protection of power lines using global sevice

8/10/2019 protection of power lines using global sevice

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Protection of

transmission linesusing GPS

Presentation by


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1. INTRODUCTION

A century haspassed since

theapplication of

the firstelectro

chemical over

current relaysin powersystem

protection.


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Distance protection has played an importantrole in power line protection since it was first

introduced in the early part of the century. It has many advantages over the power line

protection techniques and can be adopted forfault location and back up protection.

However , like other power frequency basedprotection techniques

With the continuous development of modern

technology, protection relays have advancedwith the development of electromechanical,semiconductor, integrated circuits andmicroprocessor technologies.


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History

since the concept was first raised in the late 6!s relaytechnology has gone through rapid development. Digitaltechniques for transmission line protection have been quicklydeveloped

"odern development for power system network , the demandfor fast fault clearance to improve system stability and the

need for alternative protection principles have resulted in thesearch for methods to increase the speed of relay response .

In the late #!s this led to the development of $ultra highspeed protection $ based on the use of traveling waves andsuper imposed components these relays offered the advantage

of fast response , directionality , and where not affected bypower swing and %& saturation. However many distinctadvantages of the conventional protection techniques wherenot retained for eg. Inherent back up protection.

In recent years, there is a growing interest in the use of faultgenerated transients for protection purposes


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Etensi!e researc" #or$

to develop new relaying principles and techniquesbased on there detection.. this led to the newconcept of $transient based protection $'&()*.Among these the $positional protection+ offers

attractive solutions for power line protection. the actual portion of the fault on the line by

measuring the traveling time of the high frequencytransient voltage or current signals along the line .

in contrast to the conventional traveling wavebased protection techniques, this techniqueconcentrates on the fault generated signals duringarcing and their associated high frequency signals.


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%unctionality

&he positional protection uses its associated )-scheme to determine the instant when it detects thefault generated high frequency transient signals anduses the power line communication system to

communicate this information to the relays at theother substations.

the system can also respond to the high frequencytransient generated by switch gear operation, whichprovides an immediate opportunity for comprehensive

self testing and calibration checking. lectro magnetictransient program'")&* software has been used tosimulate a model H/ transmission system in order toe0amine the response of the protection scheme to avariety of different system and fault condition.


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&. %'U(T GENER'TEDTR'NSIENTS 'ND

'SSOSI'TED PROTECTIONTECHNI)UES

A comparison of different protectiontechniques in the frequency domain is shownin fig . a power system fault indicates avariety of additional transient components inadditional components contain e0tensiveinformation about the fault and are spreadthrough out the spectrum ranging from Dc tomay kilohert1 and even mega hert1.


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In conventionalprotection scheme , thehigh frequency signalsare considered to benoise and filtered outand as a result,considerable researchhas been spent on thedesigning of the filters ,

protection schemesbased on detection offault generatedtransient, such as the $ultra high speed

protection + schemes aregenerally limited by theband width oftransducers used.


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&he transient based protectiontechnique operate by e0tracting thefault generated high frequencysignals through specially designeddetection devices and their

associated algorithms. &he highfrequency current signal aredirectly e0tracted from the %& outputs . although conventional iron

cored %&!s alternate the highfrequency signals.


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*. CH'RECTERSTICS O%HIGH %RE)UENC+ CURRENT

SIGN'(S

&he theoretical aspects of the characteristics

of the propagation of high frequency signals on transmission lines have been well documented.


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*.1 ,etection of fault -osition an,fault generate, current transients

when a fault occurs on a transmission line , wide bandvoltages and current signals propagate away from the

fault point along the power conductors.

, the fault position on the line , fault path resistance and

the characteristics impedance of the power conductors.this propagation can be shown graphically.

Here relays are located at all of the substations in the

power system and independently monitor the powersystem. The frequency range of interest for monitoring

these fault generated high frequency signals is between40!0 "H# and the signal processing is designed as to

determine the arrival of a high frequency transientcharacteristics of those generated by a fault.


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3.2 Fault currenttransient detector

&he proposed scheme uses a specially designed transientcurrent detector fed from the primary %&s . &his e0tractsare high frequency signals associated with the faultgenerated current transients. A simplified block diagram

of the detector arrangement is shown in the figure. &he detector is designed to interrogate signals in the

range of frequencies from 2345H1. analog circuit actsas a band pass filter which e0tracts the band of faultgenerated transient current signal from the line. as a

result , the response of the scheme is not affected by thepower frequency short circuit band at the busbar or thepresise configuration of the source side networks.


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*.* Signal Processing Unit

model transformation is employed todecouple the signal in to their respective aerialmodes. &he signal mi0ing circuit receive thesignal from the phase %&s and continue

these to form mode7 and mode signals. &he sampling frequency of the analog to

digital A8D converter is 9 "1 and the speed ofpropagation of the high frequency transient is

similar to the speed of light. &he digitalprocessing includes filters sequence recording,amplitude comparison, counters and decisionlogic.


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. /'SIC PRINCIP(ES'ND RE('+ DESIGN

A short circuit fault on apower transmission line

generates voltages andcurrent signals over a widefrequency range. &hey are

(asic )rinciple :elay Design


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.1 /asic Princi-le

&he basic principleof the technique canbe demonstrated by

referring to the25v, H/transmissionnetwork, shown in

figure.

yyyy


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4.2 Relay Design

A simplified blockdiagram of the relayunit is shown in fig..

the transient detectoruni;t is connected tothe line using threephase %/&s . these

are able to detect thefault generated highfrequency voltagesignals.


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0. ODE((ING 'ND SIU('TION

System o,eling2 &he response of the complete system

was evaluated by modeling the transmission line systemtogether with the relays in the scheme using the "&)

simulation program. simulation of line and transformer energi1ation , load

re


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Primary system

voltages

$elay responses


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3.Conclusion

A new technique for the protection of atransmission line network is presented inthis paper. &his uses a dedicated faultdetector to e0tract the fault generated

high frequency voltage transient signaland )- system to time tag these signals.

&he traveling time of the transient highfrequency signal from the point of fault tothe ad


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Bibliography

http%&&en.wi'ipedia.org&gps

http%&&www.bing.com&search(q)gpsPT*+)0+y)0+form)-*H/4+m't)enin

http%&&www.tes.co.u'&article.asp(storycode)01121!


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Thank You

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protection of power lines using global sevice