ZILINSKIS · MV 15 kV
Undergrounding of the MV 15 kV line GPZ Toruń Podgórz – Włocławek 3 with the Brzoza 1, 2 and 3 branches
For ZILINSKIS Sp. z o.o. we replaced overhead sections of a 15 kV line with a cable line of 5,725 m route length in 3× XRUHAKXS 1×150 mm² cable. We installed 2 ZKSN junctions, completed ~600 m of directional drilling and pipe jacking, 6 sets of joints and 4 sets of connector terminations — all in under two months, for PLN 682,000 net.
| Client | ZILINSKIS Sp. z o.o. |
|---|---|
| Location | Toruń — GPZ Toruń Podgórz – Włocławek 3, odgałęzienia Brzoza 1–3 Kuyavian-Pomeranian Voivodeship |
| Voltage | SN-15 kV |
| BIGBUD's role | Construction subcontractor |
| Net value | PLN 682,000 net |
| Completion period | 30 Sep 2024 – 25 Nov 2024 |
The task
Undergrounding a line out of GPZ Toruń Podgórz
ZILINSKIS Sp. z o.o. of Toruń is a contractor working in the power sector, delivering projects for network operators. On this job BIGBUD worked as the construction subcontractor.
The contract was titled „Wykonanie robót budowlanych – Toruń, Toruń gmina miejska: Skablowanie linii SN-15kV GPZ Toruń Podgórz – Włocławek 3 wraz z odgałęzieniami Brzoza 1, Brzoza 2 i Brzoza 3, OBMBS/91/18485” — undergrounding of the 15 kV line from GPZ Toruń Podgórz to Włocławek 3 with its Brzoza 1–3 branches. The line leaves a GPZ — a primary substation where high voltage is transformed to medium voltage — and feeds a series of branches. Undergrounding it means replacing conductors on poles with cable laid in the ground.
Works ran from 30 September to 25 November 2024 — 57 calendar days for almost 6 km of route, including drilling and cable accessories.
How the works went
From setting out the route to connector terminations
The typical sequence of MV line undergrounding, mapped to the scope in the reference letter.
- 01
Route and obstacles
Setting out the 5,725 m route and identifying crossings with roads, watercourses and other utilities. Where an open trench is impossible or uneconomic, drilling is planned.
- 02
Drilling and jacking — ~600 m
Under roads and other obstacles, around 600 m of directional drilling and pipe jacking was carried out; protective ducts are installed in the bores and the cables pulled through.
- 03
Trenching and cable laying
Along the rest of the route, the 3× XRUHAKXS 1×150 mm² cables were laid in open trench — on bedding, with cover and warning tape, leaving slack at the junctions.
- 04
ZKSN Brzoza 5 and Brzoza 6
Two ZKSN medium-voltage junctions were installed, designated Brzoza 5 and Brzoza 6 in the letter. Junctions let the line be sectionalised and branched.
- 05
Joints — 6 sets
Cable lengths from successive drums were connected with 6 sets of 15 kV MV cable joints. A set typically covers all three phases of the line.
- 06
Connector terminations — 4 sets
Cable ends were connected in the junctions using 4 sets of connector terminations, followed by testing and handover of the documentation for acceptance.
Technology
Cable, junction, accessories — what the letter's items mean
A general explanation of the solutions used in MV line undergrounding.
3× XRUHAKXS 1×150 mm²
XRUHAKXS is a Polish-standard single-core MV cable with an aluminium conductor, XLPE (cross-linked polyethylene) insulation, a copper wire screen with longitudinal water-blocking and a reinforced polyethylene sheath. A three-phase line needs three such cables — hence “3×”. The 150 mm² refers to the conductor. More: MV cables: XRUHAKXS and NA2XS(F)2Y.
MV cable junction (ZKSN)
A ZKSN is a free-standing medium-voltage cable junction — an enclosure with switching equipment where cable lines are connected, branched and sectionalised. It lets the operator isolate part of the network without taking the whole line out, shortening interruptions during faults and works.
Why directional drilling
Horizontal directional drilling (HDD) installs a duct under a road, watercourse or tree line without digging up the surface or stopping traffic. The rig steers the drill head along a planned path, then reams the bore and pulls the duct in. More: How directional drilling works and our HDD service.
Joints and connector terminations
A joint connects two cable lengths, restoring insulation, screen and sheath — its quality decides the line's reliability for decades. A connector termination is a plug-in cable end that connects to the bushings of the switchgear in a junction or substation.
What this project shows
The full undergrounding scope under one roof
Undergrounding an MV line brings several specialities together: earthworks, drilling, cable laying, fitting accessories and installing junctions. In Toruń we delivered all of them under a single contract, so the client did not have to coordinate several firms on one route.
The pace came from organisation: drilling and open trenching can progress in parallel on different sections, and jointing and terminating start as soon as successive cable lengths are in the ground. Almost 6 km of route in 57 days is a result the client confirmed in its reference letter — noting that the works were completed on the agreed dates and without defects.
We bring the experience from this job to further undergrounding contracts, both for contractors working for network operators and directly for DSOs. See our overhead line undergrounding service and how we work.
- 5,725 m of MV cable route in 57 days
- drilling, cable, junctions and accessories in one scope
- a repeat contract from the same client — RS Maliniec in Konin
„The above-mentioned works carried out by BIGBUD […] were performed properly, in accordance with good construction practice, on the agreed dates and without defects.”
See also
Overhead line undergrounding
Undergrounding of MV and LV overhead lines: new cable line, HDD crossings, ZKSN junctions, switching and removal of the old line, poles included.
Learn moreHorizontal directional drilling
Horizontal directional drilling and pipe jacking under roads, railways and rivers — ducts for MV, LV and fibre cables. Own Tracto-Technik GRUNDODRILL rig.
Learn moreKonin — RS Maliniec 15 kV switching station
MV feeder cables for the RS Maliniec 15 kV switching station in Konin for ZILINSKIS: 5,410 m of 3×XRUHAKXS 1×240, ZKSN junction, ~350 m HDD. PLN 642,000 net.
Learn morePlanning to underground an MV line?
We can deliver the full scope — trenching, drilling, cable, junctions and accessories — or a selected part as a subcontractor.