1. ACTIVE LEARNING ASSINGNMENT
SIGMA INSTITUTE OF ENGINEERING BAKROL,VADODARA DEPARTMENT OF ELECRTICAL ENGG .
ACTIVE LEARNING ASSINGNMENT
TOPIC ON:
CURRENT TRANSFORMER
SUBMITTED BY-
Kumbhani Alpesh ( )
Bakori Bhoomi ( )
Bariya Ranjit ( )
Guided By-
Priyank Shah
Assi. Prof.

2. OVERVIEW Introduction Structure Transformerloading(1)
Equivalents circuit of C.T.
Saturations
Safety precaution
Advantages.
Disadvantages.
Application.

3. INTRODUCTION
Current transformer or CT is a type of instrument transformer that is used in power system for measurement, detection, and protection the system.
It is a device used to measure large current by scaling large primary currents to a smaller, easy to measure, secondary currents.
In power distribution system, high voltage and high intensity of current always present.
Special instruments are needed

4. STRUCTURE Split-Core Type CT The split-core type CT is a special case
There are four basic types of current transformers:
window-type CT
contain no primary winding. Instead, the
wire that carries the current is threaded
through a window in the toroidal transformer.
Bar-Type CT
The bar-type CT is a window-type
CT with a primary bar inserted straight
through the window.
Split-Core Type CT
The split-core type CT is a special case
of window-type CT. Its winding and core
construction is such that it can hinge
open, or totally separate into two parts
Wound CT
consist of an integral primary winding
that is inserted in series with the conductor
that carries the measured current.
Donut-shaped CT(window-type CT)
Bar-type CT
Split-core type CT

5. TRNSFORMER LOADING (1)
AC voltage source sets up a flux in the coil core The exchange flux (F0) induces voltages (E1 andE2) in both coils. E1 and E2 are related as the number of windings n1 and n2. The load current (I0) is very small as long as E1 and U1 almost cancel each other

6. TRNSFORMER LOADING (2)
Resistance causes coli current I2 through coil 2 and current I1 flow through coil 1 Since I1 x n1 = I2 x n2 , induced flux 1 & 2 cancel each other. I1 and I2 are inversely proportional to number of turns of n1 and n2

7. EQUIVALENT CIRCCUIT OF A CT
X1= Primary leakage reactance

8. SATURATION
The plot shows the relationship between changing magnetic field strength
(H) and associated changing flux density / magnetic induction (B)

9. SAFETY PRECAUTIONS
It is important to ensure that the secondary of any CT is not left disconnected while the primary supply is on.
In this condition, high voltage spikes are produced in the transformer secondary, often thousands of volts, sufficient to break down the transformer insulation, or affect the accuracy of the transformer.
Hence the secondary of current transformer is never left open.

10. Advanteges of CT
It’s not possible to use the ammeter of normal current rang to measure very high current.
The user is safe due to the isolation provided by the current transformer between high current primary and low current secondary.
The C.T. Can be used to operate indicatting and protecting devices such as relays.
The same C.T. Can be used to provide the measured current to several instruments.

11. Disadvantages' of C.T.
It can be use to measure only ac current. The dc current can’t be measured.
C.T. Can’t be operated with open circuited secondary

12. APPLICATIONS
Current transformers safely isolate measurement and control circuitry from the high voltages typically present on the circuit being measured.
They are commonly used in the electrical power industry for:
Measurement:
measure current for power measurement and control. (In this case, accuracy is very important.)
Protection of power system:
perform circuit control, perform roles for safety protection and current limiting.

13. Current Transformers in measurement application:
110 kV grid

14. CTs used in power control circuit:
Circuit Breaker

15. THANK YOU