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Does Twisting The Wires In A Longer PV Run Help Avoid Problems..?

J

JRH

Solar Wizard
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Ya see this discussed now and then , but not very deeply.
Ya see solar articles recommending it here and there but again not with definitive facts….

The overtones of all of these articles are that twisting Or braiding PV wire runs helps lower the chance of EMF or surges jumping on the wires…and causing a problem …..

well it sorta makes sence ….kinda….maybe…..!

I do remember back in my Band Days quality low impedance mic cables used twisted pairs plus a ground shield .It certainly stopped the reception of stray TV/ radio or truckers on CB radio signals … cheap mics and guitars cords didn’t use balenced pairs and picked up hums and other sources of interference.. it may be different today , dunno..

I did weave all three wires of my PV cables (P- N- G) sorta loosely last spring hooking up my 65 ft run back to the SCC and grounding point …and I’m fixing to add more panels in different areas with longer runs ..
is this a waste of cable and time..? Or is there merit to this effort…

I have no real facts to support my effort but did it anyway…
Any opinions….?

Thx….J.J.
 
Audio signals going to an amplifier is a lot different than high voltage DC providing power. In my mind, they are totally different.
 
Like you, I don't have any evidence twisting PV cables does any good .... but, from my experience installing and maintaining building control equipment that often had long power and communication cables .... When in doubt .... Twist them.
We used twisted cabling for everything .... even resistive sensors. Old installations where we hadn't been so vigilant were plagued by mystery problems that disappeared when using twisted wire.

It could, however, be a real pain to twist very long PV cables.
 
Bob B said:
Like you, I don't have any evidence twisting PV cables does any good .... but, from my experience installing and maintaining building control equipment that often had long power and communication cables .... When in doubt .... Twist them.

It could, however, be a real pain to twist very long PV cables.
Click to expand...
Yea… and cost abit too…… Haa…
 
SparkyJJO said:
Audio signals going to an amplifier is a lot different than high voltage DC providing power. In my mind, they are totally different.
Click to expand...
My PV wires are about 86 VOC … I have no idea what the voltage of a the different audio signals would be.
Thanks for the input..J.
 
The PV array is part of the loop area which would pick up EMP etc. and create differential mode voltage.
So you have to "twist" your panel layout as well.

To avoid common mode pickup, I would keep surge arrestors at inverter end only. Then the array becomes a whip antenna, only good pickup for the frequency corresponding to that quarter wave. Loaded by capacitance at the array.

If you had surge arrestors at array as well, sufficient voltage to make them conduct and it becomes a loop antenna (half wave dimension), but also a coil for magnetic fields.
 
Hedges said:
The PV array is part of the loop area which would pick up EMP etc. and create differential mode voltage.
So you have to "twist" your panel layout as well.

To avoid common mode pickup, I would keep surge arrestors at inverter end only. Then the array becomes a whip antenna, only good pickup for the frequency corresponding to that quarter wave. Loaded by capacitance at the array.

If you had surge arrestors at array as well, sufficient voltage to make them conduct and it becomes a loop antenna (half wave dimension), but also a coil for magnetic fields.
Click to expand...
He he he .. … Hedges …. love ya, but you are a trip….seriously… !

Let me please re- phrase the question .. ?‍??‍??‍??‍??‍?.

all 3 PV wires from each array are run together to the charge controller(s) and ground point in a shallow buried conduit.. I only have two choices …push em in and run em …OR ..twist em and push em in and run em…

Going forward does it matter if I twist em or not…?
it sounds like since I have many little blue lite SPD’s all over the place, I probably shouldnt.

As much of it eludes me , would that be a decent interpretation of your message …?,

As always , I appreciate you taking the time to try and help me.

Jim.
 
I think somebody else said not to put SPD at the array, possible path for lightning earth currents to enter and take a shortcut through PV wires into your electronics.

I'm suggesting no SPD at the array to reduce pickup of high energy EMI.

As for twisting, reduced loop area and balanced left/right small loops would be good. But the PV array is a much bigger loop, so I'm not sure twisting wires matters at all. Unless something routed next to the wires could couple to them.

No harm in twisting them, though.
 
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Hedges said:
I think somebody else said not to put SPD at the array, possible path for lightning earth currents to enter and take a shortcut through PV wires into your electronics.

I'm suggesting no SPD at the array to reduce pickup of high energy EMI.

As for twisting, reduced loop area and balanced left/right small loops would be good. But the PV array is a much bigger loop, so I'm not sure twisting wires matters at all. Unless something routed next to the wires could couple to them.

No harm in twisting them, though.
Click to expand...
Now we’re talking…. Gotcha…thank you…
 
The panels are true DC but there will be some pulsed back emf from the mppt as it charges and dumps it's inductor. The more they spent on capacitors, the less of this there will be to see. If you are concerned about stray mag fields, twisting would help. But it will also take more cable to make your run so its not free (cross sectional area increases proportional to the twists per unit length). Also, rotate your spools as you twist the cables so they "lock" together.

I had some slack on my inverter cables from the DC bus and twisted them. Would need a mag field meter or oscilloscope clamp probe to see if it was doing anything as there was no "problem" to "fix".

For ac loads, you can use your phones magnetometer in a sensor app to find wires in your walls. Just put an electric heater on the circuit and you will see a 60hz mag field.
The phone sensor is probably not a high enough sample rate to pick up something like a mppt controller which I imagine operates in the kHz range.
 
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JRH said:
Now we’re talking…. Gotcha…thank you…
Click to expand...

I gotta put my prose through at least a second-order filter.

Previously at work, boss said that at performance reviews/ranking, other people didn't know who I was.
Now I put my mugshot on front page of PowerPoint slides.

After I gave a Teams talk (might have been on inrush tripping breakers?) I heard other employees had said, "He sounds like a professor!" (Can't dazzle them with brilliance ...)

When we get in the right circle, we can just banter that way, because everyone's on the same (electromagnetic) wavelength.
 
65NW said:
The panels are true DC but there will be some pulsed back emf from the mppt as it charges and dumps it's inductor. The more they spent on capacitors, the less of this there will be to see. If you are concerned about stray mag fields, twisting would help. But it will also take more cable to make your run so its not free (cross sectional area increases proportional to the twists per unit length). Also, rotate your spools as you twist the cables so they "lock" together.

I had some slack on my inverter cables from the DC bus and twisted them. Would need a mag field meter or oscilloscope clamp probe to see if it was doing anything as there was no "problem" to "fix".

For ac loads, you can use your phones magnetometer in a sensor app to find wires in your walls. Just put an electric heater on the circuit and you will see a 60hz mag field.
The phone sensor is probably not a high enough sample rate to pick up something like a mppt controller which I imagine operates in the kHz range.
Click to expand...
My teacher in high school said I was Gona be sorry I didn’t pass algebra…now I see why….!
( just kidding) … thanks for the input…?

J.
 
65NW said:
For ac loads, you can use your phones magnetometer in a sensor app to find wires in your walls. Just put an electric heater on the circuit and you will see a 60hz mag field.
The phone sensor is probably not a high enough sample rate to pick up something like a mppt controller which I imagine operates in the kHz range.
Click to expand...

You mean like the non-contact voltage detector in my Harbor Freight clamp meter?

We have a 3-axis magnetic field sensor at work, so I've been using that to measure leakage of some equipment.
 
I think ncv is the e field component because it can detect under no load conditions.
Not sure.

What's its sample rate? Probably higher than a phone mems. Might be able to catch something near a cable during full sun/full charge rate. Then try twisting and see if it goes down.
 
Hedges said:
I gotta put my prose through at least a second-order filter.

Previously at work, boss said that at performance reviews/ranking, other people didn't know who I was.
Now I put my mugshot on front page of PowerPoint slides.

After I gave a Teams talk (might have been on inrush tripping breakers?) I heard other employees had said, "He sounds like a professor!" (Can't dazzle them with brilliance ...)

When we get in the right circle, we can just banter that way, because everyone's on the same (electromagnetic) wavelength.
Click to expand...

I have been in some groups like that on different topics in life ..we did the same thing… it’s fun sparring with others deep into advanced shop talk…even if it gets to the point it’s only academic…I can assure you anyone not at that level will exit the room and go talk to the secretary….
J.
 
Here's some interesting victron threads on mppts causing emi on radio equipment.

Though in the first one the question of what is the switching frequency of their controllers is never answered.

SmartSolar Charge Controller MPPT 150/35 Switching Frequency(s) for selecting RFI Ferrite Choke(s) - Victron Community

community.victronenergy.com community.victronenergy.com

This one is better overall.

RF noise from 150-60 solar charger - Victron Community

community.victronenergy.com community.victronenergy.com

To summarize them, it depends on the panel wiring and grounding as well as the controller, its switching frequency and noise filtering on the lines.
I didn't see cable twisting mentioned specifically but they said to run them together to make a smaller loop area.
 
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