Electrical Transformers : Backbone of power stations

Hey guys, Welcome back to my blog. It is a beautiful day and another opportunity to explore the world of engineering.

One of the most challenging projects I have ever been involved with was during my internship with the transmission company of Nigeria in Ibadan and I was opportuned to be part of the team that installed a 150MVA 330/132KV transmission substation to increase transformer capacity at the station. It was a really tasking time but also a fantastic experience.
That experience gave me this deep love for electrical transformers. So today I would be focusing on the operation of an electrical transformer.

Now Let’s take a closer look at electrical transformers?

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Transformers definitely not the movie

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^{image of a me during the installation of the transformer behind me by @dannybravo94}

An Electrical transformer is simply an electrical device that transfers electrical energy by electromagnetic induction from one circuit to another. It is used to Step up or Step down Voltage without changing the frequency.

Why are transformers so important to power stations?

Transformers are one of the most important parts of power stations because they play a major role in reducing power loss. Power systems transformers are used to step up or step down voltages depending on the need.
For instance, with increase in voltage, current decreases, so to minimize transmission losses voltage is stepped up at the transmission end while at the distribution side the voltage is stepped down to the required level.

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How do transformers operate?

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^{image of a transformer at Ayede transmission station by @dannybravo94}

Transformers function based on this simple Principle which is when a fluctuating electric current flows through a wire, it generates a magnetic field or magnetic flux around it. The magnetic flux density is directly related to the size of the electric current. So the bigger the current the bigger the magnetic field.

That’s not All …Electricity is so cool, don't you think?

Also when a magnetic field fluctuates around a piece of wire, it generates an electric current in the wire, then when you put a second coil of wire next to the first one and send a fluctuating electric current to the first coil, we would create an electric current in the second wire.
Isn’t that fascinating? This concept is simply described as electromagnetic induction because the current in the first coil induced a current in the second coil.
So transformers work based on faraday’s law of electromagnetic induction which states that “Rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil”.

With this understanding, a Basic transformer has two types of coils:
PRIMARY COIL (the coil to which the supply is given)
SECONDARY COIL (the coil from which supply is taken from)

In order to make electricity pass through more efficiently from the primary coil to the secondary coil they are wrapped around a soft iron bar usually called a CORE. To make a curl of wires we curl them round into TURNS.
For instance, If the secondary and primary coil have the same number of turns, the electric current in both coils would virtually be the same.

But if there are more turns or lesser turns in the secondary coil than the primary coil, then we can make the secondary current or voltage bigger or smaller than the primary current and voltage respectively.
This concept ONLY works when the electric current is fluctuating in a way. So a constantly reversing electricity called Alternating current (AC) is used

Now, this brings US to step-up and step down transformers which I would explain briefly

STEP DOWN Transformers

In a Step down transformers the primary coil has more turns than the secondary coil.
As a result of this the secondary voltage is smaller than the primary voltage
while the secondary current is bigger than the primary current.

STEP UP TRANSFORMER

In a step up transformer the secondary coil has more turns the primary coil, hence it boasts a low voltage into high voltage.
As a result of this a bigger secondary voltage and a smaller secondary current is generated.

Now taking a closer look at both transformers you would realize that the coil with HIGHER number of turns would have HIGHER VOLTAGE, while the coil with FEWER turns have HIGHER CURRENT.
You see how simple and straight forward it is…

Now finally, the basic working of a transformer.
For a transformer to function these two processes occur

1. Whenever there is change in current flowing through the primary coil, magnetic flux is produced in the primary coil.
2. Change in the magnetic flux links with the secondary winding induces EMF in the secondary coil.
   However, the TURNS RATIO of the transformer determines the voltage produced in the secondary coil.
   This equation shows the relationship between voltages and the number of turns:
   N1/N2 = V1/V2 = I2/I1

Where N1, V1, I1 are the number of turns, voltage and current in the primary coil of the transformer respectively and N2, V2, I2 number of turns, voltage and current in the secondary coil of the transformer respectively

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CONCLUSION

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The role of transformers in power stations for transmission and distribution cannot be overemphasized and I am sure by now you understand why I love transformers with so much passion.
Just in case you are wondering why transformers are rated in KVA: Its simply because transformer losses depend only on current and voltage.
There you have it………

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REFERENCES

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electrical4u transformers

explain that stuff transformers
owlcation easy understanding of the transformer
Wikipedia transformer