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 It is very out of date but it took OSHA 16 years to update 1910.269 so they’re not interested in writing more regulations.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.