# Mr Electro

Hi Mr Electro family!! This is an educational website for electrical stream ( Electrical engineering, Diploma student and PreDiploma students) . This is mainly focused for those students who are waiting for Government jobs like LokSewa Aayog PSC, NEA, CANN NTC for level 3, level 4, level 5 and level 7 and also private jobs.

## Friday, March 31, 2023

Current transformer (CTs) are essential components in power systems, used for measuring electrical current flowing in conductors. CTs are used in a variety of applications, including protection, metering, and control. In this article, we will discuss the basics of current transformer, how they work, and the factors that affect their performance.

# What is a Current Transformer ?

A current transformer is a type of transformer that is used to measure electrical current in a conductor. A CT is connected to the conductor, and the electrical current flowing through the conductor induces a current in the CT's secondary winding. The CT's secondary winding is connected to a measuring instrument or a protective relay, which is used to monitor or control the electrical system. Current transformers are designed to operate at a specific frequency, typically 50 or 60 Hz. CTs can be used to measure both AC and DC current, although AC current measurement is more common.

### How Does a Current Transformer Work?

A current transformer works on the principle of electromagnetic induction. When an AC current flows through a conductor, it creates a magnetic field around the conductor. The strength of magnetic field is directly proportional to current flowing through the conductor. The current transformer is designed so that the conductor to be measured is passed through the core of the transformer. The core of the transformer is made of ferromagnetic material, which increases the strength of the magnetic field around the conductor.

The core of  transformer is divided into two parts: primary winding and secondary winding. The primary winding is connected in series with the conductor to be measured or the conductor acts as primary winding, while the secondary winding is connected to a measuring instrument or a protective relay. When an AC current flows through the conductor, it creates a magnetic field that induces a current in the CT's primary winding. The current in the primary winding creates a magnetic field around the core of the transformer, which induces a current in the secondary winding. The current induced in the secondary winding is proportional to the current flowing through the primary winding.

The secondary winding of a current transformer is designed to provide a current output that is proportional to the current flowing through the primary winding. The output current is typically much smaller than the input current, with a typical ratio of 1000:1 or 2000:1.

### Factors Affecting Current Transformer Performance

Several factors can affect the performance of a current transformer, they are:-

Saturation: Current transformers are designed to operate within a specific range of currents. If the current flowing through the conductor exceeds the rated current of the CT, the core of the transformer can become saturated. When the core is saturated, the output current will not be proportional to the input current, resulting in inaccurate measurements.

Burden: The burden of a current transformer is the total load that is connected to the secondary winding of the transformer. If the burden is too high, the output current of the CT will drop, resulting in inaccurate measurements.

Accuracy Class: Current transformers are designed to meet specific accuracy classes, which define the maximum deviation in the output current from the actual current flowing through the conductor.

Frequency: Current transformers are designed to operate at a specific frequency, typically 50 or 60 Hz. If the frequency deviates from the rated frequency, the output current of the CT may not be proportional to the input current.

### Applications of Current Transformer

Current transformers are used in a variety of applications, they are:-

Protection: Current transformers are used in protective relays to detect faults in the electrical system. When a fault occurs, the current flowing through the system can increase to dangerous levels. The protective relay uses the current transformer to detect the fault and trip the circuit breaker to isolate the faulted section of the system.

Metering: Current transformers are used to measure the current flowing through power lines. By stepping down the current from a high value to a lower value, CTs enable meters and instruments to accurately measure the current without being damaged by high currents.

Energy Management: CTs are used to monitor energy consumption and demand in power systems. They enable accurate measurement and recording of electrical energy usage, which can be used for billing and energy management purposes.

Fault Diagnosis: CTs are used to detect and diagnose faults in power systems. By analyzing current waveform data, it is possible to identify and locate faults, such as broken conductors, open circuits, and short circuits.

Control: CTs are used in conjunction with power controllers, such as variable speed drives and thyristor controllers, to control the flow of current in power systems.