What is an Electrical Substation?

Electrical substations are important components of the electrical grid. Essentially, they are the connectors of the power delivery system. Before a consumer can utilize energy, power must travel from the power plant through a complex network of transmission and distribution lines. Transmission lines typically run high voltages, while distribution lines are engineered to carry lower voltages. Substations designed with transformers change voltage levels between high transmission lines to lower distribution lines or connect transmission lines with different voltages.

In addition to electrical substation transformers, substations are generally equipped with switching, protection and control equipment. Large transformers house circuit breakers that are used to mitigate short circuits and overload currents. Capacitors, voltage regulators and reactors are also frequently included in the substation.

Electrical Substation Safety
From a safety standpoint, the grounding system is the most important power substation design feature. A substation design engineer must calculate the total ground potential rise during a short circuit in the transmission system. During a fault, the electrical current is discharged into the ground. Since the earth is not a conductor, it is typically safe to walk on the ground surrounding a substation. However, conductive materials such as metal fencing pose a significant safety threat. Metal objects can become electrified and can be hazardous to the touch. “Touch and step potentials” as they are commonly called, must be calculated during substation design engineering. Hazards must be identified and appropriately grounded to protect both utility workers and the public.

Types of Substations
Substations are classified in a variety of ways. They can be categorized by their voltage, function, and type of connection insulation. To provide an overview of the most common types of electrical substations. We will classify the different types of substations based on their primary function.

Transmission Substations
A transmission substation connects two or more transmission lines. The transmission lines will all have the same voltage. High-voltage switches will enable lines to be connected or isolated. A more complex design may have transformers that convert two different transmission voltages. The largest and most sophisticated transmission substations can cover several acres of land and connect multiple voltages with lots of different control and protection equipment. 

Distribution Substations
A distribution substation transfers energy from the transmission system to distribution lines. Unless customers use large amounts of power, it does not make economical sense to connect individual customers to transmission networks. Distribution substations reduce the voltage from transmission lines so energy can flow through distribution lines that connect to individual customers. Like transmission substations, distribution substations can be simple or complex. Most distribution substations have a single switch, transformer, and minimal facilities on the low-voltage side.  However, urban areas may require more complicated distribution substations, with both high-voltage switching and switching and backup systems on the low-voltage side. 

Collector Substations
Wind farms, hydroelectric power plants, and other renewable energy sources often require collector substations. These electrical substations to step up the collected voltage to transmission rates. 

Switching Substations
A switching station operates at a single voltage and does not have any transformers. They can be used as collector and distribution stations. However, their primary purpose is to back up lines or create redundancies in case of failure. They do this by connecting and disconnecting transmission lines or other components of the system. Switching substations are useful for planned and unplanned outages. They allow new line construction, transformer substation maintenance, and system repair to be performed without interruption of service to customers.   

Energizing North America

Matrix NAC is considered an industry leader in substations, power, and industrial work. Contact us for your next power delivery project.