SOV/MOV protection devices [RE-wrenches]

jberdner at sma-america.com jberdner at sma-america.com
Fri May 18 17:24:53 PDT 2001


Kent:

Are you looking a the DC side or the AC side ?

For the AC side GE has a couple of UL listed options that look pretty good
to me.
The GE Surge Pro clips into the main panel like a 2 pole circuit breaker.
This avoids trying to find a knockout to use in a flush mounted panel.
It has a 5 year $20,000 warranty for protected equipment.

They also have a bigger unit that fits in a 1/2" KO.
Sorry I don't remember the part number.
It is higher power and has a 5 year $50,000 warranty on connected equipment.
UL Listed and one time insurance premium on your system - Sold!

On the DC side it is a bit more complicated.
I think the Delta is a recommended component not a Listed device and that
could create some inspector issues.
For a RC technically you need to provide overcurrent protection.
While at APT / Pulse I always thought the anecdotal evidence indicated the
Delta's worked pretty well.
One of the things that is interesting is that Delta says they need to see
high dv/dt to initiate the arc.
If you ramp the voltage slowly then they don't seem to do anything.
Perhaps this is why Sandia changed their mind.

If you open up a Delta you see some a solid copper wire in the middle of a
coaxial copper tube.
Two or three sets depending on unit, i.e. LA602, LA603
I think this is basically a spark gap arrestor in Silicon sand that melts to
dissipate the arc energy.
I remember hearing that you were not supposed to use a spark gap arrestor
with DC unless you had supplementary MOV's, TVS's, etc. to clamp off the
voltage after the big hit.

The problem is that DC does not have zero crossings to extinguish the arc.
Once an arc forms it takes far less voltage to keep it going and so the
array could theoretically keep it going until the sun went down.

I think the best approach is staged protection connected to a LOW INDUCTANCE
path to ground.
I like very fast, low power devices(TVS) right next to critical components
then slower, higher power devices as you move out towards the surge source.

Something like this:

Component >> TVS >> inductance >> MOV or ZNR >> inductance >> SOV or spark
gap >> source of surge.

If you have any questions or I can be of any further assistance please do
not hesitate to contact me.

Best regards,

John Berdner

SMA-America, Inc.
20830 Red Dog Road
Grass Valley, CA  95945
Tel: 530.273.4895
Fax: 530.274.7271




-----Original Message-----
From: Kent Sheldon [mailto:kentsheldon at tracetec.com]
Sent: Friday, May 18, 2001 9:31 AM
To: RE-wrenches at topica.com
Subject: SOV/MOV protection devices [RE-wrenches]


What is the group feeling on surge protection devices for PV systems? I
personally have had terrible luck with MOVs. They generally fail and destroy
everything they were supposed to protect. A couple of years ago Sandia
released a report recommending the Delta SOV devices for PV systems. Now I'm
hearing that they no longer recommend Delta. Any thoughts?

Kent Sheldon
Product Manager - Photovoltaic Systems
Distributed Industrial & Utilities Markets
Xantrex Technology Inc.
Direct 925 245 5463 - Fax 925 245 1022
kentsheldon at tracetec.com  www.xantrex.com



- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com


- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

==^================================================================
EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9
Or send an email To: RE-wrenches-unsubscribe at topica.com
This email was sent to: michael.welch at homepower.com

T O P I C A -- Register now to manage your mail!
http://www.topica.com/partner/tag02/register
==^================================================================




More information about the RE-wrenches mailing list