Difference Between NEC and NESC

EmpireWind

Member
Location
Virginia
Occupation
Electrical Engineer
Hi,
I would like to ask what your thoughts are on the difference between NEC and NESC applicability.
Is NEC applicable for LV systems i.e. 1000 Volts and below? In NEC section 311.2 defines medium voltage upto 35kV but that is the only reference I found for voltages greater than 1000.
And NESC for voltages above that?
What is the voltage breakdown for LV systems, Medium voltage systems, HV and EHV?
Thanks,
FG.
 

paulengr

Senior Member
Hi,
I would like to ask what your thoughts are on the difference between NEC and NESC applicability.
Is NEC applicable for LV systems i.e. 1000 Volts and below? In NEC section 311.2 defines medium voltage upto 35kV but that is the only reference I found for voltages greater than 1000.
And NESC for voltages above that?
What is the voltage breakdown for LV systems, Medium voltage systems, HV and EHV?
Thanks,
FG.

NESC is for generation (grid based, not backup), transmission, and distribution. NEC is for utilization. Most people say NESC covers utilities while NEC is for customers but that’s not exactly the case. Utilities have offices and other utilization loads and customers with extensive generation such as paper mills often follow NESC for some areas. The line is often called the Point of Delivery (POD). This is worked out between utility and customer but with industrial plants the lines can get very blurry. In a large mine in NC they fed 7 houses from the otherwise private system due to their being mostly isolated from the utility several miles away. The facility has over 50 MW of waste heat electric generation. They are fed from a transmission line, have a 230 kV:22,900 V sub yard, and utility metering is located on site in their switch house rather than externally. They have over 70 miles of internal power distribution lines. So they follow both NESC and NEC.

NEC generally stops at 35 kV because that is medium voltage while NESC covers transmission and sub transmission voltages as well but again these are not hard rules. High voltage electrostatic precipitators and some testing equipment falls under NEC but can get up to 100 kV.

There are many differences between them. NESC is both an equipment design and construction standard and work methods. NEC covers installations but not design (covered mostly by Listjng agencies) and not work methods. NEC is highly prescriptive with detailed rules for every bit of construction while NESC is often more performance based and leaves design details to others. NEC in some form is legally required in all 50 states while NESC is a voluntary standard, not law. NESC is also an IEEE standard where NEC is an NFPA standard. That may sound similar but the two groups generally don’t get along at all. NEC especially in recent years has been captured by the manufacturers and has become a way of forcing products onto the market instead of an actual safety standard where NESC is a product of the end users. For example despite zero evidence of any actual reduction in fires, entirely fake products that don’t really do anything but fool the tests, and constant nuisance tripping not only has NFPA not eliminated or stopped promoting AFCIs but they keep increasing the mandates. They have also blatantly added coordination requirements written in a way to promote a small number of fuse manufacturers, and have added so many label requirements that it has become a blatantly violation of the same ANSI standard that they require compliance with, In contrast NESCs biggest fault is that they watered down the arc flash rules so much that OSHA publicly snubbed it in the 2015 regulatory update to 1910.269, but that’s almost the only blatant issue with it. There are some issues still to be ironed out. For instance with wind rules for pole lines it ignites terrain modifiers (terrain type B is assumed) and they simply arbitrarily ignore severe wind for any pole 60 feet or less.

So I can’t say they have anything in common.
 

EmpireWind

Member
Location
Virginia
Occupation
Electrical Engineer
Thank you for your clarification.
So to enlighten my situation, I am working on providing input into design package for wind farm. And then also putting together electrical safety rules for the wind farm.
The voltages are as follows:
Wind Generator : 690V stepped up to 66kV. - so NEC upto Transformer? and Then NESC from the transformer itself?
Substation 1 - 66kV to 240kV (Xfmr + Swgr) and an aux feed 138kV to 480V. So NESC at high voltages? and NEC for aux load feed and equipment?
Substation 2 to POI- 240 to 360 kV (Xfmr + Swgr) or 240kV to 138kV (Xfmr + Swgr) and aux feed 138kV to 480V. So NESC at high voltages and NEC for aux load?
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
The NEC has a serious issue with medium voltage systems as it does not provide adequate coverage. However, if the system is on the load side of the service point, the installation is legally under the jurisdiction of the NEC. Many AHJs recognize the short comings of the NEC for these applications and look to the engineering design and/or the NESC.

There is an attempt to make major changes in the NEC to cover medium voltage systems and there are more and more medium voltage systems on the load side of the service point. If this happens, it will be a multi-cycle process. The proposals for the 2023 code would create a number of new articles that will contain the existing medium voltage rules, with the idea that those articles will be greatly expanded over the next two or 3 code cycles. There has been mixed reaction by the various code making panels at the panel meetings. Some have accepted the proposed medium voltage articles, but most rejected them. This will probably be decided by the correlating committee as they set up the Task Group that submitted the PIs for the new medium voltage articles.
 

kwired

Electron manager
Location
NE Nebraska
NEC and NESC both cover what the industry calls low and medium voltages. NESC pretty much applies to utility side of things and NEC to non utility side of things. Utilities do have low voltage secondaries, non utility applications do have voltages over 1000 volts.

I don't know if NESC has same definition of "service point" as NEC, but that is the magic line where NEC stops applying from the NEC side of things.

If what you have is owned and maintained by a utility company chances are NESC applies. If not owned and maintained by a utility company then NEC likely is what applies. Some localities may change the rules some but that is the way things work as worded per NEC. If NEC is adopted by law as what applies then that is the rule if no amendments that say otherwise.
 

EmpireWind

Member
Location
Virginia
Occupation
Electrical Engineer
Based on the responses above, I am deducing that there is no clear definition of what is considered low, medium and high voltage.
And that it is upto the company that is developing and operating a generating resource to determine what standard to follow?
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Based on the responses above, I am deducing that there is no clear definition of what is considered low, medium and high voltage.
And that it is upto the company that is developing and operating a generating resource to determine what standard to follow?
It is up to the AHJ if the installation is on the load side of the service point.
 
(All that above)
A good way start thinking about it is that the NEC is primarily a fire prevention code whereas the NESC is a safety code. Also that they speak to differing levels of professional engineering supervision and training. There are places where both would logically apply. And if your wind farm qualifies as a utility....
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
(All that above)
A good way start thinking about it is that the NEC is primarily a fire prevention code whereas the NESC is a safety code. Also that they speak to differing levels of professional engineering supervision and training. There are places where both would logically apply. And if your wind farm qualifies as a utility....
That is the big issue ... many of these facilities are not operated by regulated public utilities and where they are not operated by a regulated public utility, the installation falls under the jurisdiction of the NEC, even though the NEC was never written for that type of installation.
 

EmpireWind

Member
Location
Virginia
Occupation
Electrical Engineer
That is the big issue ... many of these facilities are not operated by regulated public utilities and where they are not operated by a regulated public utility, the installation falls under the jurisdiction of the NEC, even though the NEC was never written for that type of installation.
Since the facility will have voltages from 13.8kV to 345kV, I would not think that NEC applies except for voltages below 1000V in which NEC?
So should the standard to refer to be NESC?
 

myspark

Senior Member
Location
SCV Ca, USA
Occupation
Retired EE
That is the big issue ... many of these facilities are not operated by regulated public utilities and where they are not operated by a regulated public utility, the installation falls under the jurisdiction of the NEC, even though the NEC was never written for that type of installation.

Who said so?

This is like proclaiming that Martha Stewart is the sole authority on deciding how much salt and spices are needed for a sumptous dish that everyone will enjoy.

California is the largest producer of wind energy and the EPA is the one responsible for approval of every wind farm and the involvement of NSF and NASA for the technical aspect.

Tell us who the expert at NEC-- who knows every aspect of wind energy manufacture and installation.

Tempest in a teapot.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
Licensed Electrician
Who said so?

This is like proclaiming that Martha Stewart is the sole authority on deciding how much salt and spices are needed for a sumptous dish that everyone will enjoy.

California is the largest producer of wind energy and the EPA is the one responsible for approval of every wind farm and the involvement of NSF and NASA for the technical aspect.

Tell us who the expert at NEC-- who knows every aspect of wind energy manufacture and installation.

Tempest in a teapot.
So you think the EPA is engineering the electrical infrastructure for wind farms in California?
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
Licensed Electrician
Yes, what could possibly go wrong? :rolleyes: Google "King Gold Mine spill 2015"
I don't have to google it I was there, not right on site but Silverton is 25mi as the crow flies from my driveway. I was working halfway between Durango and Siverton that day and got to watch the big blob of orange goo come down the river. That whole fiasco was decades in the making and was the fault of the EPA.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Who said so?

This is like proclaiming that Martha Stewart is the sole authority on deciding how much salt and spices are needed for a sumptous dish that everyone will enjoy.

California is the largest producer of wind energy and the EPA is the one responsible for approval of every wind farm and the involvement of NSF and NASA for the technical aspect.

Tell us who the expert at NEC-- who knows every aspect of wind energy manufacture and installation.

Tempest in a teapot.
Both the NEC and the NESC set the point of demarcation between the applicable codes as the service point. On the line side of the service point it is the NESC and on the load side of the service point, it is the NEC.
 

paulengr

Senior Member
Thank you for your clarification.
So to enlighten my situation, I am working on providing input into design package for wind farm. And then also putting together electrical safety rules for the wind farm.
The voltages are as follows:
Wind Generator : 690V stepped up to 66kV. - so NEC upto Transformer? and Then NESC from the transformer itself?
Substation 1 - 66kV to 240kV (Xfmr + Swgr) and an aux feed 138kV to 480V. So NESC at high voltages? and NEC for aux load feed and equipment?
Substation 2 to POI- 240 to 360 kV (Xfmr + Swgr) or 240kV to 138kV (Xfmr + Swgr) and aux feed 138kV to 480V. So NESC at high voltages and NEC for aux load?

Not at all. Voltage has nothing to do with it.

Let’s step back to regulations. OSHA has 30 CFR 1926, 30 CFR 1910.269, and 30 CFR 1910.300-399.

1926 is for construction and major maintenance.

1910.269 covers generation, transmission, and distribution. This is you. I don’t know where the original came from. It doesn’t look like any standard.

1910.3xx covers utilization equipment. Half is a very old simplified NEC. The other half is taken from a 1980s edition of 70E. It is very out of date but it took OSHA 16 years to update 1910.269 so they’re not interested in writing more regulations.

So the vast majority of your equipment falls under 1910.269. However for instance lights inside the nacelle are utilization circuits and fall into .300-399. Read 1910.269 annex A. It is very clear how this works as well as commingled.

Now let’s bring up two major differences. Under 1910.269 everyone must be qualified. There is no general public. So it is assumed you know what you are doing or know when you are in over your head and avoid it. Second de-energizing is mandatory except under special circumstances under 1910.300-399. It’s encouraged under 1910.269 but most of the equipment and tools is designed for hot line work. Neither of these sound like a big deal but they are pervasive in the regulations and standards. Simply put they aren’t compatible. I am a contractor. I work in mines, government facilities, Duke, and Dominion among others. I’ve participated in drafting IS/Canadian/Trinidad corporate standards across different types of plants. So I’m familiar with all of them and the gotchas.

NESC is a consensus safety standard, not legally binding. So they have a scope but they are at odds with OSHA and NEC. Similarly read the scope in NEC and it’s obvious they are not legally binding either and thus will be state law. And they try to stick their heads in the sand when it comes to utilities. I’ll throw this out there too. The RUS standards are written for utilities (co ops) just starting out. It’s a lot more down to Earth. You may want to start there.

So you need to follow 1910.269 Annex A for “scope”. If it’s utilization use NEC as an equipment standard. If it’s anything else use NESC. For work methods follow NESC generally but make sure you are using it to fill in details 1910.269 doesn’t cover.

Get the voltage thing out of your head because that’s not how it works. Utilities try to just ignore NEC but they can’t quite get there and Annex A is where OSHA clarified this.

You could consider 70E for work rules but that is not written with utilities in mind. Don’t go there.

Stop with the voltage thing. If it’s utilization like lights and receptacles then NEC applies. Otherwise it’s all NESC. Very simple to understand. Just ask what it does and you have your answer.
 
Since the facility will have voltages from 13.8kV to 345kV, I would not think that NEC applies except for voltages below 1000V in which NEC?
So should the standard to refer to be NESC?

Well...... IMHO and all that......
The NESC is a good safety code for distribution and transmission, any utilities on-site will use that.
It's probably a good safety code for everything involved.
Any utilization equipment and wiring will need the NEC.
A lot will depend on the AHJ and their interpretations of where the two codes cross.
 

paulengr

Senior Member
Based on the responses above, I am deducing that there is no clear definition of what is considered low, medium and high voltage.
And that it is upto the company that is developing and operating a generating resource to determine what standard to follow?

Low voltage is internationally recognized as 1000 V or less. Medium goes from there to 35 kV. High is from there to around 300 kV.

However the NEC somehow came up with 600 or less is low and above that is high. It got codified into OSHA. Due to the prevalence of power electronics and use in PV solar there is a recognized need for NEC to adopt international standards. They are reluctant to do so because of OSHA and OSHA isn’t too interested in changing the regulation due to the time and effort involved. They would rather drop the regulation and just reference standards as they have done with 70E but politically this isn’t possible.
 

paulengr

Senior Member
That is the big issue ... many of these facilities are not operated by regulated public utilities and where they are not operated by a regulated public utility, the installation falls under the jurisdiction of the NEC, even though the NEC was never written for that type of installation.

OSHA is clear on this. If it quacks like a duck...the example they use us a sugar plant that also has a large cogen. They are required to follow 1910.269 even if they are not per se a “utility”.

A number of plants have extensive waste heat or waste fuel recovery systems. For instance many land fills run large CAT diesel generators modified to run on methane (landfill gas) rather than flaring it off. These facilities run very much like a utility and they are clearly 1910.269 even though many never produce much more than enough power to offset the light bill.

NEC clearly scopes out such facilities. Plus it doesn’t have to be the whole facility, using 1910.269 Annex A as a template. The “.269” area may extend to the point where the breakers tie into a facility’s substation. Up to that point it is clearly “generation”. After that point if the facility is a net power consumer it’s an easy argument to make that it’s an NEC facility from there on, although the substation switchgear is “commingled”.

Utilities would like to label everything NESC. Industrials want to call everything NEC / 70E. It’s not that black and white. And the scopes of NEC and NFPA are not coordinated at all. If the correlation committee wants to be useful, focus on that!
 

paulengr

Senior Member
Both the NEC and the NESC set the point of demarcation between the applicable codes as the service point. On the line side of the service point it is the NESC and on the load side of the service point, it is the NEC.

I suggest you actually read the scopes because they don’t describe it that way or state this in any way. NEC comes closest to this idealistic view but still fails. And they don’t correlate to each other. And both are in conflict with OSHA. So try again. Better copy/paste from the scopes, all 3 of them.

Part of this comes from the fact that the NFPA and IEEE groups hate each other, as in Hatfields and McCoys feuding hate, and OSHA doesn’t trust either of them. So you can’t even attempt to suggest agreement without getting shot at.
 
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