SUBSTATION

 WHAT IS SUBSTATION? TYPE OF SUBSTATIONS?

EQUIPMENT USED IN SUBSTATION?

Substation: It is a place where lot of electric equipment (like transformer, circuit breaker, Current transformer, voltage transformer etc) install and operate for control of transmission and distribution of electric power. 

OR

It is a place where mainly voltage transformation take place with the help of electric equipment (transformer).

Main functions of substation is given below:

1. To close and open the power lines. 
2. To raise or lower the voltage,this operation is known as voltage transformation operation.
3. To convert a.c. into d.c. or vice versa.
4. To change the frequency of supply,this operation is known as frequency operating operation.
5. To improve the power factor at the end of the line by the use of capacitor bank or synchronous condenser,this operation is known as power factor correction operation.

TYPES OF SUBSTATIONS:

According to design substation has two types.

1. Outdoor substation
2. Indoor substation

1.OUTDOOR SUBSTATION: In this type of substation the electric equipment are installed in open,so this type of substation is called outdoor substation.This type of substation is mainly used for voltage up to 66 kV and above.It is used for receive and transmit large electric energy,so high rating of equipment used.So, such type of electrical substations require a large site and generally installed outside the city.

Main parts of outdoor substation:

1.Control room: In this type of substation a small building is required (as compared to indoor substation) for control room.It is a place from all the electric equipment can be control and operate.

The given below image show the building of control room and equipment installed in control room:

Building of control room

Control Room

The given below equipment install in control room:

a) Power transformer control panel: By the operation of this panel we can switch on and off the power transformer.

b) Circuit Breaker: By the operation of CB we can switch on and off the power lines (outgoing feeders).

c) Tap changer panel: By the help of tap changer panel we can change the secondary voltage of transformer.

d) Miscellaneous equipment: Battery,DC distribution panel,AC distribution panel,Battery charging panel etc is also installed in substation building.

2.YARD: It is the place where all the equipment is installed and operate in open.

The given below image show the yard of substation and the equipment installed in yard:

Substation yard

The given below equipment is installed in substation yard:

a) Isolator cum earth switch: It is a switch that can connect and break the main circuit (power line) from substation.It is always operate at no load.A earth switch also connect to it.With the help of this earth switch be can earth the main circuit.

b) Potential transformer: It is used for metering purpose.

c) Supporting isolator: This isolator is used for the support of  main circuit.

d) Breaker panel (Primary side): This is used for switch on and off main circuit.This is mainly operate by control panel that is situated in control room.

e) Current transformer: This is used for metering and protection purpose.

f) Lighting Arrestor: This is used to protect the other equipment from lighting.

g) Power transformer: It is a device that transfer power by the transformation of voltage (primary side to secondary side).

(For more information see the transformer topic in this site).

h) Neutral current transformer (NCT): It is a device used for earthing of neutral of power transformer ( transformer which have star winding).

The advantages and disadvantages of outdoor substation is given below:

1.Advantages:

a) Small building is required.

b) The fault location is easier.

c) In future the extension of installation is easier.

d) The construction work required is less.

e) Maintenance is easy.The work of maintenance can be carried out without making more of substation dead.

2.Disadvantages:

a) More space is required for the substation.

b) The dirt and dust deposits upon the outdoor substation equipment.

c) More maintenance is required.

d) The effect of temperature on equipment due to change in weather reduces the life of equipment.

2.INDOOR SUBSTATION: In these type of substation all the electrical equipment is installed in the building of substation.It is generally used up to 66 KV.It is mainly used where the surrounding atmosphere is contaminated with impurities and metal corroding gases,conductive dust etc.

In this type of substation all the electric equipment used same as outdoor substation but it is install in a panel.The panel is divided in different chamber and all the electrical equipment install in different chamber and it is insulated by sulfur hexa-fluoride (SF6) gas.

The advantages and disadvantages of outdoor substation is given below:

1.Advantages:

a) If a fault occurs on any section of the bus bar,that section can be isolated without affecting the supply from other section.

b) Easy operation.

c) Less space required.

2.Disadvantages:

a) Fault location is difficult.

b) Risk of fire is more.

c) Future extension is not easy.

d) Capital cost is high.

e) Time required for completion is more.

→Thus final conclusion is that outdoor substation is suitable for transmit and receive large electric power above 66 KV and indoor substation is used for transmit and receive small power up to 66 KV in urban area.