This blog is part of a 2-part series on the components of our electrical grid: the lines and cables, which transport electricity, and the substations, which process the power. So, what is inside a substation?
The substation
The substation plays a key role in the electric grid by serving as a point that brings together power lines and controls several key functions. It maintains voltage, frequency and current, and contains protection systems in case of a failure or issue.
They can be located outside or inside, depending on their proximity to urban centres. When my Power Grid Technology class from KTH Royal Institute of Technology visited Skanstull, one of the main substations that feeds Stockholm, we were able to see all the components of a substation and how they work together to reliably and safely deliver power.
The components
First and foremost, connecting all the different components are bus bars, which compose the bulk of the metal tubes you see when looking at a substation. They carry the current from one component to another.
One of the key components of most substations is the transformer, which converts between different voltages. In fact, often there are several transformers at a single substation. If the substation is located at a connection point between two adjacent power systems, it may be a “phase-shifting transformer”, which synchronises the electrical phase between the two power systems.
Some substations, known as a “switchyard” or “switching substation”, do not have a transformer. Instead, they operate solely at one voltage level, with the primary purpose to switch the current flow between different lines or circuits. Switching events can be planned – as in the case of maintenance work or optimising system performance, or unplanned, in case of failures or emergencies.
Another important component is the circuit breaker. As its name suggests, it breaks, or interrupts, any short circuits or overload currents that may occur in the network to protect the remaining components of the system. It receives a signal from the relay, which is a fault detecting device.
In fact, there are many protective components inside substations, as electricity naturally carries high safety risks. These also include insulators (which insulate bus bars), isolators (which is a kind of disconnection switch used under no-load conditions), and lightning arrestors (which protect especially the most valuable equipment in the case of thunderstorms).
Substations also contain a significant amount of monitoring and control equipment. This includes the current transformer, which measures current. They also often provide voltage regulation and/or power factor correction, via devices such as capacitor banks, reactors, or static VAR compensators.
Studying sustainable electrical power systems
Interested in substation components and how they work together to deliver power reliably and safely to end-users? Power systems are a major focus of the EIT InnoEnergy Master’s in Smart Electrical Networks and Systems, where I learned all this information and how it relates to the energy transition.
For one, whereas power flow was traditionally uni-directional, nowadays, more and more homeowners with solar photovoltaic panels are sending out excess electricity onto the grid. This bi-directional power flow is presenting huge challenges, especially for distribution system operators, in terms of power system control. Talented engineers are needed to help solve these issues and build the smart grid of the future!
Fascinated by the world of electricity? I was too, and so I joined the Master’s in Smart Electrical Networks and Systems. Now I know fascinating facts and answers to age-old questions, like how birds can sit on power lines. Are you also interested? Apply today!
by Emilia Chojkiewicz