problems in overhead transmission line

PROBLEMS INOVERHEAD TRANSMISSION LINE

&CONDITION MONITORING

OUTLINES INTRODUCTION CAUSES OF DETERIORATION IDENTIFICATION OF PROBLEM SYMPTOMS TECHNIQUES FOR INSPECTION OF LINES NOVEL CONDITION MONITORING CONCLUSION

INTRODUCTIONPOWER CAN BE TRANSMITTED AND DISTRIBUTED IN TWO WAYS

1. OVER HEAD SYSTEM 2. UNDER GROUND CABLE

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

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

Thermal cycling

the process of cooling and heating is called thermal cycling

crack occurs moisture and water enters so insulation fails

Cement Growth volume

expansion

radial cracks

Corrosion

Atmospheric contaminants

Internal corrosion

CONDUCTOR CORROSION

corrosion of alluminium strands which causes strand breakage and line failure

corrosion of galvanising

VIBRATION DAMAGE

Aeoline vibration

Galloping

Sub-conductor oscillation

fatigue occurs

Causes fretting between alluminium conductor near to clamps and other fitting

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

IDENTIFICATION OF PROBLEM SYMPTOMS

The symptoms associated with each problem on overhead transmissions lines is predicted by:

1. Transmission line corona 2. Gap discharges

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.

GAP DISCHARGES

Sparking is the easiest symptom that can be detected by radio noise measurement.

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

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).

•

LAYOUT OF CONDITION MONITORING EQUIPMENT

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.

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