[RE-wrenches] Smart grid grid-connected compatibility

[Kent Osterberg]

Wrenches,

There weren't very many replies to my question about grid-connected 
inverter compatibility with utility remote meter reading systems so I'll 
explain my recent experience with hope that this information may be of 
assistance sometime.

Last fall I installed an Ephase system for a customer. Soon after it was 
on line he complained that the inverters were dropping off line 
frequently. Since we had a lot of cloudy weather in northeast Oregon all 
winter, it wasn't easy to see what was going on. In the spring we had 
some clear days and noticed that the inverters were dropping off line 
several times a day at exactly the same time every day. It didn't take 
very long for our suspicion to turn to the utilities new remote meter 
reading equipment. Because our weather has been so cloudy it took a 
while to find clear days where the utility could provide assistance. But 
with their help by reading the meter on demand and temporarily disabling 
the meter communications we were able to finally prove the remote meter 
reading system is tripping the inverters offline for five minutes every 
time the meter sends a data packet.

Recently the remote meter reading system has expanded to more areas so 
we have now observed this problem with both Enphase M190 and M215 
inverters. The system we've observed that is in town is seeing many more 
dropouts, so we think every kWh meter on the same service transformer 
and maybe some beyond it are causing trouble too.

The remote meter reading equipment is made by Aclara and uses their 
TWACS technology. This isn't new technology and with more remote meter 
reading systems going in all the time there will be more occurrences of 
incompatibility. Certainly more between Enphase and TWACS. And possibly 
more between other inverters and other communications systems.

At present I'm really dissatisfied with Enphase's support on this issue. 
All they've done is point out that only a few systems have been affected 
and put us in the position of telling customers that they'll just have 
to live with the lost production time. Until Enphase comes up with a 
fix, I won't install any more Enphase inverters.

-- 
Kent Osterberg
Blue Mountain Solar, Inc.
www.bluemountainsolar.com
t: 541-568-4882