Novel FUZZY and Series Transformer based

Fault Current Limiter

R.jeyapandiprathap,M.E.,AP/EEE ,M.Siva Kumar, K.K.Venkatsabari,K.SeemanKlnce, Madurai

Abstract: Developing power system networks and

their interconnections may increase the short-circuit

levels beyond the capacity of circuit breakers (CBs).

Short-circuit fault can cause overvoltage transients,

loss of synchronization. This paperproposes a novel

transformer-based solid state fault current limiter

(TBSSFCL) for radial distribution network

applications. The proposed TBSSFCL is capable of

controlling the magnitude of fault current. In order to

control the fault current, primary winding of an

isolating transformer is connected in series with the

line and the secondary side is connected to a reactor,

paralleled with a bypass switch which is made of

anti-parallel insulated gate bipolar transistors. By

controlling the magnitude of ac reactor current, the

fault current is reduced and voltage of the point of

common coupling is kept at an acceptable level.

Also, by this TBSSFCL, switching overvoltage is

reduced significantly.

I INTRODUCTION

Inpowersystemdesignview,limitingthefaultcurrentto

alowlevelcan

reducethedesigncapacityofsomeelectricalequipment

inthepowersystem.Thiswillleadtothereductiontothei

nvestmentcostforhighcapacitycircuitbreakers

andconstructionofnewtransmissionline.Consequentl

y,frombothtechnicalandeconomicalpointsofview,fa

ultcurrentlimitingtechnologyforreducingshortcircuitc

urrentisneeded.

FCLisavariable-

impedancedeviceconnectedinserieswithacircuittolim

itthecurrentunderfaultconditions.TheFCLshouldhav

everylowimpedanceduringnormalconditionandhighi

mpedanceunderfaultcondition.Onthebasisof

theabovecharacteristic,varioustypesofFCLhavebeen

developed.Someofthese

FCLarebasedonsuperconductor,powerelectronic

switchesandtunedcircuitimpedance.

Thefaultcurrentlimitingtechnologyhasbeco

mehotspotinpowersystem

protectionresearch.However,theresearchareconcentr

atedonthesuperconducting

andpowerelectronicswitchestypesofF

Overthelastfourdecades,differenttypesofFCLshavebe

enunderthe

spotlightinpowerprotectionresearch.Inrecentyears,va

rioustypesofFCLhave

beenproposedanddevelopedinmanycountries.Mainlytw

otypesofthemare

discussedmost.Oneissuperconductorfaultcurrentlimit

er(SFCL),theotherone

issolidstatefaultcurrentlimiter(SSFCL).Thisinterestc

omesnotjustduetotheir

excellentcurrentlimitingcharacteristicsbutalsoduetot

heirpositivecontribution

tothequalityofsupply.FCLscanbeeffectiveinreducing

supplyoutageandmitigatevoltagesagonpowernetwork

.

FaultCurrentLimiter FCLsisadevicethathaspotentialtoreducefaultlevelont

heelectricitypowernetworksandmayultimatelyleadtol

owerratedcomponentsbeingusedortoincreasedcapaci

tyonexistingsystems.Electricityindustryisveryattract

edinsuchdevices,providingthatFCLofferthemsatisfa

ctionineconomicsaspectaswell

astechnicalconstraints.

II PROPOSED WORK

Developing power system networks and their

interconnections may increase the short-circuit levels

beyond the capacity of circuit breakers (CBs). Short-

circuit fault can cause overvoltage transients, loss of

synchronization. This paperpropose a novel

transformer-based solid state fault current limiter

(TBSSFCL) for radial distribution network

applications. The proposed TBSSFCL is capable of

controlling the magnitude of fault current. In order to

control the fault current, primary winding of an

isolating transformer is connected in series with the

line and the secondary side is connected to a reactor,

paralleled with a bypass switch which is made of

anti-parallel insulated gate bipolar transistors.

• fuzzy control logic used to control active

devices switching activities

• By controlling the magnitude of ac reactor

current, the fault current is reduced and

voltage of the point of common coupling is

kept at an acceptable level. Also, by this

TBSSFCL, switching overvoltage is reduced

significantly.

Block Diagram

Source Load

Gate DriverCurrent Measurement

Micro controller

LCD

Power

Supply

+5V

-5V

GND

Series Transformer

•M1- MOSFET 1

•M2- MOSFET 2

The basic configuration of the SSFCL

consisting of two connected solid state

switches with Series Transformer.

The M1 & M2 act as the Series transformer

switches.

Switches are connected in inversely serial

manner for both branches.

The corresponding firing pulse is generated

from the controller whenever the faulty

current flows through the load.

CIRCUIT DESCRIPTION

The proposed circuit diagram consists of our project

the power supply circuit the circuit is a dual power

supply (+5V,-5V). The output voltage goes to all IC‟s

operating voltage. The line current measuring devices

CT, the current transformer connect to the series of

the load. Current transformer output connects to the

Shunt resistor to drop the current and allow the

voltage.

The voltage signals goes to IC 741 pin 2. This

attenuator circuit increases the voltage. The output

signals go to microcontroller. Phase current signal go

to controller .The microcontroller is PIC 16f877A is

using of our project. The controller input analog

signals convert into digital signal.

The controller compares the input value and set

value. To increase the input signal the controller

output is high. As a same time the LCD display is

displaying the current. The controller output signal is

go to buffer. The buffer amplifies the signals. This

outputis connected to the opto coupler.

The optocoupler electrically isolate the devices.

Optocoupler output is connected to the Mosfetgate.

The gate pulse is high, Mosfet is switched ON. Also

if, SFCL switch is in ON condition means, if any

fault current flows the SFCL Mosfet will be ON. And

corresponding fault current will be limited through

the inductive load.

IV RESULT AND DISCUSSION

The proposed system was implemented with the help

of Simulink and simulted power system tool boxes in

the MATLAB R2013a software. The following figure

represents the following figure depicts the power

system network considered in this work.

Figure Simulink model of three phase power

system network with 3L-L fault

The aforementioned Simulink model is designed for

11kV distribution grid and the 11kV/415V three

phase transformer and it is connected with the 415V

bus and followed by the linear load. The three phase

L-L fault is added with the model ta the load side.

The Simulink model after adding the TBSSFCL in

series with the feeder line is shown in the following

figure 4.2

FigSimulink model of the power system with

TBSSFCL

The TBSSFCL is serially added with respect to the

feeder line from the main grid. The TBSSFCL is

responsible for limiting the over current from due to

presence of Fault on the load side. The Simulink

model for the TBSSFCL block is represented in the

following figure.

Fig Simulink model for TBSSFCL for single

phase line

The IGBTs present inside the TBSSFCL has to be

controlled very precisely in order to limit the fault

current as dictated at Chapter 3. The main control

block for controlling the IGBT is shoen in the figure

4.4. The circuit contains comparator cirucits and that

comparing the actual value of line current with the

referenece current and turning off the IGBT by

controlling its Gate pulse and parallelly limitinf the

high rate of fault current on the system .

Fig Simulink model for IGBT control block

The Gate pulse generated for the IGBTs in the

TBSSFCL is shown in the following figure. The Plot

represents that the L-G fault is injected between the

time intervals 0.002 to 0.004s. The control block

shown on the above figure produces the logic „0‟ at

the fault occurrence time. Hence by the IGBTs are in

the OFF state.

Fig generated gate Pulse for IGBT

The injected 3L-L fault current and voltage are

measured with the help V-I measurement block and

the corresponding waveforms are shown in the

following figure 4.6

Figure L-L fault voltage and current

The fault current limitation is analyzed on both load

side and source side and with and without TBSSFCL

block. The current waveforms on the source side with

fault on two cases ie.with and without TBSSFCL is

represents in the following figures 4.7 and 4.8

respectively.

FigSource side current with Fault & without

TBSSFCL

FigSource side voltage & current with Fault

&TBSSFCL block

The above waveforms demonstrates the importance

of TBSSFCL on the power system very clearly. The

source current and voltage are still stable during the

fault occurrence time period [0.002 to 0.004s]. By

this way the TBSSFCL supports the source side

stability at critical scenarios.

The voltage and current waveforms on the load side

with fault on two cases ie.with and without

TBSSFCL is represents in the following figures 4.9

and 4.10 respectively.

FigLoad Voltage & current with Fault & without

TBSSFCL

FigLoad voltage & current with Fault

&TBSSFCL block

The above waveformsdemonstrates the importance of

TBSSFCL on the power system very clearly. The

source current and voltage are still stable during the

fault occurrence time period [0.002 to 0.004s]. By

this way the TBSSFCL supports the source side

stability at critical scenarios.

V CONCLUSION

The project work has been completed

successfully. The project work works satisfactorily.

From the beginning we conducted many block wise

experiments and verified operation of all the blocks

individually and as a result we did not face much

difficulty in the final integration of the project. In an

attempt develop the project by the way we had the

opportunity to learn PC the concepts of PC based

system design and we also learned the basic concepts

of designing and fabricating SOLID STATE FAULT

CURRENT LIMITER. We also had an opportunity to

work in microcontrollers. This work helped us to

think constructively and led to inculcating a habit of

learning and hard working. We also realized the need

for innovative thinking. Finally we can say that the

entire venture into the development of the project

work was educative and interesting and we could see

many theories that we have learned through class

room lectures now work perfectly in a real world

application.

REFERENCES

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smart Grid “IEEE Transaction on applied super

conducting”,Aug2010.

[3] Woo-Jae Park, Byung chul sung, “The Effect of SFCL on

Electric power grid with wind-turbine generation system

“IEEE Transaction on applied super conductivity,

Vol.20,No.3,June 2010.

[4] Mark Stemmle “Analysis of unsymmetrical faults in high

voltage power systems with super conducting fault current

limiter, ”IEEE Transaction on applied super conductivity,

Vol.17,No.2, June 2007.