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POSITION OF EQUIPMENT IN SUB-STATION

A-   Primary Power Lines (1)

B-   Secondary Power Lines (12)

2-   Ground Wire

3-   Over Head Line

4-   Potential Transformer(Voltage Transformer)

5-   Disconnecting Switch (Isolator)

6-   C.B.

7-   Current Transformer

8-   Lighting Arrester

9-   Main Transformer

10- Control Building

11- Security Fence

• A substation is a part of an electrical generation, transmission and distribution system.

• Substation transform voltage from high to low, or the reverse or perform any of other several important functions.

• Substation may be owned and operated by an electrical utility or may be owned by a large industrial or commercial customer.
• Generally substations are unattended, relaying on SCADA for remote supervision and control.

Power Transformer or Main Transformer

• This is the most important equipment of any substation around which all other equipments are arranged to protect this transformer from any abnormal system condition.

• Power transformer is used to increase voltage or current level of system without changing power level and frequency of system.

Circuit Breaker (C.B.)

• Circuit Breaker is used to control (break) circuit if any fault in any part of the substation system.

• Main function of Circuit Breaker is to open under faulty condition to clear the fault (This is done by C.B. with the help of relay) as well as under healthy condition for maintenance purpose.

• Types of Circuit Breaker

1. Oil Circuit Breaker
2. Air Break Circuit Breaker
3. Air Blast Circuit Breaker
4. SF6 Circuit Breaker
5. Vacuum Circuit Breaker

Instrumental Transformer

• Two type of instrumental transformers :

1. Potential Transformer
2. Current Transformer

Current Transformer

• Current transformers are basically used to take the reading of the currents entering the substation. This current transformer  steps down the current from 800 amp. to 1 amp.
• The main use of this transformer is for Distance Protect, Back up protection and measurement.

Potential Transformer 

• The main use of this transformer is to measure the voltage through the bus.
• There are two parts of it:

1. Measurement
2. Protection

Isolator

• The use of this isolator is to protect the transformer and the other instruments in the line. The isolator isolates the extra voltage to the ground and thus any extra voltage can't enter the line.
• Thus an isolator is used after the bus also for the protection.

Bus Bar

• The bus bar is a line in which the incoming feeders come into and get into the instruments for further step up or step down.
• A bus bar in electrical power distribution refers to thick strips of copper or aluminium that conduct electricity within the switchboard, distribution board, substation or other electrical apparatus.
• The size of bus bar is important in determining the maximum amount of the current that can be safely carried. Bus bars are typically either flat strips or hollow tubes as these shapes allow heat to dissipate more efficiently due to their high surface area.
• The skin effect makes 50-60 Hz AC bus bars more than 8 mm thick inefficient, so hollow or flat shapes are prevalent in higher current applications.
• Neutral bas bars may also be insulated. Earth bus bars are typically bolted directly onto any metal chassis of their enclosure.

Controls and Relay Panel

• The control and relay panel is if cubical construction suitable for floor mounting.
• All protective, indicating and control elements are mounted on the front panel for the ease of operation and control.
• The hinged rear door will provide access to all the internal components