Trip Unit Testing Question
Trip Unit Testing Question
(OP)
We are installing a set of 208V switchgear with electronic trip breakers. We brought in a testing company to test all of the breakers, and to set the timing.
Our direction was to set the Long Time trips at 1.0 and all other settings at minimum. However, there was a misunderstanding, and the Long Time setting was also set at a minimum (0.4).
Clearly this won't work, because our breakers will now trip at 400A rather than 1000A as required.
My question is this: Are the secondary injection tests they performed on the trip units still valid if we adjust the Long Time pickup to 1.0, or should they be retested?
Our direction was to set the Long Time trips at 1.0 and all other settings at minimum. However, there was a misunderstanding, and the Long Time setting was also set at a minimum (0.4).
Clearly this won't work, because our breakers will now trip at 400A rather than 1000A as required.
My question is this: Are the secondary injection tests they performed on the trip units still valid if we adjust the Long Time pickup to 1.0, or should they be retested?






RE: Trip Unit Testing Question
That is not good.
That is even worse!
Get someone experienced in design, system analysis and coordination study to review your electrical system.
Rafiq Bulsara
http://www.srengineersct.com
RE: Trip Unit Testing Question
RE: Trip Unit Testing Question
Rafiq Bulsara
http://www.srengineersct.com
RE: Trip Unit Testing Question
Someday soon I hope to get my Electrical license - so that I can be clueless in three fields. ;)
They need to change the site so I can have my ID say "cslater (Clueless)".
Thanks for the help rbulsara. Appreciate it.
RE: Trip Unit Testing Question
You can change your "type" by emailing to the site management using the "contact us" at the bottom of this page.
Btw, I am clueless about many things too and I engage professionals in those field to do their job. I respect profession of other trades as much as I do mine.
Rafiq Bulsara
http://www.srengineersct.com
RE: Trip Unit Testing Question
Ideally, you would re-test the breakers and trip units at the new settings. But in reality, these type of changes (not this extreme normally) are commonly made without re-testing. If it on an interim basis while a complete coordination study is being completed, I'd be OK with it, since it has been verified that the trip units and breakers are functional and within tolerances for one group of settings.
But the NETA folks may not agree.
David Castor
www.cvoes.com
RE: Trip Unit Testing Question
Primary injection method is the the proper testing. I would use secondary injection method for subsequent changes like these.
I agree that minor tweaks are OK, without retesting.
Rafiq Bulsara
http://www.srengineersct.com
RE: Trip Unit Testing Question
Alan
"The engineer's first problem in any design situation is to discover what the problem really is." Unk.
RE: Trip Unit Testing Question
As far as testing at different settings, no real rule on this, settings are changed all the time, but the most likely failure for most trip units (No idea what type you have) is to fail to the minimum setting, so if you tested them at the minimum set points you really don't know if they work or not. And with secondary injection testing you don't know if your CT's are functioning.
RE: Trip Unit Testing Question