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Power System Protection

Using Global Positioning

System

A Seminar reportsubmitted in partial fulfillment of

the requirements for theDegree of Bachelor of Technology

Under Biju Patnaik University of Technology

by

OM PRAKASH

(Reg. N0.-0601222200)

(2009 2010)

INSTITUTE OF ADVANCED COMPUTER AND RESEARCHPrajukti Vihar, Aurobindo marg, Rayagada -765002(Orissa).

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CERTIFICATE

This is to certify that Mr. OM PRAKASH is a final year / 7th

semester B.Tech student of Electrical & Electronics Engineering

bearing university registration number 0601222200 has been found

satisfactory in the continuous internal evaluation of technical Seminar

entitled Power System Protection Using Global Positioning System

for the requirement of B. Tech. Programme in Electrical & Electronics

Engineering underBiju Patnaik University of Technology, Rourkela,

Orissa for the academic year 2008-2009.

Date: Signature of the

Seminar

coordinator

Date: HOD

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ACKNOWLEDGEMENT

It is my proud privilege to epitomize my deepest sense of gratitude and

indebtedness to the seminar coordinator, Mr. B. Rajanarayan Prusty for his

valuable guidance, keen and sustained interest, intuitive ideas and persistent endeavor.

His inspiring assistance, laconic reciprocation and affectionate care enabled me to

complete my work smoothly and successfully.

I express my gratitude to Mr. Padarobindo Panda, H.O.D., Electrical &

Electronics Engineering for giving me the opportunity and creating a nice work

environment for me to complete my technical seminar report within the stipulated

period of time.

I acknowledge with immense pleasure the sustained interest, encouraging

attitude and constant inspiration rendered by Prof. P. Dinakar, Principal. His

continued drive for better quality in everything that happens at IACR and selfless

inspiration has always helped us to move ahead.

At the nib but not neap tide, I bow my head in gratitude at the omnipresent

Almighty for all his kindness. I still seek his blessings to proceed further.

OM PRAKASH

(0601222200)

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ABSTRACT

Turbine

This is a new technique for the protection of transmission systems by using the

global positioning system (GPS) and fault generated transients. In this scheme the

relay contains a fault transient detection system together with a communication unit,

which is connected to the power line through the high voltage coupling capacitors of

the CVT. Relays are installed at each bus bar in a transmission network. These detectthe fault generated high frequency voltage transient signals and record the time

instant corresponding to when the initial traveling wave generated by the fault arrives

at the busbar.

The decision to trip is based on the components as they propagate through the

system. extensive simulation studies of the technique were carried out to examine the

response to different power system and fault condition. The communication unit is

used to transmit and receive coded digital signals of the local information to and from

associated relays in the system.

At each substation relay determine the location of the fault by comparing the

GPS time stay measured locally with those received from the adjacent substations,

extensive simulation studies presented here demonstrate feasibility of the scheme.

OM PRAKASH (0601222200)

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Protection Of Transmission Line Using GPS

INDEX

1 .ABSTRACT

2 INTRODUCTION

3 TRANSMISSION SYSTEM

4. PROTECTION OF TRANSMISSION SYSTEM

5 TRAVELING WAVE FAULT LOCATION

6 BENEFITS OF TRAVELING WAVE FAULT LOCATION

7 TRAVELING WAVE FAULT LOCATION THEORY

8. POSSIBLE CAUSES OF FAULT

9. WHAT IS GPS?

10. HOW IT WORKS?

11. THE GPS SATELLITE SYSTEM

12. IMPLEMENTATION AND TESTING

13. WHATS THE SIGNAL?

14. HOW ACCURATE IS GPS?

15. SOURCES OF GPS SIGNAL ERRORS

16. CONCLUSION

17. REFERENCES

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INTRODUCTION

Accurate location of faults on power transmission systems can save time and

resources for the electric utility industry. Line searches for faults are costly and can be

inconclusive. Accurate information needs to be acquired quickly in a form most

useful to the power system operator communicating to field personnel.

To achieve this accuracy, a complete system of fault location technology,

hardware, communications, and software systems can be designed. Technology is

available which can help determine fault location to within a transmission span of 300

meters. Reliable self monitoring hardware can be configured for installation sites with

varying geographic and environmental conditions. Communications systems can

retrieve fault location information from substations and quickly provide that

information to system operators. Other communication systems, such as Supervisory

Control and Data Acquisition (SCADA), operate fault sectionalizing circuit breakers

and switches remotely and provide a means of fast restoration. Data from SCADA,

such as sequence of events, relays, and oscillographs, can be used for fault location

selection and verification. Software in a central computer can collect fault information

and reduce operator response time by providing only the concise information required

for field personnel communications. Fault location systems usually determine

distance to fault from a transmission line end. Field personnel can use this data to

find fault locations from transmission line maps and drawings. Some utilities have

automated this process by placing the information in a fault location Geographical

Information System (GIS) computer. Since adding transmission line data to the

computer can be a large effort, some utilities have further shortened the process by

utilizing a transmission structures location database. Several utilities have recently

created these databases for transmission inventory using GPS location

technology and handheld computers.

The inventory database probably contains more information than needed for a

fault location system, and a reduced version would save the large data-collection

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effort. Using this data, the power system operator could provide field personnel direct

location information.

TRANSMISSION SYSTEM

GENERATION TRANSMISSION DISTRIBUTION

Electric power transmission, a process in the delivery of electricity to

consumers, is the bulk transfer of electrical power. Typically, power transmission is

between the power plant and a substation near a populated area.Electricity distribution

is the delivery from the substation to the consumers.Electric power transmission

allows distant energy sources (such as hydroelectric power plants) to be connected to

consumers in population centers, and may allow exploitation of low-grade fuel

resources that would otherwise be too costly to transport to generating facilities. Due

to the large amount of power involved, transmission normally takes place at high

voltage (110 kV or above). Electricity is usually transmitted over long distance

through overhead power transmission lines. Underground power transmission is used

only in densely populated areas due to its high cost of installation and maintenance,

and because the high reactive power produces large charging currents and difficultiesin voltage management.A power transmission system is sometimes referred to

colloquially as a "grid"; however, for reasons of economy, the network is not a

mathematical grid.Redundant paths and lines are provided so that power can be routed

from any power plant to any load center, through a variety of routes, based on the

economics of the transmission path and the cost of power. Much analysis is done by

transmission companies to determine the maximum reliable capacity of each line,

which, due to system stability considerations, may be less than the physical or thermal

limit of the line.

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TRANSMISSION LINE PROTECTION

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WHAT IS TRAVELING WAVE FAULT

LOCATION?

Faults on the power transmission system cause transients that propagate along the

transmission line as waves. Each wave is a composite of frequencies, ranging from a

few kilohertz to several megahertz, having a fast rising front and a slower decaying

tail. Composite waves have a propagation velocity and characteristic impedance andtravel near the speed of light away from the fault location toward line ends. They

continue to travel throughout the power system until they diminish due to impedance

and reflection waves and a new power system equilibrium is reached. The location of

faults is accomplished by precisely time-tagging wave fronts as they cross a known

point typically in substations at line ends. With waves time tagged to sub microsecond

resolution of 30 m, fault location accuracy of 300 m can be obtained. Fault location

can then be obtained by multiplying the wave velocity by the time difference in line

ends. This collection and calculation of time data is usually done at a master station.

Master station information polling time should be fast enough for system operator

needs.

BENEFITS OF TRAVELING WAVE FAULT

LOCATIONEarly fault locators used pulsed radar. This technique uses reflected radar energy to

determine the fault location. Radar equipment is typically mobile or located at

substations and requires manual operation. This technique is popular for location of

permanent faults on cable sections when the cable is de-energized. Impedance-based

fault locators are a popular means of transmission line fault locating. They provide

algorithm advances that correct for fault resistance and load current inaccuracies. Line

length accuracies of 5% are typical for single-ended locators and 1-2% for two-

ended locator systems. Traveling wave fault locators are becoming popular where

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higher accuracy is important. Long lines, difficult accessibility lines, high voltage

direct current (HVDC), and series-compensated lines are popular applications.

POSSIBLE CAUSES OF FAULT

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WHAT IS GPS?

The Global Positioning System (GPS) is a satellite-based navigation system

made up of a network of 24 satellites placed into orbit. GPS was originally

intended for military applications, but in the 1980s, the government made the

system available for civilian use. GPS works in any weather conditions,

anywhere in the world, 24 hours a day. GPS Technology allows precise

determination of location, velocity, direction, and time. GPS are space-based

radio positioning systems that provide time and three-dimensional position

and velocity information to suitably equipped users anywhere on or near the

surface of the earth (and sometimes off the earth).Concept of satellite

navigation was first conceived after the launch of Sputnik 1 in 1957 when

scientists realized that by measuring the frequency shifts in the small bleeps

emanating from this first space vehicle it was possible to locate a point on the

earth's surface.The NAVSTAR system, operated by the US Department of

Defense, is the first such system widely available to civilian users. The

Russian system, GLONASS, is similar in operation and may prove

complimentary to the NAVSTAR system. Current GPS systems enable users

to determine their three dimensional differential position, velocity and time.By

combining GPS with current and future computer mapping techniques, we will

be better able to identify and manage our natural resources. Intelligent vehicle

location and navigation systems will let us avoid congested freeways andmore efficient routes to our destinations, saving millions of dollars in gasoline

and tons of air pollution. Travel aboard ships and aircraft will be safer in all

weather conditions. Businesses with large amounts of outside plant (railroads,

utilities) will be able to manage their resources more efficiently, reducing

consumer costs.

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HOW IT WORKS?

GPS satellites circle the earth twice a day in a very precise orbit and transmit

signal information to earth. GPS receivers take this information and use

triangulation to calculate the user's exact location. Essentially, the GPS

receiver compares the time a signal was transmitted by a satellite with the

time it was received. The time difference tells the GPS receiver how far away

the satellite is. Now, with distance measurements from a few more satellites,

the receiver can determine the user's position and display it on the unit's

electronic map. By knowing the distance from another satellite, the possible

positions of the location are narrowed down to two points (Two intersecting

circles have two points in common). A GPS receiver must be locked on to the

signal of at least three satellites to calculate a 2D position (latitude and

longitude) and track movement. With four or more satellites in view, the

receiver can determine the user's 3D position (latitude, longitude and altitude).

Once the user's position has been determined, the GPS unit can calculate

other information, such as speed, bearing, track, trip distance, distance to

destination, sunrise and sunset time and more.Accurate 3-D measurements

require four satellites. To achieve 3-D real time measurements, the receivers

need at least four channels.

CHAPTER 11

THE GPS SATELLITE SYSTEM

The 24 satellites that make up the GPS space segment are orbiting the earth

about 12,000 miles above us. They are constantly moving, making two

complete orbits in less than 24 hours. These satellites are traveling at speeds

of roughly 7,000 miles an hour. GPS satellites are powered by solar energy.

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They have backup batteries onboard to keep them running in the event of a

solar eclipse, when there's no solar power. Small rocket boosters on each

satellite keep them flying in the correct path.

Here are some other interesting facts about the GPS satellites (also called

NAVSTAR, the official U.S. Department of Defense name for GPS):

The first GPS satellite was launched in 1978.

A full constellation of 24 satellites was achieved in 1994.

Each satellite is built to last about 10 years. Replacements are

constantly being built and launched into orbit.

A GPS satellite weighs approximately 2,000 pounds and is about 17feet across with the solar panels extended.

Transmitter power is only 50 watts or less.

CHAPTER 12

IMPLEMENTATION AND TESTING

Evaluation of the fault locator involved the installation of GPS timing receivers at

four 500kV substations, see Figure 2.0. A especially developed Fault Transient

Interface Unit (FTIU) connects to the transmission lines and discriminates for a valid

traveling wave. The FTIU produces a TTL-level trigger pulse that is coincident with

the leading edge of the traveling wave. A time-tagging input function was provided

under special request to the GPS receiver manufacturer. This input accepts the TTL

level logic pulse from the FTIU and time tags the arrival of the fault-generated

traveling wave. The time tag function is accurate to within 300 nanoseconds of UTC -

well within the overall performance requirement of timing to within 1 microsecond.

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DISTORTION AND ATTENUATION

OF TRAVELING WAVES

The accuracy of fault location depends on the ability to accurately time tagging the

arrival of the traveling wave at each line terminal. The traveling wave once generated,

is subject to attenuation and distortion as it propagates along the transmission line.

Attenuation occurs due to resistive and radiated losses. Distortion of the waveform

occurs due to a variety of factors including bandwidth limitations of the transmission

line, dispersion from different propagation constants of phase-to-phase and phase-to-

ground components, etc. These effects combine to degrade the quality of the "leading

edge" of he traveling wave at large distances from the fault inception point. The

accuracy of time tagging the traveling wave diminishes for the substations far away

from the fault. Experience with the evaluation system has shown that the traveling

wave is relatively "undistorted" for distances less than 350 km. To effectively reduce

the effects of attenuation and distortion requires traveling wave detector installations

spaced at regular intervals. For B.C. Hydro, this translates to installing fault location

equipment at fourteen out of nineteen 500 kVsubstations.

Fault Locator System Test

Calculated cumulative arc length from NIC substation to the fault = 13 1,694.5

meters.

Fault Locator Difference

Output from Est. Value

Test (meters) (meters)

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Fault Locator Response to Traveling Waves Generated by Routine Switching ofSubstation Equipment

Line Estimated Tp Measured Tp

The distance to the fault fromthe line terminals is given by:

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Where Vp is the velocity of propagation for the line and

Denotes stations with travelling wavedetector installations

Figure 2.0 Fault Locator Lnstallations and Testing

HOW ACCURATE IS GPS?

Today's GPS receivers are extremely accurate, thanks to their parallel multi-channel

design. 12 parallel channel receivers are quick to lock onto satellites when first turned

on and they maintain strong locks, even in dense foliage or urban settings with tall

buildings. Certain atmospheric factors and other sources of error can affect the

accuracy of GPS receivers. GPS receivers are accurate to within 15 meters on

average. Newer GPS receivers with WAAS(Wide Area Augmentation System)

capability can improve accuracy to less than three meters on average. No additionalequipment or fees are required to take advantage of WAAS. Users can also get better

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accuracy with Differential GPS (DGPS), which corrects GPS signals to within an

average of three to five meters. The U.S. Coast Guard operates the most common

DGPS correction service. This system consists of a network of towers that receive

GPS signals and transmit a corrected signal by beacon transmitters.

CONCLUSION

Thus the use of GPS in protection of transmission systems is beneficial withrespect to

Value regarding programmatic goals:more reliable monitoring using GPSrelated technologies.

Technical merit: new fault location algorithm based on new input data.

Emphasis on transfer of technology:CCET partnership aimed atcommercialization.

Overall performance:on time, with all goals met so far.

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REFERENCES

www.wikipedia.com

www.howstuffworks.com

www.tycho.usno.org

IEEE JOURNAL

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http://www.wikipedia.com/http://www.howstuffworks.com/http://www.tycho.usno.org/http://www.wikipedia.com/http://www.howstuffworks.com/http://www.tycho.usno.org/


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