Voltage Ratings: 110/115/120, 220/230/240 or 440/460/480

[jim dungar]

Unless it was a “6 wire” system where all of the center points were ungrounded....

We don't see these systems because the NEC has required grounding if 120V is available for several decades.

 

[wwhitney]

We don't see these systems because the NEC has required grounding if 120V is available for several decades.

But 250.20(B) would allow such a system to be ungrounded. The only grounding requirements it has are for systems where there's a conductor <= 150V to all the other conductors, or for the two most common 3-phase 4-wire systems.

Cheers, Wayne

 

[jim dungar]

But 250.20(B) would allow such a system to be ungrounded. The only grounding requirements it has are for systems where there's a conductor <= 150V to all the other conductors, or for the two most common 3-phase 4-wire systems.

Cheers, Wayne

A standard high leg delta does not have <= 150V on all of its ungrounded conductors, yet it is required to be grounded.

 

[wwhitney]

A standard high leg delta does not have <= 150V on all of its ungrounded conductors, yet it is required to be grounded.

Correct, by 250.20(B)(3), which applies only to "3 phase, 4-wire delta" systems. Add a 5th (or 6th) wire, and 250.20(B)(3) no longer requires the system to be grounded.

Cheers, Wayne

 

[Jraef]

Oh well, this is kind of like this new argument about whether there were people of color in Middle Earth… it doesn’t exist so it really doesn’t matter what anyone thinks.

I for one apologize for having fed into this divergence. As was already said, there is no 240/120 3 phase 4 wire with 3 separate 120V circuits available, nor would/could there be a 6 wire version for numerous reasons, outside of some phantasy realm.

 

[drcampbell]

... you certainly can create a "240/120 4-wire [system] that has three 120-volt-to-ground legs with no stinger," it just won't be a delta. If the primary is 3-phase, just add another phase to a 120/240V 3-wire secondary system, at some angle to the single phase already present. 60/120 degrees would be easy to do with two transformers. Or you could get 4 wires out of the usual 5 wire 240/120V 2-phase system.

Cheers, Wayne

Just because you can, doesn't mean you should. I could make stop-action slow-motion videos of bonsai trees, but I don't.

 

[Besoeker3]

I'm glad we have a much simpler system in UK...................!!!!!

 

[tortuga]

I did a lot of remote cellular telephone equipment shelters in Argentina. Some of those shelters has to be located at the local telephone exchanges. I found that they used all 220 volt tools and appliances, their neutral conductors were blue...

Light blue has become the most common neutral conductor in the world. The NEC has had to allow that color for neutrals in flexible cord.

Oh and there are some third world countries with 127v power, derived from 220Y/127

Yeah not just some, all of South America, its an interesting story, that I'd like to know more about, there were competing standards and for a time they were going with US standards and 208Y/ 120 then they notched it up to 220Y/ 127.

 

[garbo]

Side note: For years a lot of people called 460 & 480 volts 440 due guess it was faster to say. Anyway while working in a large plant back in the early 80's the engineer in charge of ordering & installation of a state of the art ten millon dollar machine told the European company that we had 440 volts. The 480 volts that we had was closer to 495 volts at night causing one of the computers to trip out due to high voltage on a 24 volt power supply. He spent over 3 grand to have a 440 to 480 volt transformer air freighted to location. Only had 3 input & 3 output wires. After wiring in only the primary measured the secondary and it was only 460 volts. Had the nerve to tell me that I do not know how to connect a three phase transformer. Called him a few choice words over the phone. Turns out he ordered the wrong transformer. Finally we had to adjust taps on 13.2 KV transformer that feed the buss duct that it was feed off of

 

[James Williams]

The input range for voltage/frequency agile power supplies is typically 100-240VAC 50-60Hz. The 100V is for Japan … Many cellphone chargers, computer power supplies, and portable medical equipment have this range. They work nearly everywhere in the world.

 

[Open Neutral]

A huge red flag if you go into a panel and see every 3rd space skipped. I've known guys to terminate a circuit, not realizing it's a high leg. Some people have never seen a high leg panel, may not have heard of it.

I never saw open delta until I was in rural Califunny.
Learned it was common for deep well pumps there.

 

[jim dungar]

I never saw open delta until I was in rural Califunny.
Learned it was common for deep well pumps there.

Do not confuse open delta as being synonymous with having a high leg.
While it may be true for POCOs it is not for customer owned sources.

 

[Besoeker3]

The input range for voltage/frequency agile power supplies is typically 100-240VAC 50-60Hz. The 100V is for Japan … Many cellphone chargers, computer power supplies, and portable medical equipment have this range. They work nearly everywhere in the world.

Yes, for residential. For industrial many of the applications we encountered were Y-configuration and some were Y + D to get extra phases. For us these were typically 1,000 kVA or upwards.

 

[NewtonLaw]

This subject comes up a LOT in this and other forums, so I thought it would be a good idea to make it a "Sticky" that can be found and referred to easily when it comes up.

There are two "standards" for voltage in North America depending on which END of the wire you are looking at; "Distribution Voltage" (also called "Service Voltage") and "Utilization Voltage", both set forth in ANSI (American National Standards Institute) Standard number C84.1, backed up by IEEE (Institute of Electrical and Electronics Engineers).

The official Distribution Voltage standard for single phase is 120 and 240V, for 3 phase it is 208, 240, 480 and 600. It has been this way since the 1930s after the REA (Rural Electrification Act) during the Great Depression went to bring electricity to farms and rural areas, because the Utilities all did what they wanted to and they didn't see enough profit in it. But because each utility was different at the time, (i.e. 110, 115, 117, 120, 125, etc. etc.), and the REA didn't want to have their service trucks carry around multiple voltage ratings, they picked a "middle ground" of 120/240V and called that the standard. It has been that way since. Later on, standards for the Utility industry came along and added that no matter what they give you, it has to be within +-5%. So for a 120V system, that is between 114V and 126V; for 240V it is 228 to 252V, etc. etc. However many of the older systems still deliver what they used to deliver, regardless of what it is officially called, so yes, there are still pockets of 110V, 220V and 440V out there.

For that reason, industry organizations for manufacturers, such as NEMA (National Electrical Manufacturers Assoc.) developed their OWN standards for the devices that use electricity, and their standard was +-10%, but based on a LOWER voltage, because there is an expected voltage drop from the Service Entrance to where the device connects. So for 120V Distribution, the Utilization voltage is 115V; for 240V it is 230V, for 208V it is 200V, for 480V it is 460V and for 600V it is 575V.

So how that works out is that a MOTOR for example will be built for 230V, +-10%, so it can accept anything from 207 to 253, and because the Distribution Voltage is 228 to 252V, it fits right in. But also if the Utility was still putting out 220V instead of 240V, the LOW end of their range would be 220-5%, so 209V, still within the acceptable range of the Utilization standard.

People however are not swift on the change though, so LOTS of people still refer to residential as being 110/220, or 115/230 or 120/240 (inset joke from the movie "The Money Pit" where Michel Keaton says "220/221.whatever it takes..."). But OFFICIALLY, it is supposed to be 120/240V.

While we are on the subject of "officialdom"; When describing distribution systems that have more than one voltage available, there is a "convention" in the description that should be used to help avoid confusion.

• If the subject is SINGLE PHASE, the LOWER voltage is listed first, followed by the higher . So a residential single phase system is described as "120/240V".
• If the subject is THREE PHASE, the HIGHER voltage is listed first, followed by the lower. So 480/277V would be correct, 277/480V would not. This is especially important because we have 240/120V 3 phase 4 wire systems available. So by calling it 240/120V you are differentiating it as three phase, compared to 120/240V being single phase.

Note: Not all Power Utility Companies are required to supply the service voltage within +/-5%. In PA, the PAPUC follows PA Code 52, Section 57.13 b & c:
(b) Allowable voltage variation (primarily lighting). For service rendered primarily for lighting purposes, the allowable variation in voltage measured at the service terminals of the customer may not exceed, for a longer period than 1 minute in each instance, 5% above or below the standard nominal service voltage and a total variation from minimum to maximum of 8% during normal system operation.

(c) Allowable voltage variation (primarily power). For service rendered primarily for power purposes, the allowable variation in voltage measured at the service terminals of the customer may not exceed, for a longer period than 1 minute in each instance, 10% above or below the standard nominal service voltage during normal system operation.

 

[Hv&Lv]

Note: Not all Power Utility Companies are required to supply the service voltage within +/-5%. In PA, the PAPUC follows PA Code 52, Section 57.13 b & c:
(b) Allowable voltage variation (primarily lighting). For service rendered primarily for lighting purposes, the allowable variation in voltage measured at the service terminals of the customer may not exceed, for a longer period than 1 minute in each instance, 5% above or below the standard nominal service voltage and a total variation from minimum to maximum of 8% during normal system operation.

(c) Allowable voltage variation (primarily power). For service rendered primarily for power purposes, the allowable variation in voltage measured at the service terminals of the customer may not exceed, for a longer period than 1 minute in each instance, 10% above or below the standard nominal service voltage during normal system operation.

ANSI C84.1 ELECTRIC POWER SYSTEMS AND EQUIPMENT - VOLTAGE RANGES

ANSI C84.1 is the American National Standard for Electric Power Systems and Equipment – Voltage Ratings (60 Hertz). In 1954, the first vers...

www.powerqualityworld.com

 

[NewtonLaw]

ANSI C84.1 ELECTRIC POWER SYSTEMS AND EQUIPMENT - VOLTAGE RANGES

ANSI C84.1 is the American National Standard for Electric Power Systems and Equipment – Voltage Ratings (60 Hertz). In 1954, the first vers...

www.powerqualityworld.com

Yes, a standard, not the law.

 

[Hv&Lv]

Yes, a standard, not the law.

Kind of like the NESC. Not law but let something happen.
A lawyer in court will bring that standard up EVERY time..
Jurors like standards for POCOs to follow, law or not.

 

[FionaZuppa]

238v, 166v, 108v, 63Hz, 49Hz.
If it works, then don't question it.

Standards fall into many categories, some have more bite than others. ISO, ANSI, UL, NEC, CEC, NEMA, on and on the list goes. Some better than others, etc.

 

[Jraef]

Andrew Tanenbaum, one of the founders of IEEE, once said,

"The nice thing about standards is that you have so many to choose from; furthermore, if you do not like any of them, you can just wait for next year's model."

 

[Open Neutral]

Andrew Tanenbaum, one of the founders of IEEE, once said,

Actually Andrew's a professor and computer scientist; he wrote Minix. He laments to some degree that his offhand quote is so famous....
He is an IEEE Fellow.
https://en.wikipedia.org/wiki/Andrew_S._Tanenbaum