Electrical substations are facilities that are responsible for carrying out transformations of voltage, frequency, number of phases or connections of two or more circuits. Generally, they are located near power plants, on the periphery of consumption areas or outside and inside buildings.

An electrical substation, in other words, is a facility that is part of an electrical power system. Its main objective is to modify and establish the voltage levels of an electrical infrastructure, to facilitate the transmission, distribution and final use of electrical energy.

In other words, for energy to reach your home or business, it must first pass through a substation that will level its power and transform it, so that you can use it without any inconvenience.

Electrical substations intervene in the generation, transformation, transmission and distribution of electrical energy. An electrical substation is made up of devices capable of modifying the parameters of electrical power (voltage, current, frequency, etc.) and are a means of interconnection and dispatch between the different lines of an electrical system.

Types of Electrical Substations

Electrical substations can be classified into two groups:

  • Transformation substations. They transform the voltage of electrical energy through one or more transformers. It can be step-up or step-down.
  • Switching substations. They connect two or more circuits and carry out their maneuvers. In this type of substations, the voltage is not transformed.

The main element of electrical substations is the transformer that is responsible for modifying the voltage of electrical energy by increasing intensity and constant power.

Main elements of electrical substations

The main elements of a substation are:

  • It is a static electrical machine that transfers electrical energy from one circuit to another while keeping the frequency constant, operates under the principle of electromagnetic induction, and has electrical circuits that are magnetically linked and electrically isolated.
  • Power switch. It interrupts and restores the continuity of an electrical circuit. The interruption must be made with load or short circuit current.
  • It is an oil switch with its three contacts inside the same tank and that operates in low switching capacities. Reclosers are built to operate with three reclosing and four opening operations with an interval in between; in the last opening the closing must be manual, since it indicates that the fault is permanent.
  • Fusible blades. They are elements of connection and disconnection of electrical circuits. They have two functions: one as a disconnect blade, for which it connects and disconnects, and another as a protection element. The protection element is constituted by the fuse device that is inside the connection and disconnection cartridge.
  • Disconnect blades and test blades. They serve to physically disconnect an electrical circuit. They are usually operated without load, but with some accessories they can be operated with load up to certain limits.
  • Lightning arresters. It is permanently connected to the system; it discharges the current to ground when an overvoltage of a certain magnitude occurs. Its operation is based on the formation of an electric arc between two spark gaps when the value for which it is calibrated or dimensioned is reached.
  • instrument transformers. There are two types: current transformers (CT), whose main function is to change the value of the current in its primary to another in the secondary; and potential transformers (PT), whose main function is to transform voltage values ​​without taking current into account. These values ​​serve as real-time readings for measurement, control, or protection instruments that require current or voltage signals.
  • Derivative Boxes. They are the connection terminals per phase.

Benefits of Electrical Substations

Greater security of supply

In general, the power supply of the substations comes from high-voltage lines that, because they are protected, make the probability of failure less. Therefore, there is better voltage regulation.

Rational use of energy

By reducing voltage drops, the use of heavy gauge conductors also decreases, so it is possible to have distribution voltages of 440 V, 2300 V, 4160 V, etc., with less loss.


The cost of high voltage power supply is lower than that of low voltage. In addition, the installation of substations in large consumption centers saves materials such as cables and ducts.

Before designing a substation, it is necessary to request from the utility company data such as available voltage level, voltage level variation, supply delivery point and line route, three-phase short-circuit current and single-phase at the point of supply and rates.

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