[RE-wrenches] Cable tray

[John Berdner]

Dan:

I have to disagree with your statement regarding costs and voltage.
While clearance and creepage distances increase at 1000V this makes only some things larger.
Example: The control electronics and all ac output circuitry remain the same.
Although the spacing between the high voltage dc components increases, the power of the device also increases and the losses decrease.
The result is that the product >>might be a little larger<< but its power rating will be higher and it will likely be more efficient.
For a given current level the higher voltage might increase the unit price slightly but the $/Watt will almost certainly decrease.
Conversely if power is held constant the current will be lower and so the product may in fact be cheaper that a 600V product of the same power rating.

Once we get past the unit price for components there is no doubt that system costs for 1000V are significantly lower than for 600V.

Let's review...

Ohms law:
P=V*I, so for a given power level voltage and current are inversely linked linearly - if the voltage increases the current decreases.
P=I^2 * R, so for a given power level, increasing the voltage decreases the current and decreases the losses by square of the change.
1000/600 = 1.667 => P_loss= 1.6667^2, so for a given power level and given piece of wire, the losses are 2.777 times lower at 1000V than at 600V.

Wire and Ampacity:
The ampacity of a wire is based on current not voltage
Higher voltages mean 1.667 times more power on a given piece of wire in a given conduit (yes the conduit might need to be bigger due to fill factor - it depends).
Another way of saying this is 1000 Vdc gives you a 40% reduction in wiring costs for a given power level compared to 600Vdc.
Small gauge PV wire is already available from multiple sources with 1000 and 2000 V  ratings for a small premium over 600 V wire.
Why ? - Current = conductive materials = expensive.  Voltage = insulating materials = inexpensive.
Larger gauge PV wire and USE-2 is still a bit hard to find but are both available in commonly used PV sizes from multiple sources

Fuses and Combiners:
kW per string is a key cost metric for installed BOS costs and more is better.
Fundamentally, series trumps parallel every time.
Higher voltages = longer strings = more power per string = less strings, fuses and holders (combiner inputs).
1000 V string fuses / holders are available from multiple sources and are competitive with 600V counterparts.

Switches:
1000V switchgear cost is still lagging in the US but we are starting to see more reasonably priced equipment on the horizon.

Summary:
1000V PV is well proven outside the US.
In the US the tide is turning and we are rapidly headed to 1000V commercial systems.
The Codes and Standards are already in place and we are beginning to see reasonably priced 1000 Vdc rated components.
1000Vdc Listed Modules, 1000/2000Vdc UL 4703 PV wire, Listed 1000Vdc string fuses and holders, Listed 1000Vdc inverters are all available today.

I believe 600Vdc commercial and utility scale systems will rapidly become uncompetitive and, within a few years, the exception rather than the rule.

Best Regards,

John Berdner
General Manager, North America

SolarEdge Technologies, Inc.
3347 Gateway Boulevard, Fremont CA 94538 USA  (*Please note of our new address.)
T: 510.498.3200, X 747
M: 530.277.4894

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Exeltech
Sent: Sunday, March 31, 2013 9:10 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Cable tray

Hello Chris,

>From a manufacturer's perspective .. you're incorrect on all assumptions.
(Sorry.)

It costs more to make higher-voltage anythings.

Higher voltage means: Clearance / creepage distances are larger (thus bigger
parts or products).  Insulation must be thicker (or have a higher dielectric rating).
This results in more rigorous (consequently more expensive) UL testing.  Etc.
All adds up.

Dan


--- On Sun, 3/31/13, Chris Mason <cometenergysystems at gmail.com<mailto:cometenergysystems at gmail.com>> wrote:

From: Chris Mason <cometenergysystems at gmail.com<mailto:cometenergysystems at gmail.com>>
Subject: Re: [RE-wrenches] Cable tray
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>>
Date: Sunday, March 31, 2013, 8:21 AM
As we see more 1000V installations, chances are that 600V rated equipment will find its way into installations it is not rated for. To avoid problems and so we don't need two SKUs and lots more inventory, the manufacturers need to move all their product to 1000V ratings. I suspect it does not cost more to make 1000V wire than 600V, similarly disconnects, fuses, fuse holders and connectors.


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