Definition:
The definition of mobile substation or portable substation is a completely self-contained trailer-mounted substation consisting of a transformer, cooling equipment, high voltage switchgear, and low voltage switchgear along with metering, protection relaying devices, AC and DC auxiliary power supply, surge protection, and cable connecting arrangement.
The mobile means something is portable, or it can be moved geographically from point to point. A substation on the other hand is a site where electricity supplied by generation plants is transformed and/or controlled for distribution. A mobile substation is therefore a movable electricity transformation and control system. Its mobility can be achieved by road, rail, sea, or air. For road transport (which is the most common), it is mounted on a container or a trailer that is attached to a truck engine to move it.
It’s mostly used by utilities and industries to provide a temporary power supply in an area that is not supplied by the grid. In these cases, constructing one permanent outdoor or indoor substation for the fulfillment of the power supply is not economical. Also, a mobile substation is required where there is a lack of space for constructing an outdoor substation during any big construction work when the consumption of huge power by construction machines is required.
Mobile substations are also used to quickly restore electrical service during an outage caused by a storm or other disaster. This can also provide temporary power service during the construction of permanent facilities. It also can be used as an alternate power service during regular maintenance of existing equipment.