Problems in overhead transmission line
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Transcript of Problems in overhead transmission line
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PROBLEMS INOVERHEAD TRANSMISSION LINE
&CONDITION MONITORING
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OUTLINES INTRODUCTION CAUSES OF DETERIORATION IDENTIFICATION OF PROBLEM SYMPTOMS TECHNIQUES FOR INSPECTION OF LINES NOVEL CONDITION MONITORING CONCLUSION
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INTRODUCTIONPOWER CAN BE TRANSMITTED AND DISTRIBUTED IN TWO WAYS
1. OVER HEAD SYSTEM 2. UNDER GROUND CABLE
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CAUSES OF DETERIORATION IN TRANSMISSION LINES
• The main problems that have been considered are:
1)Damage to insulators2)Conductor corrosion3)Vibration damage 4)Arcing damage of conductors
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DAMAGE TO INSULATORS
All insulators comes to the end of its working life either when it fails mechanically, flashes over at unacceptable high frequencies or gives evidence of deterioration to condition likely to low factor of safety in service . Insulators are mainly damaged by a) Thermal cycling b) Cement growth c) Corrosion
High-voltage insulators
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Thermal cycling
the process of cooling and heating is called thermal cycling
crack occurs moisture and water enters so insulation fails
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Cement Growth volume
expansion
radial cracks
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Corrosion
Atmospheric contaminants
Internal corrosion
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CONDUCTOR CORROSION
corrosion of alluminium strands which causes strand breakage and line failure
corrosion of galvanising
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VIBRATION DAMAGE
Aeoline vibration
Galloping
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Sub-conductor oscillation
fatigue occurs
Causes fretting between alluminium conductor near to clamps and other fitting
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ARCING DAMAGE OF CONDUCTOR
Galloping can be avoided by making the conductor circular.
But it will not work when there formation of sleet or ice coating.
If galloping occurs then flash over takes place
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IDENTIFICATION OF PROBLEM SYMPTOMS
The symptoms associated with each problem on overhead transmissions lines is predicted by:
1. Transmission line corona 2. Gap discharges
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TRANSMISSION LINE CORONA
visual corona breakdown strength The high frequency radiation
caused by corona discharges on the transmission line form a basis for assessment of corona effect.
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GAP DISCHARGES
Sparking is the easiest symptom that can be detected by radio noise measurement.
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TECHNIQUES OF INSPECTION OF LINES
The technique of overhead line inspections is done by using sensing system. All these sensing systems have focused on:
1) Partial discharging levels 2) Temperature
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NOVEL CONDITION MONITORING
TECHNIQUE
For identification of defective equipment under service conditions i.e. through online processing for monitoring the health of equipment commonly known as condition monitoring (CM).
•
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LAYOUT OF CONDITION MONITORING EQUIPMENT
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CONCLUSION The run inspection of overhead lines. The failure of insulators and conductor led to the new technique of monitoring.Replacement of the damage equipment is done very easily.
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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