Combiner panel troubleshooting

G

GrizzlyAdams

New User
Location
Marion Illinois
Occupation
Solar installation
We have 2MW site that keeps tripping 2 breakers on the combiner panel. I have been trouble shooting this issue for years. The top 2 breakers in the panel trip during spring and early summer. We have swapped the breakers around and confirmed the issue did not follow the breakers, We also moved the breakers up in the panel to create separation from the bottom 8 breakers to try and dissipate heat. I have checked all the wiring and terminations and I cannot find anything of concern, I even repulled new wire from one of the inverters. The last time we were there, we did an infrared scan and noticed B phase on the 2 breaker that keep tripping and wires are hotter than the other phases. I am hitting a mental road block on what could be causing the issue. Any recommendation on troubleshooting would be appreciated. We have another combiner panel onsite with the same number of breakers and and in the same conditions and it is not having any issues.
 
W

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Total guess, but consistent with the information provided: damage to the B-phase bus at those two locations, so the breakers there aren't making a sufficiently low resistance connection to the bus?

Cheers, Wayne
 
P

pv_n00b

Senior Member
Location
CA, USA
Occupation
Professional Electrical Engineer
I'm assuming this enclosure is outside and exposed. When I have seen this before a logging temperature recorder was used to record the temperature inside at the top of the enclosure at the level of the tripping CBs and compare that to the CB trip times. The trip times correlated to high temps in the enclosure. Leaving the enclosure door open and rigging a shade over the enclosure stopped the tripping. The long term fix was AC in the enclosure and no more approving single vertical columns of CBs in exposed enclosures.
 
S

solarken

NABCEP PVIP
Location
Hudson, OH, USA
Occupation
Solar Design and Installation Professional
Tripping in spring and early summer would suggest it is a combination of high inverter current and high ambient temp, not just primarily ambient temp. Can you confirm that from any monitoring data? Is there any difference between inverters? Did you try moving the inverter conductors to a breaker lower in the panel to see if it follows the inverter (if the wiring will reach)? If it follows the inverter, instead of being related to the breaker position, maybe it is an issue with the inverter. And what conductor sizes and material, and what inverter output current rating are we talking here?
 
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