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Medium Voltage Cable Installation
MV cable installation: XLPE pulling, bending radius control, joints and terminations, bonding and certification tests for feeder routes.
Medium voltage cable installation is the laying, termination and verification of XLPE (cross-linked polyethylene) insulated cable routes from 3.6/6 kV up to 36 kV between substations and cells-panels-consumer facilities. The MV cable is the artery of the plant: dozens of metres running continuously underground or in galleries, and one termination defect locks the whole route. Installation is therefore an accessory-craft discipline built on pulling-force limits, bending radius and clean-room-like cleanliness. Our service runs end-to-end turnkey: survey and route plan, paying-off, pulling, joint-head making through certification testing.
Laying Engineering
- Route and bedding: Below-grade layers of bed-protection-brick-warning tape, the bending radius at every bend (typically 12-20 times cable diameter), support span and clamp type in trays-galleries including thermal expansion length are controlled.
- Pull control: Exceeding the permitted pulling force (kN, calculated per section-stress) elongates the conductor and moves the joint; cables are pulled with dynamometer-roller-lubricant and the route is wound accordingly.
- Phase-earth arrangement: In single-core MV cables the flat-trefoil choice, the metallic screen earthing style (single-end, double-end, transverse bonding) hold induced screen voltage within limits; armour-bonding continuity (earthing) is mandatory.
- Fire and compartment: Sealing at wall-gallery passages (fire stops), separation from high current in the shared infrastructure and slope-distance planning.
Accessory Craft: Joints and Terminations
An MV cable system works on continuous electric-field stress control across conductor-semicon-XLPE-screen-armour layers; joints and terminations rebuild those layers. Strip depths, removal of semiconductive residues, heat-shrink temperature-time protocols and atmospheric-water barrier seals are the critical control points of head work. This craft is done by manufacturer-trained certified personnel in full obedience to the procedure — the secret of termination quality is cleanliness and discipline, not tools. Products are type-tested per TS EN ISO 11444 (accessories 11-36 kV) and the HD 629/630 set; details are handled in our MV termination installation page.
Testing, Certification and Legal Basis
After installation the route is accepted with insulation resistance, phase-phase-phase-earth integrity and screen-earthing continuity, then the on-site cable test: per HD 620.1.S1/IEC 60840, 15 minutes at 2U0 or stepped VLF oscillation with PD monitoring for dielectric verification. Protocols are archived per route segment and enter the commissioning file. Work runs under Law No. 6331, the High Current and Internal Electrical Installations Regulations, distributor specifications and cable-accessory standards; excavation-passage works tie to municipal infrastructure permits. A correctly laid MV cable is invisible and fault-free for thirty years. For route survey and quotation see the contact page; this service sits under MV Contracting.
FAQ on Medium Voltage Cable Installation
The MV cable is the artery of the plant: it must run for decades underground or in galleries and one craft error locks the whole route. The pulling force limit must not be exceeded (the conductor stretches, the joint moves), the bending radius preserved (typically 12-20 times diameter), and thermal cycling-mechanical damage risk managed in the route plan. Accessories are made by manufacturer-certified staff; details sit in our termination installation service.
In the below-grade section the bed-protection-brick-warning tape layers; in gallery-tray the support span, clamp type and thermal expansion length; for single-core cables the trefoil-flat choice and the metallic screen earthing style (single end, double end, transverse bonding) that holds induced screen voltage within limits. Armour-bonding continuity (earthing) is mandatory; fire compartment passages close with sealed sleeves and strong current separation (cabling) is planned.
The route is accepted after insulation resistance, phase-earth integrity and screen-earthing continuity with the HD 620.1.S1/IEC 60840 verification: 15 minutes at 2U0 stepped DC, or VLF oscillation plus partial discharge monitoring for dielectric proof. The protocol archives per segment and enters the commissioning file; the first values are the baseline of later periodic diagnostics (tan delta-VLF-PD).
On lines with a 30 plus year design life the load cycle feeds thermal ageing and switching stresses feed water treeing. Periodic diagnostics — tan delta, VLF with PD monitoring, thermal mapping — opens the early warning window; excavation-vibration-rodent mechanical damage risk falls with warning tape-clamp audit. Asset based route-joint-head records cut fault localisation from hours to minutes.