ABB REF615 Applications Manual page 208

Section 8
Condition monitoring functions
202
Breaker contact travel time
High travelling times indicate the need for maintenance of the circuit breaker
mechanism. Therefore, detecting excessive travelling time is needed. During the
opening cycle operation, the main contact starts opening. The auxiliary contact A
opens, the auxiliary contact B closes, and the main contact reaches its opening
position. During the closing cycle, the first main contact starts closing. The auxiliary
contact B opens, the auxiliary contact A closes, and the main contact reaches its close
position. The travel times are 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
known 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
1MRS756378 D
y
t where the factor y is
REF615
Application Manual