690V Equipment in America

[iwire]

We had a project years back where part of the commissioning was testing the VFD bypasses on four 500 HP motors.

It worked but also got the attention of the power company who had planed around VFD start ups.
From what I heard they were kind of upset.

 

[kwired]

I don't know but if you had a 690 volt wye system the voltage from each phase to the neutral point should be 400 volts.

After some more thought I don't see why you couldn't change the operating voltage from 400 to 690 by connecting the windings in a delta configuration for the lower voltage and connecting them in wye configuration for the higher voltage.

 

[kwired]

We had a project years back where part of the commissioning was testing the VFD bypasses on four 500 HP motors.

It worked but also got the attention of the power company who had planed around VFD start ups.
From what I heard they were kind of upset.

Possibility many other power customers were upset also, and you and your crew probably had a moment where someone burst out of the silence with "OOPS", or maybe even something I can't say here

 

[weressl]

Hello Forums!

This is my first question on here!

I have a very large (2000hp+) motor that requires 690V. We are in the early design process and the motor HAS to be 690V.

It's a non-UL voltage and is sadly just above the cut-off for low voltage into medium voltage.

So it seems that I have to use all medium voltage equipment (disconnects, cabling, ext). Made worse by the fact I need to keep it shielded (going to be a very expensive cable). Do I have to use everything rated 5kV?

Is there some kind of IEC equipment that I can use?
I mean there has be equipment built for the purpose of large ampacity 690V loads, where can I get it?
Can I use this equipment in the States?
What code issues will I run into? Or do I just do everything based on voltage ranges? (For example, 600-5000v is a certain safe working clearance. However, piece of enclosure equipment {I think} that is above 600V needs to be certain size and treated like medium voltage)
Can some of the medium voltage rules be 'softened' up, or I have to design all nearly all components as if they were up too 5000V.

Thanks!

The first question should be is it 50Hz? (690V is a standard IEC voltage for 50Hz equipment but not 60Hz.) If it is re-rated to 60Hz, then your HP rating is different,\ and IEC machines are normally rated in kW though.

 

[iceworm]

First off, I can't answer a lot of your questions. I have not been involved in design with the listed constrainsts. And I do little design work. But, perhaps I have some ideas that will help.

Assumptions:
1. I'm guessing you are not the engineer-of-record, but rather one of the design team. Why does this matter? Well if so, you are not making policy decisions, but rather following directives. This is okay, it actually narrows down the options available.

2. The equipment is to be powered from a 60Hz utility connection.

3. The project is big enough that the existing plant can add a 2011Hp motor to the existing system, or if a new plant, the utility is included in the planning.

4. Project is industrial, not commercial - not open to the public, not waste water, not potable water.

... I have a very large (2000hp+) motor that requires 690V. We are in the early design process and the motor HAS to be 690V. ...

... Is there some kind of IEC equipment that I can use? ...

... What code issues will I run into? ...

As noted by others:
2000Hp at 690V really sucks.
1700A X 1.25 = 2100A
Thats a lot of copper.

As for the IEC equipment, I wouldn't worry about it. This is a non-trivial project. Your not going to cheap it out. You're going to design a safe, reliable, cost-effective system. I'd be certain that is what is what your customer wants.

Get rid of this whole idea of code issues. The NEC is a set of minimums that is not guarenteed to work well or efficiently, may not burn down, and should not shock you too easily. It is not about design, and it has very little guidance for systems above 600V. Once you meet "safe, reliable, cost-effective", any code issues are generally legal trivia.

... I don't know what type of shielding I need to be honest. I think it will not be made for VFD. It has to be very heavy duty. All I know is that we will need it. I'm kind of inexperienced in cable shielding specifications. ...

hamm -
It's time to get some help. You are not going to spec this with intenet gossip. If your design group does not have the expertise, you will have to hire it.

... Maybe the AHJ would accept a design that has your seal on it in lieu of a listing.

It's rare an AHJ has much to say about complex, high power, industrial design. They generally don't have the expertise available to judge. One exception is local requirements on listed equipment. I've worked a few jurisdiction where the AHJ insists on listings far in excess of NEC requirements. Morons or not, they have the badge and the gun - I generally say, "Yes Sir!"

... do I need to use medium voltage switchgear housing or low voltage?

These are on the accounting end (cost-effectiveness) of the design issues.

I'd probably look at taking the service at 13.8KV or 4.16KV, using either 15KV or 5KV equipment. Do the motor starting and protectiving relaying at the MV. Put a MV primary Delta/ 690V Delta transformer between the motor starter and motor, maybe 4MVA - depending on motor starting load. Probably have to put GF on the Delta secondary to watch for motor faults.

Or
Take the service at 480V, 3000A, 65KA - 100KA equipment, protective relaying at 480V, 480d/690D transformer feeding the motor, Same GF on delta secondary.

But, this is just my internet gossip - no better than anybody else's, and certainly nothing I would rely on.

ice

 

[gadfly56]

First off, I can't answer a lot of your questions. I have not been involved in design with the listed constrainsts. And I do little design work. But, perhaps I have some ideas that will help.

...It's rare an AHJ has much to say about complex, high power, industrial design. They generally don't have the expertise available to judge. One exception is local requirements on listed equipment. I've worked a few jurisdiction where the AHJ insists on listings far in excess of NEC requirements. Morons or not, they have the badge and the gun - I generally say, "Yes Sir!"...

Nassau County, NY?

 

[Jraef]

Hello Forums!

This is my first question on here!

I have a very large (2000hp+) motor that requires 690V. We are in the early design process and the motor HAS to be 690V.

It's a non-UL voltage and is sadly just above the cut-off for low voltage into medium voltage.

So it seems that I have to use all medium voltage equipment (disconnects, cabling, ext). Made worse by the fact I need to keep it shielded (going to be a very expensive cable). Do I have to use everything rated 5kV?

Is there some kind of IEC equipment that I can use?
I mean there has be equipment built for the purpose of large ampacity 690V loads, where can I get it?
Can I use this equipment in the States?
What code issues will I run into? Or do I just do everything based on voltage ranges? (For example, 600-5000v is a certain safe working clearance. However, piece of enclosure equipment {I think} that is above 600V needs to be certain size and treated like medium voltage)
Can some of the medium voltage rules be 'softened' up, or I have to design all nearly all components as if they were up too 5000V.

Thanks!

If your area requires NRTL (Nationally Recognized Testing Lab) listing of equipment, then you are screwed to be honest. UL and the NEC jump from "low voltage" (i.e. 600V and less) to "medium voltage" (i.e. 601V to 15kV), both with equipment and with cable. So once you are at 601V and up, you need medium voltage rated cable, and that will likely be shielded (there are rules withon article 390 that might allow unshielded). As mentioned above, you also generally need a Medium Voltage Splicing Certificate to work on it as an electrician in most jurisdictions.

Cable is going to be a BIG issue. One reason why people use MV is because it reduces the cable size, and because of that, MV cables are generally not as readily available in larger sizes like LV cable is. But because you are still at a "low" medium level, you are not going to see that much size reduction benefit. So 2100A is going to take a LOT of parallel MV cables per phase. If for instance you manage to find some 500kCMIL MV cable, that will take 5 cables per phase. At 2lbs per foot per cable, that is a LOT of weight to deal with if there is any distance involved. Even if you find 750kCMIL MV cable, that will mean 4/phase and 1000kCMIL doesn't buy you any further reduction, so no point.

In my opinion, someone had better get to work on finding a suitable 2200V or 4000V motor replacement, you are going to be buying the MV gear anyway and going to a real MV voltage level reduces the copper.

 

[kwired]

If your area requires NRTL (Nationally Recognized Testing Lab) listing of equipment, then you are screwed to be honest. UL and the NEC jump from "low voltage" (i.e. 600V and less) to "medium voltage" (i.e. 601V to 15kV), both with equipment and with cable. So once you are at 601V and up, you need medium voltage rated cable, and that will likely be shielded (there are rules withon article 390 that might allow unshielded). As mentioned above, you also generally need a Medium Voltage Splicing Certificate to work on it as an electrician in most jurisdictions.

Cable is going to be a BIG issue. One reason why people use MV is because it reduces the cable size, and because of that, MV cables are generally not as readily available in larger sizes like LV cable is. But because you are still at a "low" medium level, you are not going to see that much size reduction benefit. So 2100A is going to take a LOT of parallel MV cables per phase. If for instance you manage to find some 500kCMIL MV cable, that will take 5 cables per phase. At 2lbs per foot per cable, that is a LOT of weight to deal with if there is any distance involved. Even if you find 750kCMIL MV cable, that will mean 4/phase and 1000kCMIL doesn't buy you any further reduction, so no point.

In my opinion, someone had better get to work on finding a suitable 2200V or 4000V motor replacement, you are going to be buying the MV gear anyway and going to a real MV voltage level reduces the copper.

Think about how much copper is needed if they make this motor run on 208 volts

 

[weressl]

If your area requires NRTL (Nationally Recognized Testing Lab) listing of equipment, then you are screwed to be honest. UL and the NEC jump from "low voltage" (i.e. 600V and less) to "medium voltage" (i.e. 601V to 15kV), both with equipment and with cable. So once you are at 601V and up, you need medium voltage rated cable, and that will likely be shielded (there are rules withon article 390 that might allow unshielded). As mentioned above, you also generally need a Medium Voltage Splicing Certificate to work on it as an electrician in most jurisdictions.

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Cable is going to be a BIG issue. One reason why people use MV is because it reduces the cable size, and because of that, MV cables are generally not as readily available in larger sizes like LV cable is. But because you are still at a "low" medium level, you are not going to see that much size reduction benefit. So 2100A is going to take a LOT of parallel MV cables per phase. If for instance you manage to find some 500kCMIL MV cable, that will take 5 cables per phase. At 2lbs per foot per cable, that is a LOT of weight to deal with if there is any distance involved. Even if you find 750kCMIL MV cable, that will mean 4/phase and 1000kCMIL doesn't buy you any further reduction, so no point.

In my opinion, someone had better get to work on finding a suitable 2200V or 4000V motor replacement, you are going to be buying the MV gear anyway and going to a real MV voltage level reduces the copper.

There is TC, RHHW rated DLO cable available with 2000V Insulation and is perfectly suitable for this application. It an unshielded and requires no specific termination with the exception of special lugs due to the high strand count.

http://okonite.com/Product_Catalog/section7/sec7-pdfs/7-17.pdf

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Meets the RHH/RHW requirements of NEC/UL and can be labeled as such on special orders.

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