Junction And End Boxes

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Junction And End Boxes

Junction box

Description

The junction box must ensure the electrical contact, the insulation of the contacts and the sealing of the accessory in order to allow the continuity and the reconstitution of the cables in terms of insulation and mechanical protection..

Constitution

The molded version junction box mainly consists of:

A box body made of synthetic materials, comprising:

-an internal semiconductor shield and/or field distributor elements;

– an insulating envelope;

– an external semiconductor screen;

– an insulating material providing sealing, insulation and protection.

If necessary reducers to adapt the body of the box to the dimensions of the cables to be connected.

The junction box in the retractable version mainly consists of:

-one or more tubes comprising insulating or semi-conductor elements, and/or field distributor elements;

– a continuity of metal screen and external protection.

These are the following constituents:

– the web junction sleeve;

-the reconstitution of the insulation and the semi-conductor screens;

– the continuity device of the metal screen;

– the earthing device for the three-pole assemblies (if necessary); – external protection.

Boîtes De Jonctıon Et D’extrémıté Pour Câbles Souterraıns Moyenne Tensıon
Boîtes De Jonctıon Et D’extrémıté Pour Câbles Souterraıns Moyenne Tensıon3
End box

Description

The end box must ensure electrical contact, insulation of the contact part and sealing of the cable ends. The contact is ensured by lugs or crimped or punched box heads.

Constitution

Insulation is obtained by box bodies and filling with insulating material (for cast boxes) or by synthetic materials placed around the cable (for cables with synthetic insulation).

Depending on their use, we distinguish:

– the end boxes for the exterior;

– the end boxes for the interior, including those intended for the cells;

– the end boxes called “plug-in crossings” for transformer stations

The end box depends on the nature of the cable, its insulation and its section. Boxes for cells and plug-in bushings also depend on the rating of the cell or the power of the transformer supplied.

2.1- End boxes for interior and exterior:

The main components of indoor and outdoor boxes are:

  • an aluminum or copper end lug;
  • a semiconductor ribbon;
  • an earth connection;
  • a tinned copper earth braid;
  • a hoop band in stainless steel or similar material;
  • a field distributor;
  • tape or sealant;
  • external protection;
  • a silicone grease or equivalent grease if necessary.
  • possibly skirts.

The field distributor and external protection must be of the heat-shrinkable, mechanically shrinkable or slip-on type.

  1. Plug-in bushings

The main components of plug-in bushings are: an insulating casing;

  • an external conductive screen;
  • a screen for connecting the external screen to the cable screen;
  • a connecting cable for the screens;
  • a screenshot;
  • a tinned copper earth braid.
  • a stainless steel hoop strap or similar material;
  • an entry and/or sealing part;
  • an insulating jacket for the cable;
  • an external semiconductor shield;
  • an outer sheath;

 a fixing assembly on the fixed part.

Technical characteristics

Cable sections

The junction and end accessories covered by this Technical Specification must be suitable for cables governed by standards IEC 502 – 2, NFC 33220 or NFC 33223, with sections:

    – 25 -35 mm² copper;

    – 50 -70 – 95 – 120-150 – 240 mm² Aluminum.

Outdoor protection

External protection (sheath, retractable, sheath, etc.) must be provided to ensure the following functions:

– protect the screen reconstruction against corrosion; – ensure the mechanical strength;

– ensure watertightness.

Terms of use

The accessories covered by this Technical Specification must withstand the following climatic conditions without damage:
– Maximum ambient air temperature: + 55°C
-Minimum ambient air temperature: – 5°C
-Humidity rate: 90% at 20°C
-Maximum core temperature:
* In normal service: + 90°C;
* In short circuit: + 250°C;
* In short-term overload: + 120°C.

Marking

The exterior of the packaging of the accessories covered by this Technical Specification must clearly and indelibly bear the following indications:

   – the acronym, name or brand of the manufacturer;

   – the reference of the accessory;

   – a mark allowing the identification of the manufacturing batch;

   – month and year of manufacture;

   – the expiry date for the resin boxes;

   – indication of voltage Um in kV;

   – the section and nature of the cable.

Reference standards

The above-mentioned accessories must comply with the provisions of this Technical Specification and all the requirements which are not contrary thereto, provided for in the reference standards, namely:

– IEC 60 502-2: Power cables with extruded insulation and their accessories for rated voltages from 1 KV ( Um= 1.2 KV) to 30 KV ( Um=36 KV) – Part 2: Cables with rated voltages of 6 KV (Um=7.2KV) to 30KV (Um=36KV).

– IEC 60 502-4: Power cables with extruded insulation and their accessories for rated voltages from 1 KV ( Um= 1.2 KV) to 30 KV ( Um=36 KV) – Part 4: Test requirements for cable accessories with rated voltages from 6KV (Um=7.2KV) to 30 KV (Um=36 KV).

– NF C33-050: Prefabricated unipolar junctions and derivations for cables with synthetic insulation with a rated voltage between 6/10 (12) KV and 18/30 (36) KV.

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