DR.BABASAHEB AMBEDKAR TECHNOLOGICAL UNIVERSITY,

LONERE-RAIGAD

A

SEMINAR PRESENTATION

ON

“EHVAC TRANSMISSION LINE MAINTENANCE

TECHNIQUES IN INDIAN PERSPECTIVE-A REVIEW”

PRESENTED BY,

Mr. YASHWANT H. CHAUDHARI

(20140203)

UNDER THE GUIDANCE OF,

PROF. ANISH SALVI

CONTENT

Introduction

overview of ehvac transmission line

maintenance in India

Methods of transmission line maintenance

Benefits of hot line maintenance techniques

Works done by live line technique

Necessity of ehv transmission line

Advantages, Disadvantages, Applications, Future Outlook.

INTRODUCTION

The major challenge in Indian power sector is operating upgrading of the

transmission & distribution lines with efficient metering.

Application of smart grid devices for consistently condition monitoring of

overhead lines &substation can decides the action of maintenance required and

thus condition-based maintenance (CBM) technique can be implemented.

To meet ever increase in demand, reduction of value of losses, utilization of huge

renewable energy and absence of automation in power Transmission &

Distribution, there is need of Preventive Maintenance (PM) & logy(RCM).

To maintain stability of power system up gradation is essential.

This Seminar shows various Transmission Lines Maintenance techniques available

and maintenance techniques presently utilized in India.

OVERVIEW OF EHVAC TRANSMISSION LINES

MAINTENANCE IN INDIA

To maintain continuity of electricity and stable supply forconsumer’s higher availability of transmission system is required.

Main reasons for failure of 30% overhead distribution lines are dueto failing of electrical equipment, e.g. cut-outs, insulators,conductors, lightning arresters, ear thing etc.

Before taking outages, equipment failure can be identified & planfor replacement of same.

Changing of failure equipment reduces reliability index.

Preventive maintenance provides Cold line Maintenance and liveline Maintenance techniques gives best results.

Methods of Transmission Line Maintenance

Predictive Maintenance :

Thermo graphic test is important maintenance programs in condition monitoring of hardware elements in substations and transmission lines.

PID Testing for insulators in substations and overhead lines.

Preventive Maintenance :

Cold Line maintenance

Live line maintenance

PREDICTIVE MAINTENANCE

Insulators tester works on the automatic

measurement and recording of the

electric field which shows reduced value

of internally-shorted insulator.

Sliding of Tester on the testing string of

insulators which automatically measures

and stored electric field information up to

200 strings.

After test it can be downloaded in a host

computer and/or in a device to be store

PID TESTER KIT :

Preventive Maintenance Cold line Maintenance :

Cold Line Maintenance Method is the method of maintenance in which supply is completely switched off (de energized the line

during the maintenance work) on which maintenance has to carried out . Planned outage are carried out by disconnection of supply to avoid

any accident or risk involved due work under high voltages.

Cold Line Maintenance can perform following Operations of EHV lines :

Line Survey, Thermography, Attending hotspot.

Punctured Insulator Detection (PID).

Insulator Replacement & Insulator Washing.

Testing – Contact Resistance Measurement.

Mid span joint replacement.

Replacement of Insulator , hardware and conductor accessories.

Jumper strengthening and replacement.

Tower extension, raising ht. of tower.

Earth Wire Replacement.

ERS – EMERGENCY RESTORATION SYSTEM.

LIVE LINE MAINTENANCE

Live line Maintenance :

Live line is the technique of maintenance of transmission lines, conductors, line insulators, substation equipment,

structural, parts etc. operating at high voltages while the Line or equipment are energized.

Supply utilities trying to maintain continuity of supply otherwise they face customer’s complaints and penalized.

To maintain the continuity of supply there is need to inspect, rectify & replacement of defective parts to avoid costly

forced outages.

. Advanced tools and technologies developed are taken into consideration. Most of maintenance works can be made

with energizing the line.

Switching cycles of switchgears can be reduced by live working and it helps to reduce the incident risks considering

the age of equipment.

BENEFITS OF HOT LINE MAINTENANCE TECHNIQUES

The stability of the grid is increases, Reduces Probability of permanent circuit

interruptions

Avoid accidents, increasing safety at work.

Live line Saves Line breakdown, eliminating interruptions to the supply, compensate

the initial investment.

Avoid revenue loss, breakdown cost & maintenance cost. This is cheaper from social

& economical point.

Requires less manpower compared to manpower for breakdown maintenance.

WORKS DONE BY LIVE LINE TECHNIQUE

Repair of conductor of overhead line or bus bars.

Repair of overhead earthling wire, while circuit is live.

Inspection, repairs & replacements of Insulators with circuit live.

Hot line washing of insulators.

Aerial numbering plates installation or replacement.

Vibration dampers replacement on live conductor and on ground wire.

Suspension clamps replacement or installation with or without armour-rod.

Changing of broken Pin-cap insulators.

Changing of insulator string straps on the cross arm and arching devices.

Work on the tower foundation.

PICTURES OF COLD AND LIVE LINE MAINTENANCE

COLD LINE MAINENANCE LIVE LINE MAINENANCE

Methods of Live Line Maintenance

A. Hot Stick Method :

In this method the lineman will be at ground potential, working with Hot Sticks (tools) keeping safe

clearance from the line.

In the electric power distribution industry, a hot stick is an insulated pole, usually made of fiberglass, used

by electric utility workers when engaged on live-line working on energized high-voltage electric power lines, to

protect them from electric shock.

Depending upon tool we can preform : test for voltage, tighten nuts and bolts, open and

close switches, replace fuse.

Hot sticks are made in different lengths, from simple 3 foot (1 m) sticks to 30 foot (9 m) telescoping

models.

Osha Standards For Safe Working

Voltage range phase to phase

in KV

Meters FEETS

46.1 - 72.5 0.91 3

72.6 – 121 1.02 3.4

138 – 145 1.07 3.6

161 – 169 1.12 3.8

230 – 242 1.52 5

345 – 362 2.13 7

500 – 552 3.35 11

.

B. Bare Hand Method :

The barehanded approach has a live line worker performing the work in direct electric contact

with live parts.

Before contact, the worker's body is raised to the same electric potential as the live parts, and

then held there by electric connection, while maintaining suitable isolation from the surroundings

which are at different potentials, like the ground, other people or trees. Because the worker and

the work are at the same potential, no current flows through the worker.

For this conductive suits made of 25% microscopic stainless steel and 75% nomex will be

provided.

C. Combination Of Hot Stick & Bare Hand Method:-

Generally a combination of above two methods is used in practice as

HSM & BHM are complimentary and supplementary to each other.

To reach on tower structures and live conductors, insulated ladders and

insulated aerial platforms are used along with helicopters.

As per maintenance requirements, available local conditions, tools

resources advance techniques have been design and developed.

.

---------------HOT STICK METHOD

BARE HAND METHOD-------------------------

NECESSITY OF EHV TRANSMISSION LINE

With the increase in transmission voltage, for same amount of power to be transmitted current in the line

decreases which reduces I^2R losses. This will lead to increase in transmission efficiency.

With decrease in transmission current, size of conductor required reduces which decreases the volume of

conductor.

The transmission capacity is proportional to square of operating voltages. Thus the transmission capacity of line

increases with increase in voltage.

With increase in level of transmission voltage, the installation cost of the transmission line per km decreases.

It is economical with EHV transmission to interconnect the power systems on a large scale.

The no. of circuits and the land requirement for transmission decreases with the use of higher transmission

voltages.

ADVANTAGES

The major advantages are:

Reduction in the current.

Reduction in the losses.

Reduction in volume of conductor material required.

Decrease in voltage drop & improvement of voltage regulation.

Increase in Transmission Efficiency.

Increased power handling capacity.

.

The no. of circuits & the land requirement reduces as transmission voltage increases.

The total line cost per MW per km decreases considerably with the increase in line voltage.

Maintenance Technology with Smart Grid (SG) technology gives features such as maintaining

stability of the system, increase in transmission capacity, improving supply quality, improvement

in overall performance etc.

Remodelling the energy scenario of the global market.

It also improves other performances such as advanced communication, protocol, advanced

management and architecture with fast data exchange

This technology has a quality to improve performance of other technologies such as Flexible AC

Transmission System (FACTS) and Wide Area Monitoring (WAM) in urban & rural area

DISADVANTAGESThe Major Disadvantage Are:

Corona Loss & Radio Interference

Line Supports

Erection Difficulties

Insulation Needs

The Cost Of Transformers, Switchgear Equipment's & Protective Equipment's Increases With Increase In

Transmission Line Voltage.

The EHV Lines Generates Electrostatic Effects Which Are Harmful To Human Beings & Animals.

Limitation For HVAC Transmission System :

Power Loss – Reactive.

Stability Limit.

Ferranti Effect.

Difficult To Control Power Flow.

APPLICATIONS

High voltage is used:

In electrical power distribution,

In cathode ray tubes, to generate X-rays and particle beams, to demonstrate arcing, for ignition, in

photomultiplier tubes, and high power amplifier vacuum tubes and

Other industrial and scientific applications.

FUTURE OUTLOOK

As per energy experts future work would be online monitoring data, intelligent maintenance using expert systems, reliability

analysis and accurate evaluation system. There is need in development of high voltage intelligent equipment's and there

residual life estimation and life cycle management system.

Renovation and Modernization of Generation Sector :

Development of National Grid.

Strengthened role of Renewable in the sector.

Implementation of modern techniques for electric power conservation (DSM).

Introducing Cogeneration Systems.

Institution of energy audit.

Adoption of innovative business models.

References

[1] 2016 International Conference on Global Trends in Signal

Processing, Information Computing and Communication” EHVAC

Transmission Lines Maintenance Techniques in Indian Perspective -

A Review”.978-1-5090-0467-6/16/$31.00 ©2016 IEEE.

[2] M. Fairer, M. Khalil, C. Lauran, G. Leone, S. Toscana, “Outage Data

Analysis and RAMS Evaluation of the Italian Overhead Transmission

Lines”, IEEE, June 2016.

[3] Gokturk Poyrazoglu, “Scheduling Maintenance for Reliable

Transmission Systems”, IEEE, pp. 1-5, April 2016.

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THANK

YOU…

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