An Electrical Substation is an essential module of an Electrical Generation-Transmission-Distribution arrangement, which converts voltage from high to low or vice-versa by using a step-down or step-up transformer depending upon the needs. Generally, before transmission, a substation increases the voltage by decreasing current using a step-up transformer and before distribution, a substation decreases the voltage by increasing the current using a step-down transformer. Between consumer and generating stations, there may be several substations to transform the voltage in several steps. An electrical utility or a large industrial or commercial customer can own a Substation and they can operate it by their electrical engineers & technicians. However, engineers generally supervise and operate substations from remote control stations using systems like SCADA.
Types of substation:
There are basically two types of substations, Transmission substations and distribution substations. In transmission substations, we step-up the voltage for transmission benefits. On the other hand, in distribution substations, we step-down the voltage for distribution reasons.
This type of substation is used before transmission. Transmission substations can either small or large, in a verity of range. Simple “switching station” may be an arrangement of a bus and some circuit breakers. The complex transmission substations can cover a huge area with several hectares of land with many circuit breakers, multiple voltage levels and a large number of protective devices and control units having relays, SCADA, CTs and PTs.
This type of substation is used before distributing electricity to consumers. Distribution voltages are typically medium voltage, generally ranging between 2.4 kV to 33 kV, which completely depends upon the size of the local area. Additionally, distribution substations play a vital role to isolate faults in either distribution or the transmission systems.
Main Equipment of an Electrical Substation:
Electrical Substations mainly have protective elements, switching elements, and Transformers. The main parts and detail list of elements are:
- Overhead lines
- Primary power lines – A
- Secondary power lines – B
4. Power Transformer
- Disconnector switch
- Circuit breaker [ to interrupt any overload current flow or short circuits]
7. CT (current transformer)
8. Lightning arrester as LPS
10. Control Unit
11. Security fenced enclosure
12. Grounding wire/ Earthing System
However, some other elements like voltage regulators, capacitor bank and reactors can be also be used in a substation.