What Is Origin of the Electrical Installation? Definition, Features

Definition.

Origin of the electrical installation: point at which electric energy is delivered to the electrical installation [this term is defined in the IEC 60050-826:2022].

Note: An electrical installation may have more than one origin.

Origin of an installation: The position at which electrical energy is delivered to an electrical installation [this term is defined in the BS 7671].

The term “origin of the electrical installation” is used in regulatory documents to refer to the location through which any utilities are brought into a building, structure, or other object from the outside. In most cases, the electrical installations of building are connected to a low-voltage electrical distribution network. Therefore, the electrical power enters the electrical installation of a building from the outside.

Features

The distribution network is a low-voltage electrical network, which usually consists of a transformer substation and an overhead or cable distribution line. The distribution line starts at the low-voltage switchgear of the transformer substation and ends at the input terminals of the switchgear installed in the building.

The distribution line may also terminate at the terminals that connect the branch conductors from the overhead line to the inlet cable of the electrical installation of a building.

Depending on the specific conditions, the electrical installation of a building can be connected to the electrical distribution network either by means of a distribution line cable or by means of an input cable. The place through which the cable is routed is called the origin of the electrical installation of a building. The electrical circuits start at the origin of the electrical installation of a building.

The boundary that separates the electrical distribution network and the electrical installation of a building connected to it usually runs:

  • On the MDB input terminals, if the electrical installation of a building is connected to the underground cable of the electrical distribution network;
  • On MDB input terminals, if the electrical installation of a building is connected to the overhead line of the electric distribution network, and the branch from the overhead line to the input and the origin to the electrical installation of a building is performed by cable, insulated wires or self-supporting insulated wires;
  • on the terminals connecting the wires of the overhead line branch to the input with the cable (wires) of the origin of the electrical installation of a building, if the electrical installation of a building is connected to overhead line of the electric distribution network, and the branch from overhead line to the input is performed with uninsulated wires.

Examples:

TN-C-S system single-phase, 2-wire where the PEL conductor is separated into the protective conductor and the earthed phase conductor at the origin of the electrical installation
Figure 31B4 – TN-C-S system single-phase, 2-wire where the PEL conductor is separated into the protective conductor and the earthed phase conductor at the origin of the electrical installation
TN-C-S system single-phase, 2-wire where the PEN conductor is separated into the protective conductor and the neutral conductor at the origin of the electrical installation
Figure 31B3 – TN-C-S system single-phase, 2-wire where the PEN conductor is separated into the protective conductor and the neutral conductor at the origin of the electrical installation

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