Using the small sample of MCCBs removed from service at
the paper mill facility as a result of this initiative, it’s possible
to calculate some measure of overall reliability of the MCCBs
in this facility. Thermal imaging is conducted twice per year for
each MCCB installed in the mill. Of 11 breakers removed from
service in the Paper Machine #3 and Deink area during the
course of one calendar year, only 5 that were returned and
tested at the PIC exhibited temperature rise levels above the
50oC test standard. This represents 0.57% of the 876 total
MCCBs installed and operational in this area of the mill.
Speaking to the 6 breakers that passed design tests at the
PIC but were removed from service by the mill, it’s likely that
supporting electrical systems for these breakers were the root
cause of elevated temperature readings in the field. For
instance, tightening a MCCB terminal that is corroded or has
oxidized will have little affect in reducing elevated surface
temperature readings following an IR scan. Also, review of the
mill IR survey data shows that only 4 of the 11 breakers
actually exhibited hot spot operating temperatures exceeding
the 130oF threshold identified in the IEEE 1458 Standard. This