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Electrical connections

Connecting the power cables

In low voltage electrical installations, the laying of pipes and the making of connections obey very precise rules of the art described in the NF C 15-100 standard and in the UTE C 15-520 guide.
The connections of the electrical conductors must be made exclusively either by appropriate connection devices such as terminal strips, distributors, terminal blocks, or on the terminals of the apparatus. The connections of each of the protective conductors to the main protective conductor must be made individually.


  • Pour la protection des personnes, il faut raccorder en premier lieu le conducteur de protection du tableau à la prise de terre.
  • Brider les câbles au plus près des connexions pour ne pas créer de contraintes mécaniques sur les plages des appareils.
  • Lorsqu’on n’utilise pas de presse-étoupes, brider également les câbles au plus près de l’entrée dans l’enveloppe électrique (boîtier, coffret, armoire…).
  • Les câbles ne doivent jamais circuler au contact ou entre des conducteurs actifs.
  • Les arêtes vives de l’ossature de l’enveloppe situées sur le passage des câbles doivent être protégés pour éviter de blesser les conducteurs.
  • Respecter un rayon minimum de courbure de 6 à 8 fois le diamètre extérieur du câble.
  • Tous les raccordements de puissance doivent être réalisés avec de la visserie classe 8.8 et rondelle contact élastique, et serrés au couple à l’aide d’une clé dynamométrique.
torque wrench
  • When connecting aluminum cables to copper pads, bi-metal interfaces or lugs must be used to avoid any form of galvanic corrosion.
  • Make strands by separating the different types of circuits (power, control, 48V, 24V, direct, alternating, etc.) to avoid interference by electromagnetic fields, between weak currents and strong currents.

Realization of strands

Realization of strands

Strand clamping

Strand clamping

For cable sections> = 50 mm², use 9 mm wide hoops.

Tightening torque

Recommended tightening torques for mechanical and electrical connections with class 8.8 screws:

Tightening torque

Class 8.8 :

Class 8.8

Cable connection from above

  • Remove the roof.
  • Make the holes for mounting the cable glands or grommets.
  • Fit the cable glands or grommets. They must comply with the protection degree of the switchboard (IP: NF C 20-010).
  • Raise the roof.
  • Pass the cables through the cable glands or grommets.
  • Pass the cables through the compartments provided for this purpose, and clamp them on the cable clamping supports every 400 mm. – Crimp the terminals and connect.

When the waterproofing does not require cable glands or is achieved using foam, the cables can pass through a rectangular cutout in the roof. Be careful, this method is often the simplest but requires special care to fill the cut as well as possible after passing the cables (risk of short circuits over time by dirt, introduction of rodents, etc.)

Cable connection from above

Cable connection from below

For passage through a 2-part cable gland plate, it is not necessary to make any drilling, the cable gland plate prevents the creation of induced current.
The cables are protected by a polyurethane foam gasket which ensures tightness.

For passage through a cable gland plate

For passage through a solid cable gland plate

  • Remove the bottom plate.
  • Make the holes for mounting the cable glands or grommets (the cutout limit for solid cable gland plates is at least 30 mm from the edge of the plates).
  • Fit the cable glands or grommets. They must respect the degrees of protection (IP: NF C 20-010).
  • Refit the bottom plate.
  • Pass the cables through the cable glands or grommets.
  • Pass the cables through the compartments provided for this purpose, and clamp them on the clamping supports every 400 mm.
    When not using cable glands, it may be easier to prepare the cable heads outside the switchboard (crimping the lugs for example), and to tip them inside the enclosure after have removed the lower removable side member (if it exists).
For passage through a solid cable gland plate

Connection on bar tails

  • Check that the circuit identification matches that of the device.
  • In the event of connection on bus tails with several bars per phase, position the terminals opposite each other and insert copper shims.
  • Respect the insulation distances between phases: 14 mm minimum (according to IEC 60439-1).
  • Mark all nuts and bar tails with a dot of varnish after tightening to the recommended torque.
Connection on bar tails

Connection to the device ranges

  • When the connection is made directly to the device pads, comply with the tightening torques given by the device manufacturer.
  • Check that the length of the screws supplied with the device is compatible with the thickness of the terminals to be connected.
  • Respect the safety perimeter around the devices, defined by the manufacturer and guaranteeing their correct functioning.
  • If necessary, replace the phase separators and terminal shields after connection.

Cable heads

The sealing of the cable heads must be achieved with shrink sleeves, heat-shrink …
The terminals must be protected by rubber sleeves, heat-shrinkable sleeves … (and not by the use of electrician’s tape which is only used for color marking).
The cables must be marked with a captive system.

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