Hi Guys

please can i have your opinion in running DC volts through armored cable. Copper and aluminum. To be used to connect solar panels to inverter. 150m distance. 800v

 

Some say that in armored cable induction will cause the insulation to deteriorate and short and burn after a while.
 

Also more voltage drop  in armored cable. 
 

thanks

57 minutes ago, Voltageza said:

Hi Guys

please can i have your opinion in running DC volts through armored cable. Copper and aluminum. To be used to connect solar panels to inverter. 150m distance. 800v

 

Some say that in armored cable induction will cause the insulation to deteriorate and short and burn after a while.
 

Also more voltage drop  in armored cable. 
 

thanks

No problem as long as the cable has the correct voltage and current rating. Most large PV system use armoured cable. 1500V I guess is fine. 

Most statements to me is fake. If I am wrong plase correct my answer. 

The cable offers good protection for direct burial in the ground. If induction is a problem then use 2 core cable. It's also available. The voltage drop I think will be minimal because the DC voltage is high. @TaliaBwhat's your take on this? Most PV installations according to SANS requires metal trunking & bonding of that trunking for obvious reasons. The Voltage & amperage of the armoured cable is not exceeded but this cable is mainly used for AC applications...

A very interesting case this as well as a deep dive into what is allowed & not allowed.

53 minutes ago, Steve87 said:

The cable offers good protection for direct burial in the ground. If induction is a problem then use 2 core cable. It's also available. The voltage drop I think will be minimal because the DC voltage is high. @TaliaBwhat's your take on this? Most PV installations according to SANS requires metal trunking & bonding of that trunking for obvious reasons. The Voltage & amperage of the armoured cable is not exceeded but this cable is mainly used for AC applications...

A very interesting case this as well as a deep dive into what is allowed & not allowed.

Out of memory over the years I have never seen specs mentioning AC or DC. I would guess our normal armoured cable 600/1000V refers to 600AC and 1000DC. Although I mention never welding cable is normally indicated to the same voltage for AC or DC.

We get to know these cables used for AC but where viable speed drives (DC) are used in the industry the same cable is used to equipment like motors and control gear. We also know trunking but in industry cable trays are normally used or even concrete trenches like in ALL Eskom substations.

Here is one of the very few specs where AC and DC is mentioned.

Edited July 28, 20241 yr by Scorp007

Armoured cable or SWA cable may be used in dc applications. Armoured cables offers superior protection properties against damage in all types of applications. Sans does not specify beyond current and voltage ratings that armoured cable should not be used on dc curcuits.

4 hours ago, Voltageza said:

150m distance. 800v

You should calculate the voltdrop at 150m distance you spesified as to not exceed 5% between input voltage and output voltage in your case not exceeding 760v at the Mppt input side.

Also no need for earthing the armouring of the cable in dc applications as it will serve no purpose like in AC applications.

You will most likely ( not sure of your array current) use 2.5mm 2 core ( rated current 36A) that has a voltdrop of 19mv/A/m so in your case 0.019 x (X unknown) x 150m. (Copper)

Edited July 28, 20241 yr by TaliaB

2 hours ago, TaliaB said:

Armoured cable or SWA cable may be used in dc applications. Armoured cables offers superior protection properties against damage in all types of applications. Sans does not specify beyond current and voltage ratings that armoured cable should not be used on dc curcuits.

You should calculate the voltdrop at 150m distance you spesified as to not exceed 5% between input voltage and output voltage in your case not exceeding 760v at the Mppt input side.

Also no need for earthing the armouring of the cable in dc applications as it will serve no purpose like in AC applications.

You will most likely ( not sure of your array current) use 2.5mm 2 core ( rated current 36A) that has a voltdrop of 19mv/A/m so in your case 0.019 x (X unknown) x 150m. (Copper)

Hi TaliaB

Thank you for the info.

Array is 10 rows of 60 panels. 4 x 15panel strings in each row. 2 rows per Atess 8string Combiner box. Going to 3 x Atess HPS150s. Using the Trina Tallmax 550W

Will be 750v and 14.02 per string.

 

11 hours ago, Voltageza said:

Some say that in armored cable induction will cause the insulation to deteriorate and short and burn after a while

Just to put your mind at ease on above assumption that induction could damage the inner core insulation. Below manufacturer specify AC or DC on the 2 core armoured cable. Alvern and Aberdare cable manufacturers do also spec for Ac and Dc on 2 core cables.

Edited July 28, 20241 yr by TaliaB

15 hours ago, TaliaB said:

Just to put your mind at ease on above assumption that induction could damage the inner core insulation. Below manufacturer specify AC or DC on the 2 core armoured cable. Alvern and Aberdare cable manufacturers do also spec for Ac and Dc on 2 core cables.

I notice the picture refers to 90°C while some manufacturers will show lower current ratings as they use 70°C.

9 hours ago, Scorp007 said:

I notice the picture refers to 90°C while some manufacturers will show lower current ratings as they use 70°C.

Maybe the temperature reference depends whether it's a cross-linked polymer (XLPE) or standard PVC insulated SWA cable

On 2024/07/28 at 10:31 AM, Scorp007 said:

Out of memory over the years I have never seen specs mentioning AC or DC. I would guess our normal armoured cable 600/1000V refers to 600AC and 1000DC. Although I mention never welding cable is normally indicated to the same voltage for AC or DC.

We get to know these cables used for AC but where viable speed drives (DC) are used in the industry the same cable is used to equipment like motors and control gear. We also know trunking but in industry cable trays are normally used or even concrete trenches like in ALL Eskom substations.

Here is one of the very few specs where AC and DC is mentioned.

The insulation voltage rating should be higher for DC than AC because AC voltages are stated as RMS values so if it's a 230v supply ie it tests at 230v with your multimeter then the actual peak voltage the insulation is seeing is √2×230=325V. So in theory a cable that's rated to 600VAC should be rated to at least 849VDC. There are however other factors that can skew the ratings figures.

Edited July 29, 20241 yr by Marv

2 hours ago, Marv said:

The insulation voltage rating should be higher for DC than AC because AC voltages are stated as RMS values so if it's a 230v supply ie it tests at 230v with your multimeter then the actual peak voltage the insulation is seeing is √2×230=325V. So in theory a cable that's rated to 600VAC should be rated to at least 849VDC. There are however other factors that can skew the ratings figures.

Good point. Back to the 90 degrees. Surely if it was XLPE would the insulation type still be called thermo plastic as per the picture earlier? 

Apologies, I didn't see the thermoplastic classification. It won't be XLPE in that case, maybe polyurethene or some kinda PVC. I wish they'd just state the actual plastic they use rather than the family of plastics, it would be a lot more useful. Problem nowadays there's so many variations of each plastic even that wouldn't really help because they're all chemically cocktailed to their specific application meaning there's dozens of variations of PVC so you'd have to use the IEC 60811 classification which wouild be complicated but handy if you're considering a cable for an application that's unusual.

I think manufacturers just need to produce better data sheets that are more relevant to ever evolving modern day uses. Twenty years ago a simple temp and CCC rating with different installation methods was fine but nowadays it's way short of the mark. They should state figures that indicate their suitabiliy for AC (normal 230/400v supply), DC such as solar PV etc, high frequency AC and modulated DC for VFD applications etc. Unfortunately that's not going to happen unless there's legislation or a requirement in the 10142 regs for it to be supplied on products sold. 

 

On 2024/07/28 at 7:48 AM, Voltageza said:

Some say that in armored cable induction will cause the insulation to deteriorate and short and burn after a while.

That is nonsense. Induction is a phenomena of alternating currents. You are dealing with DC from the panels. What you have to pay attention to is the useful section to carry the current, as well of the center conductor as of the shield, that is if you use the shield for the return. All other challenges have already been mentioned.

8 hours ago, Beat said:

That is nonsense. Induction is a phenomena of alternating currents. You are dealing with DC from the panels. What you have to pay attention to is the useful section to carry the current, as well of the center conductor as of the shield, that is if you use the shield for the return. All other challenges have already been mentioned.

How dare you say this. May be it came via the barber who heard it from his/her brother in law who heard it from his mother in law after a good braai. Hehehe

Edited August 9, 20241 yr by Scorp007

I work in substations, where all panels are wired with either 220V, 110V or 48V DC and some with quite high loads with thousands of amps. We use regular armoured cable with no issue. Just make sure you don't exceed the manufacturer voltage/current rating of the cable. I've seen some substations running for 50 years with no issues, unless there's a pre-existing cable defect or someone chops into it. AC should not be run in the same cable as it can superimpose a waveform onto the DC. We normally ground the armour on one side only, but that's due to potential rise in the ground in substations due to HV ground faults.