MV/LV transformer substations
Transformer substations, ZKSN junctions and switching stations
We install MV/LV transformer substations and cable junctions, bring in MV and LV cables, fit terminations and remove retired pole-mounted substations. For ENEA Operator we built 3 new MV/LV substations to replace pole-mounted units.
What the service covers
Where medium voltage becomes low voltage
An MV/LV transformer substation steps the medium-voltage network (usually 15 or 20 kV) down to the 0.4 kV that supplies customers. It consists of MV switchgear, a transformer, LV switchgear and an enclosure — ground-mounted (kiosk), indoor or pole-mounted. An MV cable junction (ZKSN) serves as a branch or open point in the cable network, while LV pillars distribute power to customers.
New substations are needed when the network is extended, when new customers and renewable sources are connected, and when lines are undergrounded and the pole-mounted substations on the retired line must be replaced. We explain how a substation is put together in Inside an MV/LV substation.
Our scope covers the civil and electrical installation work: preparing the base and setting the substation or junction, laying and bringing in the cables, fitting terminations and making MV and LV connections, earthing, testing, and removing substations taken out of service.
- Installation of MV/LV transformer substations and ZKSN junctions
- MV and LV cable entry and connection, indoor and connector terminations
- Removal of pole-mounted transformer substations
Scope of works
What we do on substations and junctions
Site preparation
Excavation, bedding and base preparation for kiosk substations and junctions, following the manufacturer's documentation and the design.
Transport and setting
Unloading and setting junctions and substation components with a loader crane or a mobile crane sized for the unit.
Earthing
Installing the earthing system for substations and junctions and measuring earth resistance.
Supply cables
MV cable lines feeding the substation or switching station and LV outgoing circuits to customers. More: cable lines.
Terminations and connections
Indoor, connector and outdoor terminations, MV and LV connections, cable labelling.
Replacing pole-mounted units
Dismantling pole-mounted transformer substations once customers have been switched to the new substation.
How the works run
Stages of building a substation or junction
Design and location check
We check the substation location, delivery access, ground conditions and the routes of the supply cables and LV circuits.
Scope of works
- site visit
- crane access check
- materials schedule
Result
- delivery and installation plan
Arrangements
We agree equipment delivery, outage and connection dates with the operator, and working arrangements with the landowner.
Scope of works
- delivery dates
- outage programme
- notifications
Result
- connection programme
Earthworks and earthing
We prepare the excavation and base for the substation or junction, install the earthing system and dig for the cables.
Scope of works
- excavation
- bedding and compaction
- earth electrode
Result
- base ready for setting
Setting and cabling
We set the substation or junction, lay the MV and LV cables and bring them into the unit.
Scope of works
- unloading and setting
- cable laying
- sealing cable entries
Result
- unit with cables brought in
Terminations and connections
We fit terminations, connect the MV and LV cables and, on the agreed date, energise the unit and switch customers over.
Scope of works
- fitting terminations
- MV and LV connections
- connection to the network
Result
- substation in service
Testing, dismantling and documentation
We carry out measurements, remove the replaced pole-mounted substations and hand over the as-built documentation with the geodetic survey.
Scope of works
- earthing and insulation measurements
- removing pole-mounted units
- as-built survey
Result
- acceptance reports
Technical solutions
Typical installations in an MV/LV network
Indicative only. The type of substation, transformer and switchgear is set by the design and the operator's standard.
| Installation | Function | Typical components |
|---|---|---|
| Kiosk (ground-mounted) MV/LV substation | Supplying customers from a cable or mixed network | MV switchgear, transformer, LV switchgear, concrete or composite enclosure |
| Pole-mounted MV/LV substation | Supplying customers from an overhead line | Transformer on a pole structure, switch-disconnector, surge arresters, LV board |
| MV cable junction (ZKSN) | Branch or open point for MV cable lines | Line panels with connector terminations, free-standing enclosure |
| MV switching station (RS) | MV network node distributing supply to several lines | Multi-panel MV switchgear, indoor terminations |
| LV cable pillars | Power distribution and customer supplies | Fuse bases, terminals, cabinet enclosure |
A case in point
Three new substations in place of pole-mounted units
On the contract for ENEA Operator in Stara Jabłonna, Nowa Jabłonna and Zimna Brzeźnica (Niegosławice municipality) we were consortium leader. The works ran from 16 October 2025 to 28 May 2026, with the programme spanning the winter months.
The scope combined several services: installing and building three sets of new MV/LV transformer substations, an MV cable line of 1×150/25 mm² with a length of 3 × 5,715 m, LV cable lines (4×150 mm² — 766 m and 4×25 mm² — 6 m) and two ZK1x-1P cable junctions, followed by the removal of three pole-mounted transformer substations and 8.266 km of MV overhead line. The contract value was PLN 2,405,200 net.
In Konin, as a subcontractor to ZILINSKIS, we built the MV cable lines feeding the new 15 kV RS Maliniec switching station (6 sections totalling 2,890 m plus a 2,520 m line), installed a 3-way ZKSN cable junction on ul. Rybacka and fitted joints and terminations — indoor, outdoor and connector. Details: ENEA Operator and RS Maliniec.
Projects
Substations, junctions and switching stations in our work
For ENEA Operator — 3 sets of new MV/LV transformer substations, 2 ZK1x-1P cable junctions and the removal of 3 pole-mounted substations. In Konin — 15 kV supply lines for the RS Maliniec switching station, a 3-way ZKSN junction and 18 sets of MV joints and terminations.
ENEA Operator — MV 20 kV network, Niegosławice
Lubuskie Voivodeship
Konin — RS Maliniec 15 kV switching station
Greater Poland Voivodeship
„The works were performed with due care, in accordance with the terms of the contract and the applicable technical requirements.”
Photos
From our sites
Questions
Transformer substations — frequently asked questions
Do you also supply the substations and transformers?
The equipment is most often supplied by the client or the operator. On request we arrange deliveries through our equipment supply service, to the specification in the design.
What is a ZKSN junction?
It is a medium-voltage cable junction — a free-standing enclosure with panels where MV cable lines are connected using connector terminations. It is used to branch the network or as an open point. We have installed ZKSN junctions in Toruń (Brzoza 5 and Brzoza 6) and in Konin (ul. Rybacka), among others.
Do you remove old pole-mounted substations?
Yes. In the Niegosławice municipality, once the new substations were in service, we removed 3 pole-mounted transformer substations together with the overhead lines.
Do you build substations for solar and wind farms?
We deliver cable infrastructure and installation work on substations and junctions for renewable plants. The scope for a particular farm is agreed individually — see solar farms.
See also
Related topics
Inside an MV/LV substation
Inside an MV/LV transformer substation: pole-mounted and packaged types, MV switchgear, the transformer, LV switchboard, earthing and how a substation is built.
Learn moreMV and LV cable lines
Construction, rebuilding and repair of MV 6–30 kV and LV 0.4 kV cable lines: trenching, drilling, cable laying, joints, terminations, testing and handover.
Learn moreEquipment supply
Equipment procurement for MV and LV networks: XRUHAKXS and NA2XS(F)2Y cables, joints, terminations, ZK/ZKSN junctions, substations and ducts to DSO specs.
Learn moreA substation or junction to install?
Send us the design — we will quote for installation, supply cables and connections.