Functions of a substation with LV metering: Difference between revisions
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*Dry-type, vacuum-cast-resin transformers for locations inside premises, e.g. multistoreyed buildings, buildings receiving the public, and so on... | *Dry-type, vacuum-cast-resin transformers for locations inside premises, e.g. multistoreyed buildings, buildings receiving the public, and so on... | ||
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| valign="top" align="left" | (1) Polychlorinated biphenyl | | valign="top" align="left" | (1) Polychlorinated biphenyl | ||
Revision as of 08:53, 17 August 2012
A consumer substation with LV metering is an electrical installation connected to a utility supply system at a nominal voltage of 1 kV - 35 kV, and includes a single MV/LV transformer generally not exceeding 1,250 kVA.
The different functions of the substation are:
The substation
All component parts of the substation are located in one room, either in an existing building, or in the form of a prefabricated housing exterior to the building.
Connection to the MV network
Connection at MV can be:
- Either by a single service cable or overhead line, or
- Via two mechanically interlocked load-break switches with two service cables from duplicate supply feeders, or
- Via two load-break switches of a ring-main unit
The transformer
Since the use of PCB(1) - filled transformers is prohibited in most countries, the preferred available technologies are:
- Oil-immersed transformers for substations located outside premises
- Dry-type, vacuum-cast-resin transformers for locations inside premises, e.g. multistoreyed buildings, buildings receiving the public, and so on...
| (1) Polychlorinated biphenyl |
Metering
Metering at low voltage allows the use of small metering transformers at modest cost.
Most tariff structures take account of MV/LV transformer losses.
LV installation circuits
A low-voltage circuit-breaker, suitable for isolation duty and locking off facilities, to:
- Supply a distribution board
- Protect the transformer against overloading and the downstream circuits against short-circuit faults.
Simplified electrical network diagram
The diagram (Figure B10) shows:
- Methods for connecting to the network (4 options):
- Spur network or single-line service
- Provisional network (can be transformed into a loop)
- Parallel feeders service
- Loop or ring-main service
- MV protection and MV/LV transformation methods
- LV metering and LV general isolation methods
- LV protection and distribution methods
- Zones accessible to different parties
Fig. B10: Consumer substation with LV metering
