System is Now a Grounded Power System. The Line that shorted to the cabinet of the Bryston amp is now a grounded conductor.

Now, What IF _ _ _ _ _. Fill in the blanks.

[jea48]

amblin,

Here is a brochure for Bryston Power Conditions.
Check out page #3. Note the block diagram showing the output of the unit to the duplex receptacles. Look closely at the power Lines that feed the receptacles. The top Line is the HOT conductor and connects to the hot terminal/contact. The bottom Line is the intentionally grounded conductor that becomes the neutral conductor that connects to the neutral terminal on the duplex receptacle. NOTE the neutral wire is connected to ground.

http://bryston.com/PDF/brochures/BIT_BROCHURE.pdf

The power Conditioner output is a Grounded Power System and not an Isolated Power System. And yet it provides isolation from the mains power feeding it.




Notice Bryston's Balanced Power,  power conditioner.... Bryston had the unit built to meet UL, CSA, as well as NEC safety requirements for the unit to be used by a non professional in a residential dwelling occupancy.

The secondary winding is not a split phase winding, (a single phase winding with a center tap) for making the secondary output balanced power. Instead the secondary is just a single phase winding where one leg of the output is intentionally grounded creating the neutral. Again the power conditioner is a Grounded Power system.

So why does Bryston call it a balanced isolation power conditioner? The unit is made for countries where houses are fed from a single phase, split phase winding, Utility Power Transformer. The primary winding of the Bryston  unit's power is fed with 240V, Balanced Power.    (120V 0V 120V) Line 1 to Line 2, 240V. Center tap is grounded.


 http://bryston.com/products/other/BIT15.html

Click on manual

[srb]

Now, What IF _ _ _ _ _. Fill in the blanks.

Put a sticker on the enclosure?

 

[amblin]

amblin,

Here is a brochure for Bryston Power Conditions.
Check out page #3. Note the block diagram showing the output of the unit to the duplex receptacles. Look closely at the power Lines that feed the receptacles. The top Line is the HOT conductor and connects to the hot terminal/contact. The bottom Line is the intentionally grounded conductor that becomes the neutral conductor that connects to the neutral terminal on the duplex receptacle. NOTE the neutral wire is connected to ground.

http://bryston.com/PDF/brochures/BIT_BROCHURE.pdf

The power Conditioner output is a Grounded Power System and not an Isolated Power System. And yet it provides isolation from the mains power feeding it.




Notice Bryston's Balanced Power,  power conditioner.... Bryston had the unit built to meet UL, CSA, as well as NEC safety requirements for the unit to be used by a non professional in a residential dwelling occupancy.

The secondary winding is not a split phase winding, (a single phase winding with a center tap) for making the secondary output balanced power. Instead the secondary is just a single phase winding where one leg of the output is intentionally grounded creating the neutral. Again the power conditioner is a Grounded Power system.

So why does Bryston call it a balanced isolation power conditioner? The unit is made for countries where houses are fed from a single phase, split phase winding, Utility Power Transformer. The primary winding of the Bryston  unit's power is fed with 240V, Balanced Power.    (120V 0V 120V) Line 1 to Line 2, 240V. Center tap is grounded.


 http://bryston.com/products/other/BIT15.html

Click on manual

Yeah, I've shown them the pdf since day one and continuously reminded the guy responsible that the receptacles were supposed to be grounded.

The guy said he's not sure what exactly bryston meant by a 'clean electrical ground' on the receptacle end . Because while the first stage is wired to AC mains ground (public ) by default, the second/output ground can not. Because if you do the unit will simply become two identical 'coils' both doing the same thing, the ground is still contaminated by other line users and noise/interference will travel directly to the receptacles just like a wall socket unless there's an active filtering circuit of some sort but if an active circuit is needed, the entire unit becomes pointless and a waste of materials .

So he suspect the unit in the pdf  either a) provided a seperate rod the user can put into earth dedicated to the receptacle end. Or  b) wired the second stage to a seperate chassis ground point with dedicated breaker and other secondary safety devices connected like common practice on an isolation transformer. So if LN shorts with someone or something frying ,  the beaker will immediately trip and trigger the safety measures.

[jea48]

Put a sticker on the enclosure?

 

That's not the problem. The transformer enclosure is grounded. It is connected to the EG (Equipment Ground) of the mains power "Grounded Power System" feeding it.

This may help you understand what an Isolated Power System is.
https://vam.anest.ufl.edu/simulations/orelectric.php



An Isolated Power System or IPS, as defined by Article 3.3.85 in NFPA 99
and NEC® 517.2 is, “A system comprising an isolating transformer or its
equivalent, a line isolation monitor, and its ungrounded circuit conductors”.

http://static.schneider-electric.us/docs/Electrical%20Distribution/0104DB0701.pdf

[Speedskater]

The above referenced Isolated Power System are for hospital installations. They come with a list of expensive NEC & NFPA requirements.

There are other un-grounded AC power systems. Each comes with it's own list of requirements. It's unlikely that most electricians will see any of these system in their career.

[jea48]

The above referenced Isolated Power System are for hospital installations. They come with a list of expensive NEC & NFPA requirements.

Technically it's an ungrounded power system.

There are other un-grounded AC power systems. Each comes with it's own list of requirements.

Usually 3 phase Delta or 3 phase wye ungrounded power systems. Found in the likes of Soybean processing plants, oil refineries, steel or aluminum melting foundries just to name a few.

One common thread with the isolated power system and ungrounded power systems. They employ some type of phase/Line monitor to alert the trained authorized personnel a phase/line has faulted to ground. They have some type detection system and warning to alert the personnel a Line or phase is faulting or faulted to ground. No sparks, breakers will not trip, plant continues to run. In old facilities the electricians then have the task to find the problem and correct it. Hopefully before a different phase goes to ground.

 It's unlikely that most electricians will see any of these system in their career.

You are kidding right?

//

http://www.csemag.com/single-article/choosing-between-grounded-and-ungrounded-electrical-system-designs/d12cdbc16809bc766d173d314e46f281.html?tx_ttnews%5BsViewPointer%5D=2

 http://www.powerlogic.com/literature/LineToGroundVoltageMonitoring_08262005.pdf

http://ecmweb.com/content/choosing-grounding-options-electrical-power-systems

http://bender.org/products/ground-fault-ungrounded-systems.aspx?gclid=CMSHw-etqc4CFZSCaQodpuIMGQ

[Speedskater]

Not kidding at all!
This from your first link:

Although the NEC requires the majority of electrical systems to be grounded, some are actually required to be ungrounded. There are only five different electrical power systems/subsystems noted in NEC Article 250.22 where the code committee has determined the hazards of grounding to outweigh safety benefits of grounding.

*********************************************
I wrote:
It's unlikely that most electricians will see any of these systems in their career.

Maybe see is too strong a word. As they could be in a factory with an un-grounded system. But most of the circuit that they work with are grounded.

[amblin]

Guys

The transformer just arrived and it's  running.

Unfortunately my cat damaged 14B2 is still away for repairs so I had to use my back up system, a pair of old accuphase P450, providing 200watts of juice per channel at 8ohms to my tannoy GRF memory HE.

All components connected to the transformer via an industrial socket board , all connections behind the sockets were made by thick solid OFC bars. With the exception of BP26 which is connected to a dedicated , much smaller 500w isolation transformer because for some unclear reasons the bp26 must be connected to a different power source otherwise there will be a significant gain in the right channel.

And the improvements? Well I wouldn't say 'significant ' . But in a blind 3 round random AB test with few friends each taking notes of their own, the top notes were:
1, smooth HF , softer to the ear , warm, punchy bass
2, better stereo image , instrument separation , Air.

So in the end, it's well worth the effort . I'm especially impressed by the soft start circuit , it was added to lessen the high current stress during a cold power up. The transformer would make a distinctive 'hum' during initial power up but becomes completely silent after a soft 'click' sound and the green lights lit up.

And thanks everyone for your inputs so far

A