[RE-wrenches] UPS disturbance with SMA Inverters

Glenn Burt glenn.burt at glbcc.com
Mon Aug 4 10:03:44 PDT 2014


I wonder if the UPS is grumbling about high voltage as the inverters push back current...

Glenn 

-----Original Message-----
From: "Carl Adams" <swingjunkie at gmail.com>
Sent: ‎8/‎4/‎2014 10:29
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Subject: [RE-wrenches] UPS disturbance with SMA Inverters

Hello Wrenches,

I have a site which is experiencing nuisance disturbance of the computer
UPS systems at the site.  The site owner "suspects" this is due to the PV
system which is a 50 kW system using 6 SMA SunnyBoy inverters.  The
nuisance disturbance is a clicking noise in the UPS units.  The disturbance
is not enough to cause the UPS to engage, so it seems to be a small
disturbance on the AC power.   The site owner "suspects" the inverters are
the source of this disturbance since 1) It seems to only occur when we have
a good solar day.  2) If the inverters are shut down the problem goes away,
and if you start up the inverters the problem exhibits again.

The site was commissioned in March of 2012 and has had no problems till
this issue last month.  In reviewing the event log on Sunny Portal there
are no inverter anomalies.  SMA tech support had not run into this issue
and had no ideas, they too agree the inverters are not reporting any
anomalies.

The problem is not persistent but rather intermittent making this harder to
troubleshoot.

So my questions are
1) Has anyone else seen this sort of issue before, related to SMA SunnyBoy
inverters.
2) Can you recommend an AC power monitoring tool which would support
 frequency and voltage monitoring on the AC line.  Perhaps one data set on
the circuit feeding the computers and another on the inverter output
circuit.

For clarity the six SunnyBoys feed into an AC Combiner panel which backfeeds
into the building main distribution panel.  The service is 240V single
phase.

With Regards
Carl Adams, SunRock Solar
NABCEP Certified PV Installer
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