What is the difference between a CT and a transformer?

The main difference is current carrying capability. Transformer can handle upto thousands of ampere.

Current transformer(CT) is also a type of transformer which is designed in such a way that it increases voltage or reduces the magnitude of current(generally 1 to 5 ampere).

To start with, both are instrument transformers basically used for measurement and protection purpose in power systems. Below are few differences.

Current Transformers (CT):

The Primary winding of a C.T have smaller number of turns than secondary.

The secondary of a C.T can not be open circuited on any circumstance when it is under service.

A CT may be considered as a series transformer.

The primary current in a C.T is independent of the secondary circuit conditions (burden/load).

The primary winding of the CT is connected in series with the line carrying the current to be measured. Hence it carries of the full line current.

With the help of CT, a 5A ammeter can be used measure a high current like 200A.

Potential/Voltage Transformers (PT/VT):

The Primary winding of a P.T have larger number of turns than secondary.

The secondary of a P.T can be open circuited without any damage being caused either to the operator or the transformer.

P.T may be considered as a parallel transformer.

The primary current of a P.T depends upon the secondary circuit conditions (burden/load).

The primary winding P.T is connected across the line of voltage to be measured. Hence the full line voltage is impressed across its terminal.

With the help of P.T, a 120V voltmeter can be used to measure very high voltages like 11KV.

Symbolic difference:

Wiring Connection difference:

Transformer:

Transformer is a static electrical device which transforms electrical energy from one circuit to another without any direct electrical connection and with the help of mutual induction between two windings.

It transforms power from one circuit to another without changing its frequency but may be in different voltage level.

Current Transformer(CT):

A current transformer is a device that is used for the transformation of current from a higher value into a proportionate current to a lower value.

It transforms the high voltage current into the low voltage current due to which the heavy current flows through the transmission lines is safely monitored by the ammeter.

Current transformers can reduce or "step-down" current levels from thousands of amperes down to a standard output of a known ratio to either 5 Amps or 1 Amp for normal operation.

Functions:

Current transformers perform the following functions:

Current transformers supply the protective relays with currents of magnitude proportional to those of power circuit but sufficiently reduced in magnitude.

The measuring devices cannot be directly connected to the high magnitude supplies. Hence current transformers are used to supply those devices with currents of magnitude proportional to those of power.

A current transformer also isolates the measuring instruments from high voltage circuits.

Difference Between Voltage Transformer and Current Transformer

Definition

The voltage transformer is a style of electrical conductor that is used to convert voltage from an upper to a lower value. The potential transformer's main remains attached to the line to measure the line voltage.

The outdoor low voltage transformer decreased the high voltage value to a minimal amount that may be easily detected using a voltmeter.

On the other hand, a current transformer is a device that is used to convert the current from a more excellent value to a lesser value compared to the ground potential. It has been used with AC devices to measure high current values.

The current flowing is very high, and measuring it directly is challenging. Thus, a current transformer is employed to convert a high value of the current into a proportional number.

Core

In both constant voltage transformers and outdoor low voltage transformers, the core type of the instrument can be utilized for high and low voltages. Its core is made of quality materials and can operate at a low density to magnetize small currents.

Basically, the stainless steel laminations owned by the core of a current transformer are used to construct the transformer's core. Meanwhile, the core of a potential functional transformer is built up of a high functioning core that operates at low current concentrations, which allows it to work efficiently.

Primary Winding

Voltage transformers are capable of turning the windings in a large number. However, it only has a thin conductor. Meanwhile, the primary windings of a current transformer are typically in a single turn. It is thick as to how the heaviness of the conductor is capable of tolerating high-type currents.

Secondary Winding

The secondary windings of constant voltage transformers are not the thick kinds of conductor, so it has fewer turns. On the other hand, the current transformer is a thin type of conductor capable of turning in a number of turns. It can also carry a 5A-20A.

Applications

Voltage transformers (may it be low voltage transformer or high voltage transformer) focuses on the power source, measurement, and operating a protective relay. The current transformer, on the other hand, focuses on measuring the power and current. It also monitors the power grid operator for a functional and secured relay.

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