TRANSMISSION LINE

1. PROBLEMS IN
OVERHEAD TRANSMISSION LINE
&
CONDITION MONITORING

2. OUTLINES
 INTRODUCTION
 CAUSESOF DETERIORATION
 IDENTIFICATION OF PROBLEM
SYMPTOMS
 TECHNIQUESFOR INSPECTION OF
LINES
 NOVEL CONDITION MONITORING
 CONCLUSION

3. INTRODUCTION
POWER CAN BE TRANSMITTED AND
DISTRIBUTED IN TWO WAYS
1. OVER HEAD SYSTEM
2. UNDER GROUND CABLE

4. CAUSES OF DETERIORATION IN
TRANSMISSION LINES
• Themain problemsthat havebeen considered
are:
1)Damage to insulators
2)Conductor corrosion
3)Vibration damage
4)Arcing damageof conductors

5. DAMAGE TO
INSULATORS
All insulators comes to the
end of its working life
eitherwhen it fails
mechanically, flashes over
at unacceptable high
frequencies orgives
evidence of deterioration
to condition likely to low
factorof safety in
service .
Insulators are mainly
damaged by
a) Thermal
cycling
High-voltage insulators

6. Thermal cycling
 theprocessof cooling and heating iscalled
thermal cycling
 crack occurs
 moistureand water enters
 so insulation fails

7. Cement Growth
 volumeexpansion
 radial cracks

8. Corrosion
 Atmospheric contaminants
 Internal corrosion

9. CONDUCTOR
CORROSION
 corrosion of alluminium strands
which causesstrand breakageand line
failure
 corrosion of galvanising

11. VIBRATION DAMAGE
 Aeoline vibration
 Galloping

13. Sub-conductor oscillation
 fatigue occurs
 Causes fretting
between
alluminium
conductor near to
clamps and other
fitting

14. ARCING DAMAGE OF
CONDUCTOR
 Galloping can beavoided by
making the conductor
circular.
 But it will not work when
there formation of sleet or
icecoating.
 If galloping occursthen flash
over takesplace

15. IDENTIFICATION OF
PROBLEM SYMPTOMS
The symptoms associated with each
problem on overhead transmissions lines
ispredicted by:
1. Transmission linecorona
2. Gap discharges

16. TRANSMISSION LINE
CORONA
 visual corona
 breakdown strength
 The high frequency radiation caused by
corona discharges on the transmission line
form abasisfor assessment of coronaeffect.

17. GAP DISCHARGES
 Sparking is the easiest symptom that can
bedetected by radio noisemeasurement.

18. TECHNIQUES OF
INSPECTION OF LINES
 Thetechniqueof overhead line
inspectionsisdoneby using sensing
system. All thesesensing systemshave
focused on:
1) Partial discharging levels
2) Temperature

19. NOVEL CONDITION MONITORING
TECHNIQUE
 For identification of defectiveequipment
under serviceconditionsi.e. through online
processing for monitoring thehealth of
equipment commonly known ascondition
monitoring (CM).
•

20. LAYOUT OF CONDITION
MONITORING EQUIPMENT

21. CONCLUSION
Therun inspection of overhead lines.
Thefailureof insulatorsand conductor led to
thenew techniqueof monitoring.
Replacement of thedamageequipment isdone
very easily.

22. REFERENCES
1. R. Ferraro, 1990, Electric Service Compatibility: Dealing with Realities,
Power Quality Magazine
2.HUNT, J.C.R., and RICHARDS, D.J.W.: 'Overhead-line oscillations and the
effect of aerodynamic dampers', Proc.IEE 1969,116, (ll),pp. 1869-74.
3. WILTON, G.S., ORMISTON, T.S., and ALLAN,R.A.: 'Modern transmission-
line maintenance', ibid., 1967,114, (7),pp.925-932
4. Electric Power Research Institute, “Transmission Line Reference Book, Wind
Induced Conductor Motion”, Research Project 795, 1978
5. F.B. Farquharson and R.E. McHugh, “Wind Tunnel Investigation of
Conductors Vibration Using Rigid Models”, IEEE Transaction Paper,
October 1956, pp. 871-877