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4. PT Protection Settings
4.7 Making Current Release (MCR)
The PT trip unit has a Making Current Release (MCR)
function. This safety feature prevents the circuit breaker
from being closed and latched-in on a faulted circuit. The
MCR is enabled only for the first two cycles of current
following the initial circuit breaker closing operation.
The circuit breaker will trip with no delay and the
instantaneous ("INST") indicator will show the cause of
trip.
This non-adjustable release is set by the frame module
of the circuit breaker. Refer to time current curves for
specific values.
4.8 Event Recording and Waveform Capture
The PT trip unit will record information surrounding
events, alarms, and trips into a set of logs. For simple
events, only the reason and a time-stamp (based on the
trip unit's real-time clock) are stored. More important
events additionally store a snap-shot of real-time values
(currents and voltages). The most important events
additionally store more information, storing waveforms of
current and voltage experienced during the event.
Each log can store a set number of events and is
managed as a first-in first-out buffer (FIFO). As the
information is stored for the most recent event, the
information from the oldest event is eliminated.
Figure 11. Event Recording Screen
4.9 Circuit Breaker Health Diagnosis
The PT unit includes an algorithm to monitor the health
of the circuit breaker. The parameters monitored by
the algorithm include short circuit, overload, operation,
temperature, and operating time. The combination of
all these parameters provides an overall picture of the
circuit breaker condition and can be used for preventive
maintenance and improved system reliability. This health
monitoring algorithm is a tool and cannot be used to
replace established circuit breaker maintenance or
replacement.
The health monitor feature consists of index that track
the cumulative service performed by the circuit breaker.
The index starts from zero and increases to 10,000 points
depending on the conditions under which the circuit
breaker operates. The index remains in the frame module
of the circuit breaker. Changing the trip unit does not
change the accumulated points, which means the values
cannot be reset.
8
PT 10 TrIP UnIT User ManUal Power TrIP (PT) UnITs MN013021EN January 2024 www.eaton.com
The health alarm threshold ranges from 0% to 50%,
with the adjustable step of 1%. The health values can be
viewed through the PTM software.
Figure 12. Circuit Braker Health Diagnosis
Note: Circuit breakers that operate under normal
N
ote:
conditions and report a health percentage of less
than 100% have a cumulative service life within
their normal service life. Regular maintenance
should be carried out during this period, and
if there are no signs of abnormal or excessive
wear, damage or adverse environment, the circuit
breaker is considered suitable for continued use.
When the health percentage approaches zero, the
circuit breaker should be carefully evaluated to
determine its suitability for continued use. Based
on the accumulated usage history, the circuit
breaker may reach the end of its normal service
life and should be carefully inspected to determine
the required operation. It is best practice to plan
the replacement of circuit breakers based on the
condition of the circuit breaker, the maintenance
performed, and your site-specific maintenance
guidelines and standards.
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