What Is CT PT Transformer - ElectricalGang

Hello friends, in today’s article we are going to talk about CT and PT transformers and how they work.

In This Post

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• What are CT and PT transformers called?
  • What is CT & PT?
  • What is CT?
  • Why a Current Transformer Is Used?
  • How CT works?
  • What is the CT Ratio?
  • What is PT?
  • How to work PT?
  • What is the PT Ratio?
  • Difference between CT and PT

What are CT and PT transformers called?

Friends, if someone asks you in an interview what CT and PT are, you can tell them that they are one type of instrument transformer.

Full names of CT and PT

CT: Current Transformer. PT: Potential Transformer.

CT and PT are a type of transformer used only in AC power.

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What is CT & PT?

CT and PT are both measuring devices used to measure currents and voltages. CT and PT are used where large quantities of currents and voltages are used. The job of CT and PT is to reduce high current and high voltage to a parameter. With the help of this parameter, we can measure the current flowing at high volume and voltage.

What is CT?

CT is a homogeneous current transformer that works to reduce the current flowing in the electrical system.

Why a Current Transformer Is Used?

This is used to measure the current when a large amount flows through any system.

Here we cannot use a clamp meter as each device has a limit on how much current it can measure. Because of this, if we want to measure a large amount of current, we have only one device that makes this work possible, which is called a current transformer.

Example: If you have ever measured a current using a clamp meter, let me tell you that the object on the top of the clamp meter is called a CT, or current transformer.

But this CT is very small and its working capacity is very low so it cannot be used in a big line.

How CT works?

The current transformer has a ratio that we call the CT ratio. As we know, CT works to reduce the current, so to know how much current this CT will give us by reducing the current, a ratio is written on it which we call CT ratio.

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What is the CT Ratio?

With the help of the CT Ratio, we can understand how much current we have by reducing our CT.

Example: Just like a current transformer has a ratio of 1000/5, this means that when 1000 A current flows out of the system, CT changes it from 1000A to 5A and we give the output.

What is PT?

PT’s full name is Potential Transformer. Right now we talked about the function of CT. PT also works today but with Voltage.

How to work PT?

PT gives us a low voltage in the output by lowering the high voltage. PT is used in large transmission lines. This is because more voltages are used in the high transmission line.

As we know with the help of any meter, we cannot measure the voltage of 33 kV or 220 kV. So this time we use PT. And switching from high voltage to low voltage. And we measure this output with the help of PT.

What is the PT Ratio?

Just like the CT par ratio is written, the ratio is also written on it which is called the PT ratio.

Example: 1000/5 as CT converts 1000A to 5A. So PT also has a ratio. If a PT cross is written as 11000/110 then this means that PT gives us 110 out of 11000 Voltage output.

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Difference between CT and PT

• CT is used to measure current while PT is used to measure voltage.
• CT is connected in series while PT is connected in parallel.
• CT ratio range is from 1 to 5A while the PT range is from 110V.
• We connect the output parameter from CT to the ampere meter and the PT output to the voltmeter.

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