truly dictatorial [RE-wrenches]

[Rob Wills]

Hi Larry - your comments are quite right - islanding has a very low
probability of occurring, and utility safety practices make the chance of
actually harming a lines person very close to zero.

On the other hand, if a technology is not widely introduced, and it has the
very slightest potential danger, to personnel or power quality, then it is
easier for utilities to "just say no".

That is why "non-islanding inverters" were and are essential to the process
of making PV "plug and play".  It took the argument off the table.

It's possible to make non-islanding inverters with low current THD, and with
modern designs, it really does not add to the cost - it's a few more lines
of software.

Regards

Rob Wills
Advanced Energy



-----Original Message-----
From: Lawrence Elliott [mailto:larry at energyoutfitters.com]
Sent: Thursday, December 13, 2001 5:21 PM
To: RE-wrenches at topica.com
Subject: Re: truly dictatorial [RE-wrenches]




Rob Wills wrote


The comment "truly dictatorial institution" is quite unfair and should
not
> go unchallenged.
>
> The standard that UL uses to test inverters, UL1741, is an industry
> consensus document.  It was written in years past with input from
Trace (and
> myself, and Bill Brooks, and many utility engineers).  It is
harmonized with
> the NEC and IEEE 929.
>
> The standards development effort was and is supported by the US DOE
and the
> SEIA.  It is open to all.  If you have suggestions for any of these
> standards, please email me, or Tim Zgonena at UL, or Ward Bower at
Sandia,
> and we will work to bring them in to the next round.  (There was a
UL1741
> advisory group meeting about 3 weeks ago that was well attended)
>


Rob. My words were fairly strong but I'm not convinced they were unfair.
Sorry!

I suppose my choice of words comes from having seen this same thing all
too often in the aircraft industry I used to work in.

It never ceased to amase and sometimes amuse me how two sets of
engineers could be working on the same issues except one actually worked
closely with the technology and the other simply regulated it.
I am not for one minute challlenging the ability of any of the
UL//Sandia/etc engineers.
I simply get very frustrated when regulations are imposed for a problem
that statistically and even in actuality don't add up.

Islanding. Okay so we have 20-30 kw of Pv installed in one service
district. An inverter fails to shut down. First what are the statistical
odds. Million to one maybe. Have any real world data. Bet very little if
any. Lets ask what if any problem this poses.

Grid goes down. Inverters run. Line stays hot but guaranteed to be very
unstable in all parameters. Very likely inverters die in seconds or a
few minutes at worst.
Perhaps a few appliances or something gets "brown out" or fail at worst.

Utility checks line. Line still active. Hot stick line to ground and the
anemic 30 kw dies.
Maintain ground till line repaired.
Odds of inverter reinitializing before power up. Million to one?
Personell and area cleared and checked before ground unlatched and re
power up.
Power up with inverters down or up. So what. Inverter fails perhaps.
Grid didn't even know it was there.  Reinitialize and go about our
business.

Problem solved.
Many engineers I have worked with have the same problem.
They follow Parkinsons Principle of Pyramiding Pride or in other words
never heard of the K I S S principle.
Just pure frustration talking here.

Like I said if anyone sees a reason to challenge my logic feel free. I'm
all ears and I'm sure other wrenches are and if I am wrong I will admit
to it. And I will have learned something.
Political power plays be damned.

Larry Elliott
>
> ==^================================================================
>
>
>
>

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