Solar Panel and Wind Turbine Power in the Same Cable

SolarWindBoy

Hi,

At home, I have both a 15kW AC wind turbine and a 1000V solar array in my garden. To decrease the cable losses between the generators and the inverters I am looking at installing a higher gauge wire.

I had spotted that it was cheaper to buy a 5-core cable as opposed to a 2-core and 3-core cable. So I wanted to check if it was safe/legal to use a 5-core cable.

In NEC 690.31B I saw it says that they should be separated by a partition. Would the insulation around the conductors be suitable for this?

Or should it be 2 separate cables installed in 2 separate conduits?

Thank you for any help that can be offered with this.

BB.

One discussion on updated 2023 Code:

https://www.electricallicenserenewal.com/Electrical-Continuing-Education-Courses/NEC-Content.php?sectionID=1554.1

2020 Code Language:

690.31(B) Identification and Grouping. PV system dc circuits and Class 1 remote control, signaling, and power-limited circuits of a PV system shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. PV system dc circuits shall not occupy the same equipment wiring enclosure, cable, or raceway as other non-PV systems, or inverter output circuits, unless the PV system dc circuits are separated from other circuits by a barrier or partition. PV system circuit conductors shall be identified and grouped as required by 690.31(B)⁠(1) and (B)(2).

Exception: PV system dc circuits utilizing multiconductor jacketed cable or metal-clad cable assemblies or listed wiring harnesses identified for the application shall be permitted to occupy the same wiring method as inverter output circuits and other non-PV systems. All conductors, harnesses, or assemblies shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.

2023 Code Language:

690.31(B) Identification and Grouping.

N (1) Conductors of Different Systems. Where not otherwise allowed in an equipment’s listing, PV system dc circuits shall not occupy the same equipment wiring enclosure, cable, or raceway as other non-PV systems or inverter output circuits unless separated from other circuits by a barrier or partition.

Exception: Where all conductors or cables have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the same wiring method, the following shall be permitted:

(1) Multiconductor jacketed cables for remote control, signaling, or power-limited circuits shall be permitted within the same wiring enclosure, cable, or raceway as PV system dc circuits where all circuits serve the PV system.

(2) Inverter output circuits shall be permitted to occupy the same junction box, pull box, or wireway with PV system dc circuits that are identified and grouped as required by 690.31(B)(2) and (B)(3).

(3) PV system dc circuits utilizing multiconductor jacketed cable or metal-clad cable assemblies or listed wiring harnesses identified for the application shall be permitted to occupy the same wiring method as inverter output circuits and other non-PV systems.

If this installation needs to be inspected (AHJ--Authority Having Jurisdiction), then talk with your inspector about what they "want".. The PV DC exception is written such that PV circuits are "similar" to AC inverter output and would be "similar" to the AC branch circuits in building wiring.

The original intent (from decades ago when I worked on the MFG equipment side) was that we "should not" mix AC branch circuits (relatively high voltage/power) with signaling circuits (data, 24 volt, no/low voltage/low power) wiring for safety--Any failure would not allow energy from "dangerous" circuits to connect to what should be "safe" energy circuits.

And related, was that all wiring in a "conduit" or bundle had to be rated for the same max voltage--Could not mix 600 VAC and 24 Volt rated insulation wiring--All had to be rated to 600 VAC.

I would argue that an inspector should accept your "single" cable wiring shared between PV, Wind, and even AC branch circuit wiring. This could be argued that Wind AC is not listed as an exception--And should not be allowed--But PV wiring was excepted to be mixed with DC and AC wiring.

Obviously, the physics of electricity and insulation did not change between 2020 and 2023--Just a code jockey's feelings about mixing.

Looking at your usage... What is your acceptance of initial lightning induced failure and subsequent failures... I.e., what is the wind turbine was hit by lightning--Sharing a raceway/cable bundle would likely bring that lightning energy (virtually unlimited voltage and current wrt your equipment) into your solar wiring. And a good chance of damaging the solar side of your system too.

Would running separated Wind and PV wiring be "worth it to you" to limit costs/exposure between wind and solar systems to run separate conduit/raceways for the two systems (and keep your AC branch circuits isolated too)?

I believe you are in the UK... Is this for a USA/North America installation?

Will you be using surge suppressors on your Wind and PV installation?

https://www.solar-electric.com/catalogsearch/result/?q=surge+protection

-Bill

SolarWindBoy

Thank you for the reply! I am in the UK, but this installation is actually in the Maldives (They don't really seem to have in-depth standards so that's why I have been following NEC).

I have surge suppressors for the PV, but for the wind, I am struggling to find any as the generator's nominal voltage is 520V and all the AC SPDs I can find are rated for lower mains voltages. 

BB.

I don't have any specific suggestions for higher voltage surge suppressors... Here is a nice white paper on them:

https://www.eaton.com/content/dam/eaton/services/eess/eess-documents/sa01005003e.pdf

And, for example, in the USA, 480 VAC power is common for industrial use--And you can find supressors for that voltage (this example is not cheap):

https://www.se.com/us/en/product/SSP05XDSE20A/surge-protection-device-xdse-200ka-480-vac-delta-3-phase-3-wire-spd-type-2/

When you get into wind turbines/alternators... You get into details which you may not comfortable in dealing with... For example, in Three Phase equipment, there are "Delta" and Wye (or Star) connected windings. If you have Wye wound alternator for the trurbine, you could are looking at 480 VAC between L1/L2/L3, but only 277 VAC between L1 and Neutral (the "center tap" of Wye or Star configured windings). Which could (possibly) let you use Lower Voltage rated surge suppressors (Lx to Neutral vs L1/L2/L3 connected surge devices).

https://www.allaboutcircuits.com/textbook/alternating-current/chpt-10/three-phase-y-delta-configurations/

Given that this would appear to be a difficult salt water (shoreline) environment--Keeping out the salt air/controlling corrosion, I would guess, is a major issue too.

Anyways--Some thoughts. Good Luck!

-Bill