Trip-Free Operation of Medium Voltage Circuit Breakers
Definition and Behavior
The trip-free operation of medium voltage circuit breakers ensures that, regardless of any closing command, the breaker will open if a tripping signal (either mechanical or electrical) is received. This characteristic guarantees safe and reliable operation under all conditions. The behavior of the circuit breaker under different scenarios is detailed below:
Simultaneous Closing and Tripping Signals:If a closing operation is in progress and a tripping signal is received simultaneously, the circuit breaker contacts are permitted to close momentarily before opening.
Auxiliary Switch Contacts in Trip Circuit:If the trip circuit employs auxiliary switch contacts of the circuit breaker or equivalent contacts, the trip coil cannot be energized until these contacts in the trip circuit are closed.
Mechanically Initiated Tripping Command:If the tripping command is initiated mechanically (manually) and held in the actuated position before a closing signal is applied, the main contacts of the circuit breaker are not allowed to close, even for an instant.
Closing Signal Before Tripping Signal:If the closing signal is initiated before the tripping signal, the circuit breaker contacts are permitted to close momentarily before opening.
Illustrative Example
The Eaton trip-free MV circuit breaker operation table visually demonstrates these operational principles, providing a clear reference for understanding how the breaker responds under various conditions.
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