Current Transformer (CT) Details.
A current transformer C.T is a device that is used to measure alternating current. Many may ask why I am using a current transformer if current can be measured with a multimeter! Current transformer CT are mainly used for measuring high current.
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We know that high power lines have a lot of currents. In this case, an ordinary emitter or multimeter cannot measure this current. This is why current transformers are used. The basic principle of a current transformer is a lot like a normal power transformer.
P.T Potential transformer
Power transformers
Like power transformers, current transformers also have primary and secondary windings. When power is supplied to the power transformer, the current starts flowing through the primary winding, generating alternating magnetizing flux which is induced alternating current in the secondary winding.
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And let me explain a little, when the primary coil is supplied with electricity, a magnetic field is generated around it which collects the secondary coil. The result is mutual induction between the primary and secondary coils and electricity flows in the secondary.
The number of turns in the primary winding is very low and the number of turns in the secondary winding is high. An ammeter is attached to the secondary winding to measure the current.
The question may be, why the number of turns in the secondary winding is less than in the primary winding? It has a specialty which we will know in the procedure below.
Operation of the current transformer.
Current transformers usually step up in case of voltage and step down in case of current. Many may question why the current transformer is step up in case of voltage and step down in case of current. As I said above there is a specialty that we will know right away.
How to reduce system loss.
Does everyone remember Lenz’sformula? If not seen again, the induced electric current flowing through the conductor wire creates a magnetic field around the conductor wire, which prevents the origin of the induced current from occurring in it (i.e. the changing magnetic field).
That is, in the case of current transformers, the number of secondary turns is higher, so according to Lenz’s formula, the current in the secondary will be more constrained than the primary and secondary sources.
We know
I1N1 = I2N2
I1 / I2 = N2 / N1
I1 / I2 = n
Where,
I1 = primary current
I2 = secondary current
N1 = number of primary punches
N2 = number of secondary punches
n = ratio of primary and secondary punch numbers.
Usually current transformer and ammeter are used together which you can understand by looking at the image above. The ratio of most current transformers is 100/5. In other words,
the primary current is 20 percent more than the secondary. So when the current flow in the primary conductor is 100 amperes, the current in the secondary winding will be 5 amperes.
Again in the case of 500/5 amperes, 500 amperes will generate a 5-ampere current in the secondary for the primary conductor which is 100 percent more in the primary.
The secondary of the current transformer should not be kept open.
Under normal conditions in the city, according to Lenz’s formula, the primary and secondary windings form magnetic fluxes and bind to each other.
The secondary magnetic flux is less than the primary magnetic flux and the net magnetic flux is much less. This net acts on the core of the magnetic flux current transformer. When the secondary winding of the city is kept open then the secondary current will be zero where the primary current of the city will remain the same.
In this case, there will be no constraining magnetic flux in the secondary. Therefore the net magnetic flux N1I1 for primary current only is much higher. This more magnetic flux will create much more flux in the core which will take the core to the saturation level.
Due to too much flux
Due to too much flux in the core, the flux linkage at the secondary winding will be much higher which will generate much more voltage at the secondary terminal of the city. This too much voltage is very harmful to the second terminal and it will cause insulation failure and accidents can happen.
If there is flux in the extra core, hysteresis and eddy current loss will be much higher and the temperature of the city will also increase. As the oil fills up in the city, the oil will continue to boil (boil) and evaporate due to the extra temperature. As a result of evaporation, the city’s housing will put a lot of pressure and will explode. This type of blasting will cause fire and smoke.
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