Transformer station — network's pivot point

If the electrical grid is a staircase of voltage levels, the transformer station is the very step. It is here that voltage is raised or lowered so current can move safely and efficiently to the next link in the system. For a supply operator, the transformer station is one of the most central workplaces — both during the education and later in the job.

§What happens inside a transformer?

A transformer basically consists of two coils wound around a common iron core. When current runs through one coil, a magnetic field is created which induces a new voltage in the other coil. The ratio between the number of turns in the two coils determines whether the voltage is stepped up or stepped down — it is the principle that makes it possible to transform current between the different levels in the network.

§The components in a transformer station

• 01The transformer itself that changes the voltage level
• 02Coupling system with switches that can connect and disconnect the individual fields
• 03Relays and fuses that protect the system and cut off during faults
• 04Grounding system and equalization connections are established.
• 05The target audience

§Hovedforløb 1: 10/0,4 og 20/0,4 kV

In the first main course of the education, you learn to build transformer stations at the level 10/0.4 and 20/0.4 kV — that is, the local stations that step down the current from the distribution network's medium voltage to the 400/230 volts that consumers use. Here you also work with cable work at 10-20 kV, system control, connecting a generator to the transformer and basic troubleshooting.

§Main course 2: up to 60 kV

In the second main course you move up a level and work with higher voltages — around 60 kV — which bind the local distribution networks together on a regional level. At the same time the curriculum is expanded with fibre, energy systems and understanding of how distribution network operators function as DSOs, so you get a broader picture of how the whole system fits together before you take your journeyman exam.

§Insulation and cooling – the oil's dual function

In many transformers, oil plays a central role. The oil insulates the current-carrying parts from each other and from the transformer's iron core, while at the same time transporting heat away from the coils when the transformer works under load. Therefore, checking oil level and any leaks is a fixed point in maintenance — if the level drops or a leak is discovered, it may be a sign of a fault that should be investigated before it develops.

It is precisely because the transformer station is so central to operations that safety rules weigh heavily when working in and around it. Work inside the station requires that you are either competent or properly instructed for the task and that the system is treated according to the same principles of disconnection protection against reconnection and control of de-energisation as apply to the rest of the electrical network.

§Different sizes same basic principle

Not all transformer stations look the same. Some are small, compact stations that supply a small residential area or a single street, while others are larger facilities with multiple bays that tie significant parts of a local network together. Regardless of size, the basic principle is the same: one or more transformers change the voltage level, while switching systems, relays and measuring equipment ensure that this happens safely and under control.

As a utility operator you will in practice encounter stations of many different sizes and ages — from newer remotely read systems to older stations that have been gradually upgraded over the years. The broad experience of both building new stations and maintaining older ones is a central part of what makes the trade versatile.

“Transformer station is place where theory about coils and magnetic fields becomes something you can stand beside hear and inspect”