analysis of outages of eht transmission lines and

8/9/2019 Analysis of Outages of EHT Transmission Lines And

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Analysis of outages of EHT transmission lines andAnalysis of outages of EHT transmission lines andcomputation of Availability factor ofcomputation of Availability factor of

transmission systemtransmission system


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CONTENTSCONTENTS

Abstract

Introduction

Components of transmission system

Transmission line design

HVDC versus HVAC

Factors that causes outages

Analysis of outages of EHT transmission line

during ground fault


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ABSTRACTABSTRACT

y Electricity is generated as it is used. Unlike other commodities,

there is very little ability to store electricity.

y The amount of power on a transmission line at any given moment

depends on generation production and dispatch, customer use, the

status of other transmission lines and their associated equipment,

and even the weather.

y In this we are going to study about the transmission system,

components of transmission system and the outages of the EHT

transmission line.

y One of the important things is to compute the availability factor oftransmission system.


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INTRODUCTIONINTRODUCTION

In transmission system transmission lines functions as arteries that carry

electricity from power stations to regions where the power is needed.

It is vital to control construction and maintenance coasts of these lines.

The electrical transmission system is more complex and dynamic than

other utility systems, such as water or natural gas.

The electric system is highly interconnected.

The electricity from many power plants is pooled in the transmission

system, and each distribution system draws from this pool.


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Components of the transmission system


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Transmission line designTransmission line design

y The electric lines that generate the

most public interest are high

voltage transmission lines.

y Transmission line poles or

structures are between 60 and 140feet tall. Distribution line structures

are approximately 40 feet tall.

y Current right-of-way widths vary

between 80 to 140 feet.

y

Transmission structures1. Single circuit davit

2. Double circuit davit

3. H-frame

4. Horizontal line post


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What is an EHT transmission line?

It is an coaxial transmission line allows the inner

conductor of our new EHT transmission line to run

cooler than standard line at the same input power.

The average power ratings of this new line are up to

45% higher than standard coaxial line.

Advantages:

Enhanced Power Handling

Lower Tower Wind loading

Proven Connector and Inner Support Designs

Available in All Line Sizes and Types


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HVDC versus HVAC:HVDC versus HVAC: A HVDC transmission line costs less than an AC line for

the same transmission capacity.

In a long AC cable transmission, the reactive power flow

due to the large cable capacitance will limit the maximum

transmission distance. With HVDC there is no such limitation.

In contrast, loss levels increase with distance in a high

voltage AC system.

An optimized HVDC transmission line has lower losses thanAC lines for the same power capacity.

It is sometimes difficult or impossible to connect two AC

networks due to stability reasons. In such cases HVDC is the

only way to make an exchange of power between the two

networks possible.

One of the fundamental advantages with HVDC is that it is veryeasy to control the active power in the link.

Limit short circuit currents. Improved energy transmission

possibilities contribute to a more efficient utilization of existing

power plants.


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Factors that causes outagesFactors that causes outages

y Planned outages (lack of adequate planning).

y

Weather problems.y Shortage of man power.

y Due to the damage of electrical equipment.

y Poor financing.

y Negligence of power holding company staff

and institutional staff.

y Problem of load shedding.

Faults in power system:

y Shunt faults (Short Ckt Type):

(a) Symmetrical faults:

1. L-L fault, 2.L-G fault, 3. L-L-G fault(b) Un symmetrical faults:

1. 3 Phase faults

y Series faults (Open Conductor Type) :

1.One open conductor

2.Two open conductor


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ANALYSIS OFOUTAGES OF EHT TRANSMISSION LINEANALYSIS OFOUTAGES OF EHT TRANSMISSION LINEDURING GROUNDFAULTDURING GROUNDFAULT

When a ground fault occurs on an overhead transmission line in a power

network with grounded neutral, the fault current returns to the grounded

neutral through the tower structure ground return path and ground wires.

Applying continuous fractions theory, the expression for the equivalent

impedance seen from the fault location will beZ = Zcpd / 2 + ((Zcpd Zst) + (Zcpd2 / 4))

For an infinite line in both directions

1 / Z

= 1 / Z

+ 1 / Zst + 1 / ZZ= 1 / (2 / Z+ 1 / Zst)


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The voltage rise of the faulted tower V0 is given by the next expression

V0 = (1-v) Id Z


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RESULT:RESULT:


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QUERIES

?


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THANK YOU

analysis of outages of eht transmission lines and

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