The substation is the medium of transferring the power from generating unit to the consumer end. It consists different types of equipment like transformer, generator, power cable which helps in the power transmission. The generation, transmission and distribution are the main work of the substation.
The substation which generates the power is known as the generating substation. Similarly, the transmission substation transmits the power, and the distributing substations distribute the power to the load. The subcategories of the electrical substations are explained below.
Classifications of Substations
The substations may be classified in numerous ways, such as by nature of duties, service rendered operating voltage, importance, and design.
Classification of Substations by Nature of Duties
The classification of the substation by nature of functions is explained below in details.
Step-up or Primary Substations – Such types of substations generate low voltage like 3.3, 6.6, 11, or 33kV. This voltage is stepped up by the help of a step-up transformer for transmitting the power over large distances. It is located near the generating substation
Primary Grid Substations – This substation lowered the value of primary stepped up voltages. The output of the primary grid substation acts as the input of the secondary substations. The secondary substation is used for stepping down the input voltage to more lowered for further transmission.
Step-down or Distribution Substations – This substation is placed near the load centre where the primary distribution is stepped down for sub-transmission. The secondary distribution transformer feeds the consumer through the service line
Classification of Substations by Service Rendered
Transformer substations – In such type of substation transformers are installed for transforming the power from one voltage level to another level as per need.
Switching Substations – The substations use for switching the power line without disturbing the voltage is known as the switching substations. This type of substations is placed between the transmission line.
Converting Substations – In such types of substations, AC power converting into DC power or vice versa or it can convert high frequency to lower frequency or vice versa.
Classification of Substations by Operating Voltage
The substations, according to operating voltage, may be categorised as
High Voltage Substations (HV Substations) – Involving voltages between 11 KV and 66 KV.
Extra High Voltage Substations – Involving voltages between 132 kV and 400 KV.
Ultra High Voltage – Operating voltage above 400 KV.
Classifications of Substation by Importance
Grid Substations – This substation is used for transferring the bulk power from one point to another. If any fault occurs on the substation, then the continuity of whole of the supply is affected by it.
Town Substations – These substations step down the voltage at 33/11 kV for more distribution in the towns. If there is any fault occurs in this substation, then the supply of the whole town is blocked.
Classification of Substations by Design
Indoor Type Substations – In such type of substations, the apparatus is installed within the substation building. Such type of substations is usually for the voltage up to 11 KV but can be raised for the 33 KV or 66 KV when the surrounding air is polluted by dust, fumes or gasses, etc.
Outdoor Substations – These substations are further subdivided into two categories
Pole Mounted Substations – Such Substations are erected for distributions of power in the localities. Single stout pole or H-pole and 4-pole structures with relevant platforms are operating for transformers of capacity up to 25 KVA, 125 KVA, and above 125KVA.
Foundation Mounted Substations – Such types of substations are used for mounting the transformers having capacity 33,000 volts or above.