What are Instrument Transformers?

In electrical engineering and power system, accurate measurements plays very important role. From monitoring power flow to protecting equipment, precise data plays a vital role in ensuring the reliability and efficiency of electrical networks.

In the field of electrical measurements , use of these instrument transformers is very important.

Instrument transformers play a vital role in accurately measuring high currents and voltages, enabling safe and efficient operation of electrical systems.

In this article, you will learn the principles behind current transformers (CTs) and potential transformers (PTs), shedding light on their design, working principles, all from your GATE Exam perspective.

What are Instrument Transformers ?

Instrument Transformers is used in AC system for measurement of electrical quantities i.e. voltage, current , power , energy, power factor and frequency .

For measuring higher amount of current and voltages we use transformers in conjunction with the measuring instruments. These measuring instruments is nothing but the instrument transformers.

Importance of Instrument Transformers

Instrument transformers is used to extend the range of measuring instrument.

It is also used to isolate the measuring instrument from high voltage line.

The Instrument transformers are of great importance for several reasons:-

i) Measurement Accuracy – Instrument transformers are crucial for achieving accurate measurements of current and voltage in electrical systems.

ii) Safety – Instrument transformers enhance safety by isolating measuring instruments and protective devices from high currents and voltages. They provide a low-voltage, low-current secondary circuit for instrumentation, ensuring the safety of personnel and equipment during measurement and control operations

iii) Equipment Protection – By accurately monitoring current and voltage levels, instrument transformers contribute to the protection of electrical equipment and machinery.

iv) Power System Control – Instrument transformers are essential for effective power system control and management. They provide data for voltage regulation, load monitoring, power factor correction, and energy management systems.

Instrument transformers enable accurate measurements, enhance safety, protect equipment, facilitate power system control, support grid monitoring and analysis, and assist in instrument calibration.

Their importance lies in their ability to transform high currents and voltages into manageable levels, making it possible to obtain reliable data and ensure the optimal performance, safety, and efficiency of electrical infrastructure.

Types of Instrument Transformers

There are two types of instrument transformers.

i) Current Transformers

ii) Potential Transformers

i) Current Transformers :- Current transformers is used to step down the current of power system to a lower level.

The current transformers produces low current on its secondary side. It is proportional to the high current flowing in its primary side. The primary coil is connected to the main supply and the secondary coil is connected to the ammeter. The ammeter is of very low range.

Let us understand this with the help of circuit diagram.

There are two windings primary winding and secondary winding . Primary winding is connected to the main supply and secondary winding is connected to the the ammeter. The no. of turns in the primary winding is very less as compared to the secondary side.

As primary winding is connected to the main supply , so it will carry the large amount of current . Therefore, the winding is made up of thick wire. The primary coil is always connected in series with the line.

Secondary winding has more no. of turns as compared to the primary windings. As it is connected to the ammeter of low range, a small amount of current flows through it. So, the secondary coil is made up of thin wire.

The current flowing in the secondary side is directly proportional to the primary side current. Current Transformers find extensive application in various fields, including power generation, transmission, and distribution, as well as in industrial systems, electrical substations, and energy management systems.

Current transformers are essential devices that facilitate safe and accurate current measurement in electrical systems. Their ability to transform high currents into proportional secondary currents allows for reliable monitoring, control, and protection of power networks, contributing to the efficient and secure operation of electrical infrastructure.

ii) Potential Transformers :- Potential transformers is also called as the step down transformers. In potential transformer, the voltage can be easily measured with low range voltmeter.

Let us understand with the circuit diagram.

There are two sides. Primary side and secondary side. The primary side is connected to the main supply. The secondary side is connected to the voltmeter. The voltmeter measures the voltage upto 150 V. In the potential transformer, the no. of winding in the primary side is more as compared to the secondary side.

With the help of current transformer and potential transformer we can step down the voltage and current to the lower value so that our instrument can directly measure the higher amount of current and voltage flowing in the network.

Summarizing it , we can say that the current transformer is used to measure the current and the potential transformer is used to measure the voltage. In this way , we use Instrument transformer to measure the higher amount of current and voltages in the network.

Lastly let us conclude this article by understanding the difference between Current and Potential Transformers.

Sr. No.	Current Transformer	Potential Transformer
1.	Secondary is connected to the ammeter.	Secondary is connected to the Voltmeter.
2.	Primary current depends on power circuit current.	Primary current depends on secondary burden.
3.	Primary winding has very less no. of turns.	Primary winding has large no. of turns.
4.	It is also called as series transformer as its primary coil is connected in series with the main supply.	It is also called as Parallel transformer as its primary coil is connected across the line .

Hope, so, this article has delved you with the significiant importance of instrument transformers and its types.