Current Transformer

Product Description

Current Transformer

There are following types and sub types of C.Trs.

L.T Tape wound/Cast Resin type CT.

Sub type

• Ring/window type and
• wound primary type

L.T/H.T Cast Resin CT.

Sub type

• Ring/window type and
• wound primary up to 33 KV with Indoor/ Outdoor application.

H.T Indoor / Outdoor Oil Immersed type C.T/ P.T up to 132kV

Function of Current Transformer

The main function of the Current Transformer is to reproduce the Primary current on its secondary side. The Current Transformer isolates the devices connected to their secondary circuit from the network system. Current Transformers are specially designed for measuring and protection applications.

Standard Range

We manufacture a comprehensive range of standard C.Trs. for measuring and protection application as per IS 2705/IEC 60044. The standard range is from 5/5A to 5000/5A

Standard Terminology used for CT:

Rated primary current:

The Current to be measured and transformed to lower value

Rated secondary current:

The current on the secondary side of the CT Typical values of secondary current are 1A or 5A. For WTI Current Transformers 3 A secondary current is also specified. For special differential protection, secondary currents of 1/Rt3 or and 5/Rt3 are also specified.

Rated Transformation Ratio:

The transformation ratio is the ratio to which the primary current is to be reduced to a measurable value. The standard transformation ratio is/5or/1A.

Rated burden:

The load of the secondary circuit in Volt-amperes at the rated secondary current and at specific power factor (0.8 or 1)

Accuracy class:

For metering CT s, accuracy class is typically 0.2,0.5,1 or 3. This means that the errors have to be within the limits specified in the standards for that particular accuracy class.

The metering CT has to be accurate from 5% to 120% of the rated primary current at the specified power factor.

Selection and Application of Current Transformers As pertable I land II.

In the case of protection CT s, the CT s should pass both the ratio and phase errors at the specified accuracy class, usually 5P or 10P, as well as composite error at the accuracy limit factor of the CT.

Measuring Current Transformers

Class

Application Table

• 0.2 For Very Accurate power Measurement & tariff metering.
• 0.5 For accurate power Measurement & tariff metering.
• 1.0 For meters, measuring power, current & voltage.
• 3.0 For ammeter or voltmeter.
• Following are the VA burdens as per IS:2705 :
• 2.5, 5, 7.5, 10, 15 and 30 VA.

Following are the VA burdens imposed by meters :