This section lays out the major performance requirements for the MCCB (moulded-case electrical circuit breakers) installation inside switchboards.
All moulded-case circuit breakers shall comply with IEC 60947-2.
All electrical MCCB shall be of moulded insulating material of good mechanical strength and non-tracking properties. The tripping mechanisms shall be calibrated in compliance with IEC standards at the factory and the breaker shall be sealed to prevent tampering.
The MCCB shall be so designed that when on tripped condition, the circuit breaker cannot be switched on unless it has been reset by switching it to the OFF position first. The operating condition (i.e. ON, OFF or TRIP) of the circuit breaker shall be clearly indicated. The construction and operation of the MCCB installation shall be such that if a fault occurs, all the poles of the breaker shall operate simultaneously to isolate and clear the fault efficiently and safely without any possible risk to the operator or to the installation.
Each MCCB shall incorporate a ‘trip-free’ mechanism to ensure the breaker cannot be held closed under fault conditions. The operating mechanism of the circuit breaker shall be hermetically sealed at the factory and all metallic parts associated with the operating mechanism shall be treated against rust and corrosion.
Bolt-in type solid neutral links shall be provided and fitted in the same compartment together with the phase poles.
Means shall be provided to padlock the MCCB in the ‘OFF’ position. Mechanical ‘ON/ OFF’ indicator operating in conjunction with the rotary type operating handle of the circuit breaker must be provided.
MCCBs supplying loads from switchboards connected to the emergency power system shall be provided with facilities for remote operation (OPEN and CLOSE) and auxiliary contacts for remote indication.
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