690VAC distribution in USA

[robinbreak]

Hi,
I am part of a Canadian company that is possibly going to be awarded a job in New Mexico, USA.

For this particular plant, as we're in the feasibility study phase, we are considering installing both a 690VAC MCC system and a 480VAC MCC system to build a steel shop plant.

I don't like two different low-voltage systems, so I'm trying to get it simplified.

Ideally, I would like to have only 690VAC through the plant, but I've been told that 690VAC is considered Medium Voltage in US?

What would that imply from the construction point of view? And what about commissioning/operation?

Is there a simple way to get the US codebook so I can give it a look?

Thanks in advance to anyone who will take the time to answer me.

 

[jghrist]

The cutoff for the National Electric Code (NEC) is 600V and below and over 600V. Standard nominal voltages are 480V and 600V. 480V is much more common.

You can view the NEC at

https://www.nfpa.org/codes-and-stan...ds/list-of-codes-and-standards/detail?code=70

Click "Free Access". Searching and navigating the NEC with the free access is a pain in the ass.

 

[waross]

I am familiar with 480 Volts and 600 Volts in Canada. Where do we have 690 Volts?
While the dividing line between low voltage and high voltage in Canada is 750 Volts, I have never seen a system operating in the region between 600 Volts and 750 Volts.
I had assumed that the 750 Volt dividing line was so that if a 600 Volt system was operated a few percent about 600 Volts to compensate for line loss, the system would not be in technical violation of the code.
The only utilization equipment rated for 690 Volts that I am aware of is IEC, 50 Hz equipment.
Running IEC, 50 Hz equipment on 60 Hz in North America may give rise to approvals issues and to Volts per Hertz issues.
That said, mixed 480 Volt and 600 Volts systems may be found in Canada in some oil sands plants.
The plant may be all 600 Volts Except for heat tracing.
There are some 600 Volt heat trace controllers on the market, but 480 Volt heat trace controllers are much more common.
Hence the two voltages, 600 Volts for motors and lighting and 480 Volts for heat tracing.
And apart for 750 Volts being set as a limiting voltage in Canada, 600 Volts is the highest standard low voltage mentioned in the code.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[crshears]

IIRC the Illinois Central Railway tourist site uses 690 volts on their pantograph / overhead drive system; unfortunately I do not recall for certain whether this was single-phase AC or DC . . . but the unusual voltage number has stuck in my mind for years now.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[xnuke]

The cutoff for the National Electric Code (NEC) is 600V and below and over 600V

Not true, the cutoff is 1000 V, and has been for several code cycles now.

I agree with the others, no one I know uses 690 V, they use 600 V because ANSI standard voltages are integer multiples of 120. That's why the cutoff in the NEC used to be 600 V. My understanding is that it was increased to 1000 V to harmonize with IEC standards and to accommodate PV and battery system inverters that need a bare minimum voltage of 678 V DC input (and typically operate a few hundred volts higher) to be able to create 480 V AC rms.

I recommend you plan for a 600 V system.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[resqcapt19]

While the NEC is moving from 600 volts to not over 1000 volts AC and 1500 volts DC, much of the equipment and conductors are still marked for 600 volts, so a change to 690 would require different wiring methods.

 

[waross]

Teck cabe is available in both 600 Volt and 1000 Volt ratings.
Switches and other equipment not so much.

we are considering installing both a 690VAC MCC system and a 480VAC MCC

Why???
Is this a misprint?
We had a customer with a mix of 480 Volt and 600 Volt motors.
They had a 600 Volt service feeding a combined Power Distribution Center and MCC.
This was one unit, Service Entrance equipment, 600 Volt MCC and lighting and heating feeders, an internal 600/480 Volt auto-transformer and a 480 Volt MCC.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[davidbeach]

I’ve seen a bunch of 690V stuff and every single circuit runs between one inverter (type 4 wind or PV, BESS similar) and one transformer to step the 690 to 34.5kV. So seeing the availability of 690V transformers doesn’t mean there’s a general application case.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[electricuwe]

Also consider regions outside Amercia: 690 V is common in European heavy industry. That is the reason why a lot of equipment is available for this voltage class, also from US-based suppliers.

 

[LionelHutz]

Finding UL listed equipment for 690V will be a big problem if that's going to be a requirement. It's really the biggest hurdle to using 3-phase 690V. There is a fair bit of DC stuff for solar listed.

 

[Gr8blu]

In North America, there are three voltage "levels": low (< 1000 V), medium (1001 - 69000 V), and high (69001 +). These values are independent of being AC or DC. Mostly, the voltages are three-phase; the exception can be for values below 240 V.

The standard North American (i.e. US) line voltages covering most industrial equipment are: 12, 24, 120, 240, 480, 2300, 4160, 6900, 13800. Canada also sees 600 V on occasion.

690 V is a reasonably common European distribution voltage level within the industrial sphere - which is why there are a bunch of IEC breakers and other switchgear rated at that level.

Converting energy to motion for more than half a century

 

[LionelHutz]

Canada also sees 600 V on occasion.

Sure, if almost all the time is what you call occasion.

 

[Padlock01]

Hi All,
In South Africa, we use the following voltages for LV motors 50Hz 415V 525V 690V 1000V voltages above 1000V are classed as MV ie. 2,2kV 3,3kV 11kV
22kV 33kV beyond their HV then EHV.

 

[LionelHutz]

In North America, there are three voltage "levels": low (< 1000 V), medium (1001 - 69000 V), and high (69001 +).

There is a real mix of voltages ranges or limits depending on where you look.

1501V is considered the cutoff point for medium voltage contactors as per UL347 which also considers medium voltage gear as starting at 751V.

The UL508A voltage cutoff changed from 600V to 1000V with edition 3 released in 2018.

UL489 for breakers is 1000VAC and 1500VDC. I believe it was increased to 1000VAC in a fairly recent edition.

I believe the end goal is to get all the standards aligned so at least up to 1000VAC is considered low voltage.

 

[dpc]

You will regret trying to use 690 V for basic plant distribution in the US. 600 V is certainly possible. If you don't need the additional capacity, then 480 V will make your life and everyone else's involved much simpler.

 

[davidbeach]

If 480V really doesn’t get it for a plant in the US go all the way up to 2400 or 4160V. Forget the odd stuff that might exist elsewhere in the world.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[robinbreak]

Wow, didn't expect so many answers!
Thanks to everybody for their contributions.

The 690VAC has been specified by the OEM because of fairly large loads on a specific section of the plant.
Our Medium Voltage available in the plant will be 13.8kV, but I'm not sure if I want these 4 motors (450 HP, 450 HP, 350 HP, 200 HP) on a MV VFD.

I know Rockwell and Siemens provide 690VAC rated equipment (MCC, VFD, etc), but my worry is about long delivery spare parts for these components.
And transformers avialbility might also be an issue.
At this point, turning everything to 690VAC is not an ideal solution.

So it looks like:
480VAC for < 200 HP motors
690VAC for > 200 HP < 500 HP
13.8kV for > 500 HP
might be the most feasible.

 

[waross]

I know Rockwell and Siemens provide 690VAC rated equipment (MCC, VFD, etc),

690 Volt motors will probably be 50 Hz rated.
An old rule of thumb is to consider a higher voltage when the HP exceeds the voltage.
600 Volts should satisfy that adage and lots of availability out of Canada.
600 Volts, 60 Hz has been a standard voltage in Canada for over 45 years.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[LionelHutz]

You can run all of those motors on 480V. Forget the 690V and forget putting the 500hp on 13.8kV because that VFD will cost too much.

600V is prevalent in Canada, so most gear like breakers, contactors, wire etc. is rated for at least 600V and MCCs and such are reasonable easy to get in 600V version in North America. But, the US market is predominantly 480V, so 480V is the logical choice to use in the US market.

Your OEM has no clue about the USA market, so you have to educate them. Tell them it must be 480V.

 

[waross]

The old adage:
"Ignorance can be cured, stupid is forever."
In the event that the customer cannot be "cured", I suggest a cost comparison and a spares availability assessment.
For;
a) 480 Volts.
b) 480Volts plus 600 Volts.
c) 480 volts plus 2400 Volts or 4160 Volts. (motors and transformers may be 2400/4160 Volts, wye/delta and 4160 takes less copper.)
d) 480 Volts plus 690 Volts. (Motors for 690 Volts at 60 Hz may be a special order. 50 Hz motors will work, but if you show them as re-rated 50 Hz motors the customer may be more inclined to reject 690 Volts.)
Good luck.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!