[aprssig] Fwd: The end of daytime HF?

Robert Bruninga bruninga at usna.edu
Fri May 4 13:52:53 EDT 2018

But unlike existing PLC comms which are all from the array modules to the
central house system and only informatinve info, this shut-down signal will
presumably be the other way, and so if a loss of this signal occurs, the
affected panels shut down.  I can envision that a poorly designed system NOT
taking into account the possibility of high power Amateur RF in the
vicinity, might fail to detect this signal an could shut down in the
presence of hig RF.

Just something to look out for as these systems proliferate.

Bob, WB4aPR

-----Original Message-----
From: aprssig <aprssig-bounces at tapr.org> On Behalf Of KF4LVZ
Sent: Friday, May 04, 2018 12:53 PM
To: aprssig at tapr.org
Subject: Re: [aprssig] Fwd: The end of daytime HF?

If you look at the proposal it does say that it only requires rapid
shutdown, but it does NOT say that it absolutely requires PLC type
communication. The reason is that the code is not precluding standard
whole-array inverters (rather than micro inverter).  It just wants a module
of some type (such as a relay) that can disconnect all the modules and
ensure the DC voltage is below 80V at the terminals.

A couple vendors want to unify the PLC protocols already in use on
microinverters for power management and tracking to include the necessary
commands for array disconnects.

The PLC currently in use on solar arrays is on the order of 100-200 kHz
carriers.  So you should already be seeing a problem if there was one
because it's already fairly widespread with the extensive use of
microinverters for things like Maximum Power Point tracking and array health

You also have much smaller radiating wires.  Because this system requires
two components (a receiver at the array and a transmitter at the point of
connection to the mains) the transmitter also is required to contain
filtering to prevent signal from going past the transmitter and into the
mains system (where it could interfere with other array systems in
neighboring areas). Thus, unlike BPL, the radiators are the short lengths
from the arrays down to the controller/transmitter.  This is again assuming
a microinverter ssytem using PLC.  A system that uses a separate signalling
wire will have no such limitation and the NEC does not preclude this option.

On 2018-05-03 19:21, Robert Bruninga wrote:
> I don't want to be an alarmist, but we need the Hams with the proper
> knowledge to get involved in this disturbing news.
> The National Electric Code now requires electronics on every module of
> a solar array communicating  via signalling on the DC power lines to
> assure EACH pair of panels can shut down independently.  This is to
> make all possible faults never allow more than 80 volts anywhere in the
> system.
> This is effective 1 Jan 2019
> This is the nail in the coffin of simple DC series string arrays which
> are the quietest systems and almost demands microinverters or
> optimizers on every panel.  Refer to the QST article a few years ago
> about how disastrous optimizers are to RFI and HF operations with modules
> all over the roof..
> Here is the Solar news:
> https://solarbuildermag.com/bos/nec-2017-module-level-solar-system-shu
> tdown/
> Also, what is going to happen to an array that has signaling all over
> it in the near field of HF?
> Although you can avoid it by going solar before then, you may have
> problems when your neighbors go later.
> I hate  to be an alarmist but we all know what happens when ham radio
> and commercial systems are incompatible and even though Ham radio
> might be in the right, we are only 1 in 600 and no one is going to side
> with us.
> We took on broadband over power and squelched that dumb idea, but now
> this has the potential for equal demise of Ham radio.  It should be
> fixable, but we also know that there is high competition in the solar
> market and the modules that are made the cheapest  will be popular and
> will likely not be adequately filtered.
> Sorry for posting to the APRS group but it is the only HAM email
> reflector I subscribe to besides AMSAT..
> If nothing else, we need to find out what systems are terrible
> emitters and nip them in the bud.  Maybe all it takes is driving by
> solar systems you see and turing on your AM radio on a weak signal
> channel and seeing if the background noise peaks near that home.  But
> also it has individual peaks, so it might also be nice to tune around
> too find the max and then check the range.  I find the noise can go
> hundreds of feet along the power lines....
> You cant miss  em... just sounds like a 60 Hz buzz on all the
> harmonics of the inverter switching frequency.
> Bob
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