Introduction of a substation
• Intermediate link between Generating station & Consumers.
• An Electrical Substation is a subsidiary station of an electricity Generation, Transmission And
Distribution System where voltage is transformed high to low or reverse using transformer.
• Examples of Substation:-
33/11KV TT Nagar Substation
Established in 2002.
This substation is used 33KV as input and converted it into 11KV through Power transformer.
Approximate 52000 people of Tatya tope nagar and Ambedkar nagar get the electricity from
In this substation there are 3 substation operator, 3 line man under 1 JE.
In 2004 Meharbaan Singh Ka Purva was added with TT Nagar Substation with the same 33KV
132KV incoming 11KV outgoing
132KV is step down to Tatya tope Nagar
33KV in Barra 8 and Ambedkar Nagar
then get as incoming 16 Village
33KV in TT nagar, 33KV is
supplied to Meharbaan Singh Ka
Equipment used in Substation
Fire fighting system
Lightening arrestors are the instrument that are used in the incoming feeders so that to
prevent the high voltage entering the main station.
To prevent any damage lightening arrestors are used.
Potential Transformer (P.T)
Potential transformers used in the bus connected both side of the bus.
The potential transformer uses a bus isolator to protect itself.
The main use of this transformer is to measure the voltage through the bus.
To get the detail information of the voltage passing through the bus to the instrument.
It steps down the current level of the line for following purposes:
CT’s are basically used to take the readings of the currents entering the substation.
This transformer steps down the current from 800 amps to 1 amp.
Carry electrical supply
Isolator is the devices used to protect the S/S from any fault on the incoming feeder.
They are also helpful while maintenance is to be done in substation.
The main function of the insulators is to provide perfect insulation between the live conductors
and the supports.
Types of Insulators are
Pin type insulators
Suspension type insulators
A circuit breaker can make or break a circuit either manually or automatically under no load, full load or
short circuit conditions.
Circuit Breaker are of
Oil Circuit Breaker
Vacuum Circuit Breaker
SF6 Circuit Breaker
Air Blast Circuit Breaker
Oil Circuit Breaker
Oil circuit breaker which employ insulating oil for arc extinction.
Buchholz Relay is also used to protect the P.T.
SF6 Circuit Breaker
In this hexafluoride gas is used as arc quenching medium.
The SF6 is an electro-negative gas and has a strong tendency to absorb free electrons.
These are the devices that detect the fault and initiates the operation of the circuit breaker
to isolate the defective element from rest of the element.
They are basically of two types
It is used to protect the system from extra voltage.
Types of grounding are
But commonly people used the
mixture of coal and salt and coal,
as a grounding material.
Transformer’s are basically used to step up and step down and vice versa.
Now basically small substation used transformer to reduce the voltage or step down the
It is easier to installed single three phase transformer instead of 3 single phase transformer.
In This Power Transformer from the incoming 33KV is Provided and we get 11KV as O/P after
It’s rating is 10MVA, we can also used 3.15MVA or 5MVA rating of transformer.
In 33/11KV substation delta-star connection’s are used.
This is used for protection and cooling purpose.
It’s mineral oil obtained by refine crude petroleum. It serves the following purpose.
Provide additional insulation.
Carries away the heat generated in the core & coils.
Protects the paper from dirt & moisture for this Breather is used.
Transformer oil is very costly.
Maintenance of Transformers
Check Oil level in main tank.
Check the colour of silica gel in breather.
i. It must be blue in colour.
ii. If it is turns pink then replace.
Check On load Tap Changer Lower/Raise trail by Local & Remote.
Trip trail by draining oil in Buchholz relay.
Check Earth resistance ,provide watering arrangement for earthling pits.
Clean the bushings.
Attend the oil leakages.
Note Temperature of Oil & leakage.
Batteries are used in substation as an auxiliary power supply to provide power for
lightning, heating ventilation and communication equipment.
Several batteries are connected in series.
All latest equipment’s are now also design as they can operate with DC voltage also.
This is first part of protection or controlling.
This type of equipment is directly linked to the reliability of the electricity supply.
It act as controller to control the output supply.
This is also used to know how much power is consumed in the area as well as in
To repair any faulty part firstly isolate from control room then through isolator which is
Fire Fighting System
This is used to protect the equipment’s of the substation from any accident.
Basically Dry Carbon-Di-Oxide is used.
But sand is also used for instant protection.
Tripping – Power goes due to over load. It is for the protection of components.
Shut down – Power is cut due to maintenance in progress. It is done manually.
Break down – Power goes due to any fault in the line. When fault is removed , power is
Roasting – Power is cut deliberately on order of higher authority due to shortage of
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