In this blog, I have primarily focused on explaining what an electrical substation is and its classification based on the usage of dielectric mediums.
Electrical substation
Certainly! An electrical substation is a fascinating place where the electricity we use every day is managed and distributed. It acts as a "magical hub" because it performs an important task that helps bring electricity to our homes, schools, and other places.
One of the primary functions of an electrical substation is to adjust the voltage level of the electricity. Voltage is like the power or force of electricity. Sometimes, the electricity generated at power plants has a very high voltage that is not suitable for our homes and buildings. In such cases, the substation steps down or reduces the voltage to a safe and usable level.
On the other hand, when electricity needs to travel long distances, it is more efficient to transmit it at higher voltages. So, the substation can also step up or increase the voltage when needed, to enable electricity to travel over long power lines without losing too much energy.
By adjusting the voltage levels, the electrical substation ensures that the electricity is just right for different purposes and locations. Once the voltage is at the desired level, the substation sends the electricity through power lines and cables to our homes and other places where we use it.
So, in a way, an electrical substation acts as a magical hub that transforms and controls the electricity, making it safe and usable for our everyday needs. Without substations, it would be challenging to distribute electricity efficiently and bring power to the various devices and appliances we rely on
Difference between Switchyard and Switchgear
Switchyard ; A switchyard is an outdoor area or space where various electrical equipment, such as transformers, circuit breakers, Contactors and electrical switches are located. It acts as a hub or central point for the transmission and distribution of electricity. Think of it as a kind of "electrical traffic control center" where the electricity is managed and directed to different places.
Switchgear: Switchgear refers to the equipment or devices used to control, protect, and regulate the flow of electricity within a switchyard or electrical system. It includes things like switches, circuit breakers, and other components that ensure the safe and reliable operation of the electrical network. Switchgear is like the "electrical control panel" that allows engineers or operators to turn the electricity on or off and protect the electrical system from any faults or damage.
Classification of a substation based on Dielectric medium
- Conventional air-insulated substation.
- Gas-insulated substation.
- Hybrid substation.
Conventional Air-insulated substation.
A conventional air-insulated substation uses natural air as the dielectric medium. The breakdown voltage of atmospheric air is considered to be around 3 kV/mm. However, if the atmospheric air is polluted, this breakdown voltage may decrease from its actual level. The air-insulated substation (AIS) is capable of operating at voltage levels of 66 kV and above. Beyond this voltage rating, substations require more space.
Due to its outdoor installation, an AIS does not require any other dielectric medium apart from air.
Dielectric medium* - a medium that quenches or extinguishes an arc.
Structure (AIS).
In a conventional air-insulated substation, all electrical components, including busbars, circuit breakers, and isolators, are installed in an outdoor setting and are visible. The design of an air-insulated substation enables convenient expansion if space is not a constraint. Insulators such as post insulators or strain insulators provide support for the busbar. The substation employs galvanized steel structures, also known as gantry structures, to support the electrical equipment, insulators, as well as the incoming and outgoing lines.
The size of electrical equipment in a substation is directly proportional to the rated voltage. Since substations handle high voltages, the equipment size is considerably large, and the clearance between two live conductors (phase to phase) and between the ground and live conductor (phase to ground) also increases.
To prevent step-potential and touch potential hazards during a short circuit or fault conditions, the substation floor is typically filled with stones and gravel.
ADVANTAGE:-
- The air-insulated substation is best suited for the outdoor and the initial cost is very low.
- It can operate even at the rated voltage of 66KV and above.
- Easy to Maintenance.
- This type of substation requires more space it occupies a large area.
- This substation is more compact but complex.
- This substation is situated in an outdoor environment so it requires more protection from a natural disaster.
- This is compact but complex.
- If the insulation property of air gets pollutant then it becomes inefficient.
- Regular maintenance is required.
Gas-insulated substation.
Structure (GIS).
A gas-insulated substation utilizes SF6 gas (sulfur hexafluoride gas) as its dielectric medium. The breakdown voltage of SF6 gas is three times higher than that of air. These substations were developed in the 1970s and have gained significant popularity in countries such as Saudi Arabia, the USA, Europe, Japan, and more. GIS installations have been implemented in India since 1989. These substations are highly efficient and well-suited for high-density urban areas where space availability is limited. They are preferred not only for indoor installations but also for outdoor installations.
SF6 gas provides excellent dielectric strength when used at moderate pressure for insulation between phases and between the conductors and the ground. It is a non-toxic, man-made gas with a long lifetime ranging from 800 to 3200 years. The gas's insulating property is non-flammable, providing insulation between live conductors and the ground.
- This substation requires only 15% of the floor area of the AIS substation.
- Highly reliable compare to the AIS substation.
- The life span of gas is more.
- No degradation via weathering.
- The cost of a gas-insulated substation is higher compared to an air-insulated substation (AIS).
- In the event of an internal fault, extensive damage can occur to the electrical equipment, and the time required for rectification will be longer.
- A pressure monitor for SF6 gas is installed in every compartment.
- A large quantity of SF6 gas is more harmful to the environment as it can contribute to ozone depletion and global warming.
Hybrid substation.
The hybrid substation is essentially a combination of an air-insulated substation (AIS) and a gas-insulated substation (GIS), utilizing both air and Sf6 gas. as insulation mediums.
Substation hybridization* is the concept of mixing two substations into a new hybrid substation.
Structure (HIS).
The hybrid substation is a combination of indoor and outdoor components. In a hybrid substation, certain bays are equipped with an air-insulated medium, while the remaining bays are enclosed with SF6 gas-insulated medium. The rated voltage level of a hybrid substation can range from 145 kV to 550 kV.
- Hybrid substation combines the advantages of both air-insulated substation and gas-insulated substation.
- Low maintenance.
- Cost reduction.
Classification of a substation based on the rated voltage
We can classify the substation based on its rated voltage level.
- UHV A.C and EHV A.C Substation (Voltage rating is 400 Kv to 765 Kv).
- High voltage A.C Substation (Voltage rating is 66 Kv to 220 Kv).
- Distribution substation (Voltage rating is 3.3 kV to 33 Kv).
- Low voltage substation (voltage rating is 600 volts to 400 volts).
thanks for sharing a knowledge "Electrical isolator "
ReplyDeletenice post! What wire is rated for 600V can you post more about power cables wholesale thanks!
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