Substations
Package substations
A ring main unit, a transformer and a low voltage cabinet close coupled on a common base, installed outdoors without a separate building.
At a glance
- Arrangement
- close coupled on a common baseno connecting cables between units
- Placement
- outdoors on a plintheach unit carries its own weather protection
- Medium voltage
- ring main unitconfiguration set by the network
- Transformer
- liquid immersed, commonly
- Low voltage
- cabinet with incomer and outgoing waysset by the loads
A package substation joins the ring main unit, the transformer and the low voltage cabinet directly to one another on a common base. The close coupling removes the interconnecting cables and the building from the site works, which leaves a foundation, the incoming and outgoing cables and the earthing to be prepared.
Because there is no building, each unit relies on its own enclosure for weather protection, and the arrangement is exposed in a way a prefabricated station is not. Where security, appearance or climate argue for an enclosure, a compact substation or a separate housing is the usual alternative.
What gets specified
| Parameter | Typical options | What decides it |
|---|---|---|
| Ring main unit | Configuration and insulation medium | The network arrangement and destination rules |
| Transformer | Rating and voltage pair | The load |
| Low voltage cabinet | Incomer and outgoing ways | The loads supplied |
| Base and coupling | Common skid or plinth, flange coupling between units | The manufacturer's arrangement |
| Enclosure protection | IP rating of each unit | The installed position |
| Housing | None, or an optional surround | Security, appearance and climate |
Typical options are the ones buyers most often specify. They are not a list of what is available, which is confirmed per enquiry.
Applicable standards
| Standard | What it covers |
|---|---|
| IEC 62271-200 | Metal enclosed switchgear above 1 kV up to and including 52 kV, for the ring main unit |
| IEC 60076-1 | Power transformers, general requirements |
| IEC 61439-1 and IEC 61439-2 | Low voltage switchgear assemblies, for the low voltage cabinet |
| IEC 60529 | Degrees of protection provided by enclosures |
The standard that applies is set by the specification and the destination market. Editions change, so the edition cited in a specification is confirmed in the quotation.
Documents normally requested
| Document | What it evidences |
|---|---|
| Technical datasheet and single line diagram | Ratings, panel functions and the arrangement offered |
| General arrangement drawing | Footprint, height, cable entry and floor fixings |
| Type test report | The design has passed the type tests of its standard, including internal arc where claimed |
| Routine test report | The individual assembly's tests before dispatch |
| Schematic and wiring diagrams | Control, protection and interlocking circuits |
| Operating and maintenance manual | Operation, interlocks and maintenance |
An internal arc classification is only as good as the type test behind it, and it applies to the tested configuration. Ask for the report that matches the arrangement offered.
What we need to quote accurately
| 01 | Transformer rating and the primary and secondary voltage |
| 02 | Medium voltage configuration: ring main unit functions or panel schedule |
| 03 | Low voltage distribution: incomer rating, number and size of outgoing ways |
| 04 | Enclosure type and whether it is operated from outside or from an internal aisle |
| 05 | Site access for delivery and lifting, and the foundation arrangement |
| 06 | Metering position and any network operator requirement |
| 07 | Quantity, destination, required delivery date and acceptable condition |
Delivery and logistics
Distribution equipment is heavy, and a delivery date is only real once the site is ready for it. The dimensions and weight of the unit offered decide the vehicle, the lifting equipment and the route to the foundation, and they come from the manufacturer's drawing rather than from the rating.
Liquid immersed transformers are usually shipped filled, which affects transport rules and the handling on arrival. Anything crossing a border also carries customs documentation, and where the destination applies its own conformity or energy efficiency rules the paperwork has to match that market rather than the country of manufacture.
Lead times vary widely with rating, specification and manufacturer loading. We state a delivery basis in each quotation for the specific unit offered and do not publish a general lead time we cannot hold.
Related
Request a quote for this equipment
Send the rating, the voltage and the destination, or submit the specification, drawing or nameplate. Anything missing is raised before it reaches a supplier.