A Project Report on Inrush

7/31/2019 A Project Report on Inrush

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A Project Report On

Modeling And Analysis OfInrush Current In Different

Conditions


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Submitted By

Bibek Ranjan Dutta

Roll no-08176016007

Koushik Karmakar

Roll no-08176016001

Subhojit Dawn

Roll no-08176016021

Sudip Kumar Samanta

Roll no-08176016003


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Introduction

When a power transformer is energized there is an important transient

inrush of current that is necessary in order to establish the magnetic field

of the transformer. Some power transformers exhibit peak current

demand up to six or thirty times the nominal value. Such high values of

current in power devices like transformer is known as INRUSHCURRENT.

The transient magnetizing inrush current in a transformer is produced by

saturation in the transformer core. This current, which is characterized as

being almost entirely unidirectional, rises abruptly to its maximum value

in the first half-cycle after the transformer being energized and,

thenceforth, decays until the normal steady-state magnetizing conditions

in the transformer are reached.


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Inrush


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Effects Of Inrush

This inrush currents involves a large and long lasting dc component, which

is rich in harmonics, assumes large peak values at the beginning about 6 to

30 times of the rated value. This condition causes unbalance of current

loop of differential relay that will occur with mal-trip.

In order to prevent false tripping due to an inrush current, identification

of short circuit current and inrush current should be made and a

comparative study should be done to understand the effects of different

parameters on this inrush current.


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Parameters That Affect Inrush

The magnitude and duration of the inrush current depend basically on:

Circuit breaker switching

Source Voltage

The value and sign of the residual flux linkage in the transformer core

The saturation characteristic of the transformer core

The total impedance of the circuit through which the inrush current flows

Active & reactive power demand of the system

Distance between the bus of the substation and the power transformer


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Our work

Case1: Varying source voltage (breaker time and load fixed)

Case2: Varying load (source voltage and breaker time fixed)

Case3: Varying breaker time [initially open](source voltage and load fixed)


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Simulation Model


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Transformer Parameter


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Voltage = 500e3/sqrt(3)*sqrt(2)


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Voltage= 300e3/sqrt(3)*sqrt(2)


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Voltage=100e3/sqrt(3)*sqrt(2)


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Active power P (W)=36.7e6; Capacitive reactive

power Qc (negative var)= 62.7e6


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Switching times (s)= [ 1/50 ]


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Conclusion

The amplitudes of the inrush currents, calculated with the simulation

model, clearly indicate that for the considered 3cases, in all of them the

inrush current contained a large and long lasting dc component, which is

rich in harmonics and especially 2nd order harmonic was more dominant.

However, one aspect of this analysis which has been largely ignored in the

relevant context is the effect of the inrush current may cause on potential

transformers already in operation , and vice versa. Also some techniques

for reduction of transformer inrush current should be developed in future

work.


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Thank You

A Project Report on Inrush

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