Functional division of LV installation systems and their architecture: general principles

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Once we have clearly identified the main differences between Universal and Functional LV Panels, we will concentrate on the Functional ones. Since we decided that we want an LV Functional Panel, we have to start by defining what these functions are. These functions are of two types:

  • Functions related to Electrical Distribution.
  • Functions related to the Panel considered as an Installation System.

What are the ED functions?

  • Power Incomers, coming from a transformer, from a generator or from an upstream Panel.
  • Power Outgoing, to feed lighting, sockets, motors, feeder for downstream panel, etc.
  • Miscellaneous functions like measurement devices, power factor correction, etc.

What are the functions related to Installation System itself?

  • The distribution of Power and Control among the functional units. They can take different forms like centralised, splitted, bus, etc.
  • The management of the Power Cables or Busways.
  • The various supporting elements, like the frame, the fixing parts, etc.
  • The management of the internal environment. Primarily, the mastering of the thermal conditions, as well as the electromagnetic interferences (EMI) in order to achieve complete electromagnetic compatibility (EMC). But also other important aspects like the ingress protection degree (IP Code) and the degree of protection against mechanical impacts (IK Code).

How will all these functions determine the panel modularity?

The ED functions will translate to Functional Units (FU) and the installation system functions will translate to rules guiding the structural modularity.

panel modularity 2  panel modularity

panel modularity 3Intelligent devices related to a specific ED function will be installed inside of or next to the corresponding FU (e.g. the HMI of a motor starter).

Intelligent devices related to the Panel as a whole would be installed next to the power incomers (e.g. power meters, automatic transfer switches – ATS –, data loggers, communications gateway, and the like).

What are the intrinsic benefits of functional modularity?

One of the main benefits is the “readability” of the panel. The correspondence between the electrical single line diagram and the physical panel becomes evident, thanks to a logical and clever positioning of all components and devices.

A collateral benefit of functional modularity is that it can provide a dedicated area for each person according to his responsibility and skills:

  • The panel builder à Installation components and power connections.
  • The contractor à External connections (cables and busways).
  • The operation and maintenance staff à Control connections)

LV panels architecture: general principles

  • The same principles apply to all functional enclosures, whatever their size or their type of mounting (floor-standing or wall-mounted).
Floor standing and wall-mounted LV panels
  •  All functional units (FU) are independent from each other. Choices made on one of them do not impact the others in any way. This is necessary in order to maximise flexibility during assembling, operation and maintenance.
  • Each FU is closed by a front plate, removable from outside, with front access. The front plate is necessary in order to ensure the FU independence as well as to prevent access to living parts by an unskilled person.
  • There are two different cases possible:
    • An FU is installed behind a door, whether a full door or a partial one (this will be mostly the case of a fixed-mounted FU):
      • The FU must be completely independent from the enclosure.
      • Once the door opened, the front plate must be removable without the need to remove the whole FU.
      • The distance between the front plate and the door must be sufficient in order to allow fixing of devices on the front plate and on the door. Typically, this distance is not shorter than 50mm.
    • An FU is installed without any door (this could be the case of a withdrawable FU):
      • The front plate of the FU is part of the enclosure, and as such, it must comply with all the mechanical constraints of the enclosure.
      • The whole FU could be removed with its front plate.
Functional units behind a door

Writtent by Frederic Waterlot and Daniel Barstz