The voltage metering panel measures the busbar voltage and carries that information to the protection and metering circuits. After the disconnector comes the medium voltage fuse, then the voltage transformer, whose other terminal is connected to earth.
The voltage transformer steps the medium voltage down to a safe, standard value on the secondary side. That secondary voltage is used as a common reference by energy meters, synchronisation relays, voltage protection relays and indicating instruments.
The duty of the fuse is to protect the busbar in the event of a fault in the voltage transformer. A voltage transformer is a low-rated device; if a short circuit occurs on its secondary side, the fuse operates and prevents the fault from reaching the busbar.
The panel is not connected in series with the main circuit — it takes a branch from the busbar. It therefore carries no load current and can be built narrower than the standard panel section.
