PROTECTION OF POWER TRANSMISSION LINES

EMBEDED CONCEPTS

INTRODUCTION TRANSMISSION SYSTEM FAULT CONDITION TRAVELLING WAVE FAULT THEORY FAULT LOCATION USING GPS ADVANTAGES AND DISADVANTAGES CONCLUSION

INTRODUCTION

New Techniques for the protection of transmission lines .

Relays are installed at each bus bar in a transmission network.

Relay contains a fault detection system together with a GPS communication system.

GPS determine the location of the fault. GPS Technique

TRANSMISSION SYSTEM

TRANSMISSIONGENERATION DISTRIBUTION

A Fault is an abnormal flow of currents

Possible fault conditions :

Lightening strikes near lineSnow storms/icing on lines causes to sag High winds Bird or animal contactConductor clash

LOCATION OF FAULT Helps to…

Save time and resources for electric utility industry

Determine “distance to fault “from a transmission line end

Aid in fast restoration of power Communication systems can retrieve

fault location system

What is travelling wave fault location ? Faults on the power transmission

systems causes transients that propagate along transmission lines as waves .

These waves have a propagation velocity and characteristic impedance ,travel from fault location towards line ends.

The location of faults is accomplished by precisely time-tagging wave fronts as they cross a known point typically in substations at line ends .

Fault location can be obtained by multiplying the wave velocity by the time difference in line ends .

TRAVELLING WAVE FAULT LOCATION THEORYTravelling wave fault locators make use of

transient signals generated by the fault.Unlike other fault location systems ,the

travelling wave fault locator is unaffected by load conditions

Precisely synchronized clocks are the key element in the implementation of this fault location techniques

The required level of clock accuracy has only recently been available at reasonable cost with the introduction of GPS

BENEFITS OF TRAVELLING WAVE LOCATION THEORYEarly fault locators used RADAR RADAR equipment is typically mobile are

located at substations and requires manual operation

Travelling wave fault locators are becoming popular where higher accuracy is important

GPS-based sub microsecond timing system has proven reliable in several utility travelling wave projects

FAULT LOCATION USING GPSGlobal positioning system(GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit.

Originally intended for military applications

Allows precise determination of location, velocity , direction and time

HOW GPS WORKS ?GPS satellite circle the earth twice a day.Transmit signal information to Earth.Receiver take this information and calculate

the user’s exact location.Accurate 3D location requires 4 satellitesGPS satellite transmits two low power radio

signals

Operation of the fault location system (FLS) using GPSA fault locator remote is

coupled to each end of the line via CPT

FL is synchronized to the common timing standard of UTC from GPS

Fault resulting produces travelling waves (transients)

The FL remote time tag the transient arrival times

By knowing the line length(L) and time of arrival difference (tb-ta) distance X can be calculated from the FL equation

X=[L-C(tb-ta)]/2

ta & tb are end A and end B arrival time

C=velocity of light

ADVANTAGESProtection of transmission line using GPS is

extremely accurate.Economical Fast response Reliability and availability

DISADVANTAGESSignal multipath Receiver clock errors Number of satellites visible

Ionosphere and troposphere delays

CONCLUSIONUses a dedicated fault detector to extract

transient signal and GPS system to time tag the signals .

Travelling time of the transient signal from the point of the fault to the adjacent substation is used to determine the fault location

Proposed technique is able to offer a high accuracy in fault location

Unlike traditional protection schemes this technique offers a new concept in network protection