ABB RER620 Technical Manual page 375

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RER620
Technical Manual
calculated based on the state changes of the auxiliary contacts and the adding correction
factor to consider the time difference of the main contact's and the auxiliary contact's
position change.
Operation counter
Routine maintenance of the breaker, such as lubricating breaker mechanism, is generally
based on a number of operations. A suitable threshold setting, to raise an alarm when the
number of operation cycle exceeds the set limit, helps preventive maintenance. This can
also be used to indicate the requirement for oil sampling for dielectric testing in case of an
oil circuit breaker.
The change of state can be detected from the binary input of the auxiliary contact. There
is a possibility to set an initial value for the counter which can be used to initialize this
functionality after a period of operation or in case of refurbished primary equipment.
y
Accumulation of I t
y
Accumulation of I t calculates the accumulated energy ΣI
as the current exponent. The factor y depends on the type of the circuit breaker. For oil
circuit breakers the factor y is normally 2. In case of a high-voltage system, the factor y
can be 1.4...1.5.
Remaining life of the breaker
Every time the breaker operates, the life of the circuit breaker reduces due to wearing. The
wearing in the breaker depends on the tripping current, and the remaining life of the
breaker is estimated from the circuit breaker trip curve provided by the manufacturer.
Example for estimating the remaining life of a circuit breaker
Condition monitoring functions
y
t where the factor y is known
Section 6
369