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PT UNIT USER MANUAL
APRIL 2023 www.eaton.com.cn
4. PT Protection Settings
4.10 Event Recording and Waveform Capture
The PT 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,
for example, storing waveforms of current and voltage
experienced during the event.
Each log can store a set number of events and is managed in
a first-in first-out manner (FIFO). As the information is stored
for the most recent event, the information from the oldest
event is eliminated.
4.11 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.
The health of the circuit breaker is represented by the health
percentage calculated by the index. A new circuit breaker
reports 100% health corresponding to 100% remaining
service life.
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. These values can also be viewed
on the screen for PT20/25 devices.
Note:
The health percentage can be mapped to a configurable
relay.
Circuit breakers that operate under normal 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.
