26-10-2010, 06:03 PM
Line Arresters In Transmission Line
Jithin Lal K
S7 E2 RN:220
College Of Engineering, Trivandrum
2007-11 batch
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CONTENTS
1)Introduction
2)TLA Components
3)Types of TLA
4)Working of TLA
5)Arresters Location
6)Problems in Applications of TLA
7)Transverse Discharge
8)Experiments
9)Impulse Voltage Waveforms
10) Results
11)Minimum Distance
12)Conclusion
INTRODUCTION
Transmission Line Arresters (TLA)
Any arrester that is applied on the lines of a power system to reduce the risk of insulator flashover during surge events.
improve the lightning protection by eliminating the insulator flashover.
Need of TLA
to reduce or eliminate lightning induced outages due to flashover of insulators.
to eliminate insulator flashover due to switching surges.
Installation
lightning activity is strong
High grounding resistances of towers
TLA COMPONENTS
Saddle Clamp
connect the conductor to the insulators.
Flex Joint
eliminates mechanical stress on the arrester.
Shunt
eliminates the need of the flex joint to also be a current carrying component.
Arrester Body
electrically specified to conduct for either lightning only or for lightning and switching surges.
Disconnector
separates only in the event of an arrester failure.
Ground Lead
The ground lead connects the arrester to the tower ground.
TYPES OF TLA
Fixed Gap TLA
Also called integrated gap
the arrester unit and the series gap are assembled into a whole body.
Two ring shaped discharging electrodes.
Merits
distance is never influenced by external factors.
TYPES OF TLA
Separated Gap TLA
influence of different external factors on the distance between two discharging electrodes.
the discharging electrodes are manufactured as a complicated arc shape
Merits
The lightning impulse discharging voltage versus time characteristics of the line arresters with separated gaps are 15% higher than those of the line surge arresters with fixed gaps.
WORKING OF TLA
Lighting Strikes to
Transmission Line
Surge Over Voltage
No line Arresters
Flashover
Power Arc
Earth Fault
WORKING OF TLA
Lighting Strike to
Transmission Line
Surge Over Voltage
Line Arresters
Series Gap Sparks
Surge Diverted
Power Arc Interrupted
(with in ½ cycle)
No Service Interruption
PROBLEMS IN APPLICATION
TLA have been applied to transmission line for a decade
Line arresters were installed but the lightning failures did not decrease.
Insulator strings have not been protected by the line arresters installed.
Failure were caused by the incorrect installations of line arresters.
TRANSVERSE DISCHARGE
distance between the suspension locations of arrester and insulator = 1.0 m.
arrester unit = 1.0 m
series gap between two discharging rings = 0.56 m
total length of the 110-kV line arrester = 1.5 m
insulator string =1.1m
line arrester is placed in an inclined way
the discharging ring’s diameter= 0.245m
A-B = 0.6m
A-C < 0.8m
TRANSVERSE DISCHARGE
A-B/A-C treated as arc conductor gap
Discharging and Grading ring creates distorted magnetic field
Leads to ‘transverse discharge’ phenomenon
Small distance b/w TLA and insulator
Discharge – AB gap
Decrease in Lighting impulse flashover voltage
due to a)proximity effect
b)polluted insulator string
lightning strikes the tower
flashover A B C
lightning strikes the phase conductor
B A & B C
TRANSVERSE DISCHARGE
A-B/A-C treated as arc conductor gap
Discharging and Grading ring creates distorted magnetic field
Leads to ‘transverse discharge’ phenomenon
Very small distance b/w TLA and insulator
lightning strikes the tower
flashover C A B
lightning strikes the phase conductor
B A C
EXPERIMENTS
to analyze the influence of the distance on protection
to find out the minimum distance
thickness of the platform = 550mm
The impulse voltage +/- 2400kV lightning
Generator impulse voltage
The applied lightning impulse voltage waveform is 1.2/50 microsec.
Digital Recording System
Starting- minimum distance =1.8m
MINIMUM DISTANCE
The minimum horizontal distance between the discharging ring and the grading ring is………
0.8 m for 110-kV line
1.3 m for 220-kV line.
CONCLUSION
Improve power system reliability
Provides better protection
Maximum protection is obtained by connecting TLA parallel with insulator with minimum distance
It continues to be the area of most activity in the high voltage arrester industry
REFERENCES
[1] Jinliang He, Jun Hu, Yonghua Chen, Shuiming Chen and
Rong Zeng, “Minimum Distance of Lightning Protection Between
Insulator String and Line Surge Arrester in Parallel,” IEEE Trans. Power Del., vol. 24, no. 2, pp. 656-663, Apr. 2009
2] J. L. He, J. Hu, S. M. Chen, and R. Zeng, “Influence of series-gap structures
on lightning impulse characteristics of 110-kV line metal-oxide
surge arresters,” IEEE Trans. Power Del., vol. 23, no. 2, pp. 703–709,
Apr. 2008.
3] J. L. He, S. M. Chen, R. Zeng, J. Hu, and C. G. Deng, “Development of
polymeric surge ZnO arresters for 500-kV compact transmission line,”
IEEE Trans. Power Del., vol. 21, no. 1, pp. 113–120, Jan. 2006.
