LT panels or LT switchboards are designed to distribute stepped-down voltage to power equipment and control panels.
They typically consist of moulded case circuit breakers (MCCBs), power contactors (PCs), protective relays (PRs), meters, indication lamps, control switches, etc.
A. MCCB
An MCCB is designed to “open/close” low voltage feeder circuit or branch circuit at normal condition. It also breaks the circuit automatically in case of abnormal condition such as overload, short circuit, etc.
B. Power Contactor
A power contactor is typically used for “on / off” control of motors.
A relay can be installed on the circuit for overload protection. Electromagnetic force works to “open /close” the contacts.
The O&M checks to be made are as follows:
• Check for abnormal noise or overheating of exciting coils, abnormal noise and discolouration of contacts (carbonized or worn contact surfaces by arcing)
• Check for the proper working of all display indicators like voltmeters, ammeters, energy meters and indicator lamps
• Check whether the name of the panel is written on it and it is correct as per the SLD
• Check for the proper earthing of the panels