DESIGN
MILE has a typified design so that the arrangement of equipment and instruments in the panel represents the mainstream concept of switchgear specified by most customers worldwide. In addition to draw-out units at a central location and make-type earthing switches, the design is considerably augmented to provide exceptional safety, absolute reliability and top performance.
MILE is created for straightforward manufacturing. No turning, grinding or cleansing is necessary. No jigs or welding processes are required for assembly. The enclosure is made of corrosive resistant hot-dip galvanized metal sheets. Its design allows fast assembly with rivets and screws only.
The compartment is of a detachable design for easy and convenient handling during transportation and erection on site. It is segregated with earthed metal partitions and has ample space for multi-functional protection relays, energy meters, lighting, heating and many other devices.
Fully segregated by earthed metal partitions and having its own pressure relief channel, the VCB compartment houses the bushing insulators containing fixed contacts for the connection of the circuit breaker to the busbars and the cable compartment. The bushings are covered by automatic metallic shutters. All safety interlocking mechanisms required for safe and reliable operations of the VCB, an emergency trip push-button, two inspection windows for mechanical position indication: one for VCB and the other for draw-out unit mechanisms; are fitted into the compartment. The VCB is mechanically and electrically interlocked with the compartment door so that the door cannot be opened until the VCB is turned off and racked out to the test position. For extra safety, the tool orifice to the racking in/out mechanism is equipped with a shutter operated by a keylock.
Individually operated earthed metallic shutters are automatically driven during the movement of the VCB from the test to the service position and vice versa. The busbar and cable shutters can be separately padlocked in the open position to prevent accidental contact with any live parts.
The busbar system is made of electrolytic copper and totally enclosed in its own earthed metal compartment with a pressure relief flap on the top. The busbars are connected to the fixed contacts of the upper bushing insulators by means of branch connections. Optionally, the busbars and the branch connections can be completely insulated. The busbar compartment of each panel is segregated from the adjacent busbar compartments with through insulators.
The gas exhaust duct accommodates all three pressure relief flaps and is mounted on the top of each panel. It runs along the whole length of the switchboard. The pressure generated by the internal arc makes a pressure relief flap open thus allowing hot gases to run into a special chimney to be evacuated to dedicated areas.
To facilitate maintenance, cast resin CTs are fitted onto a pivoting plate. The fixing points of the plate can receive a wide range of CTs of different brands. Two sets of CTs can be installed on a panel for distance or differential protection.
VTs with replaceable primary fuses and a striker system can be mounted on central or lower draw-out units. The striker system is intended for sending a signal about a blown fuse into the SCADA system. Optionally, fixed or top installations of VTs are available.
The make-type ES is equipped with a mechanical position indicator that can be viewed through the inspection window on the cable compartment door. An additional mechanical position indicator is located in the ES operating mechanism. The ES can be operated manually from the front of the panel or by an electrical motor via SCADA. The ES is mechanically and electrically interconnected with the VCB and the cable compartment door to provide exceptional operator safety.
Single and three-core cables up to a maximum of 7 per phase and up to 4 cables when a VT draw-out unit is installed, can be used depending on the rated voltages, panel dimensions and cable cross section. Cables are terminated with compression lugs onto copper tails and fixed by cable glands.
Made of 10x30mm electrolytic copper, the earthing bar runs along all adjacent panels and connects to the main earthing bar of the substation. All current carrying parts are interconnected with each other for equipotential bonding to guarantee personal safety against electrical shock.