Choice of MV equipment

Standards and specifications

Switchgear and equipment shall conform to the following international standards:
IEC 62271-1, 62271-200, 60265-1, 62271-102, 62271-100, 62271-105
Local regulations may also demand conformance to national standards. These include:

• France: UTE
• United Kingdom: BS
• Germany: VDE
• USA: ANSI

Choosing types of equipment

Substations can be implemented in line with local standards and practices using equipment such as:

• Modular units to support all types of layout and any subsequent expansion work (whilst ensuring there is sufficient space)
• Compact arrangements based on the ring-main unit where the supply is provided via a loop (single assembly comprising 3 functions). These are particularly suitable where:

  - Climatic conditions and/or pollution are very bad (integrated insulation)
  - There is not enough space for a modular solution

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Fig. B11: SM6 modular unit

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Compartmentalised modular units in metallic enclosures

IEC 62271-200 standard
The IEC 62271-200 standard specifies «AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV».
The main precepts of the standard relate to:

• Switchgear types:

  - AIS (Air Insulated Switchgear)
  - GIS (Gas Insulated Switchgear)

• Functional units: «a switchgear component contained in a metallic enclosure and incorporating all the main and auxiliary circuit equipment required to perform a single function» - usually a modular unit
• Compartments: «a switchgear component contained in a closed metallic enclosure (apart from the openings required for interconnection, control or ventilation)». The manufacturer defines the content (e.g. busbar, cables, switchgear, etc.) and the number of compartments able to house the following types of switchgear:

  - Fixed
  - Removable

• Accessibility of individual compartments:

  - Controlled by interlocking or in accordance with procedures; for compartments which can be opened during normal operation
  - Using tools; for compartments which should not be opened during normal operation
  - Zero; for compartments which must not be opened

• The LSC (Loss of Service Continuity) defining the extent to which other compartments can remain energised when one compartment is open

  - LSC1, when opening a compartment requires the other functional units to be de-energised
  - LSC2 A, when the other functional units can remain energised
  - LSC2 B, when the other functional units and all the cable compartments can remain energised
  - The partition class between energised components and an open compartment, based on the type of partition: «a switchgear   component contained in a metallic enclosure and separating one compartment from another»:
  - PM: metallic partitions
  - PI: insulating partitions