×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

CH digitrip 520M Short time too fast!

CH digitrip 520M Short time too fast!

CH digitrip 520M Short time too fast!

(OP)
Hi,

We were testing low Voltage CB with digitrip 520 M trip unit.

The short time delay setting is .5 sec, but when we test it with primary injection, the tripping delay is 60 ms.  The flag really show ST trip, not inst.  When we test the inst., the delay was 50 ms.

All the 3 breaker tested were the same.  We really were in the ST range for current.  We tried to change setting, different current, but always the same.

Does anybody experencied the same with this trip unit.

Thanks

RE: CH digitrip 520M Short time too fast!

(OP)
Forget my question, i found the answer:

Zone interlocking

RE: CH digitrip 520M Short time too fast!

Digitrips will default to the lowest setting, in this case STD. A common failure is dirt in the pots. We repair these often with the same issues.

Or, ZSI can get you.

RE: CH digitrip 520M Short time too fast!

Sorry for the late post.
520's need a jumper between B8 and B9 secondary terminals to defeat the zone interlock. Without this jumper, the time delay setting is overrided.  

RE: CH digitrip 520M Short time too fast!

I've seen problems with misalignment of the ZSI connectors on the DS-II breakers.

Alan
"The engineer's first problem in any design situation is to discover what the problem really is." Unk.

RE: CH digitrip 520M Short time too fast!

(OP)
Thank you for your replies

As i said, i found the solution, and it was as unclebob said.

The jumper was there on the craddle terminal, but when we unracked the breaker for primary injection testing, the breaker wasn't connected anymore to the craddle, so the jumper wasn't there also.

It was the first time we tested this trip unit and i tried to find a quick answer when i was on the field.  

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources