Eighteen 275 kV power lines have been fitted with welded rod bird guards designed to prevent damage to bird streamers. On 275 kV power lines, faults were observed on bird streamer lines on I-set, V-set and bridging assemblies.
INTRODUCTION
In this investigation, traveling wave fault locators were installed on the transmission lines to determine the location of the line faults. The bird current fault mechanism was modeled in the High Voltage Laboratory of the University of Natal.
AC AIR GAP BREAKDOWN IN SMALL AIR GAPS
Waters (Waters, 1968) investigated measurements of the electric field at the ground plane under propagation of streamers in the air gap. Noteworthy is the fact that the space charge generated in the air gap is essentially generated before the electron avalanche (once the electron avalanche has reached its critical size).
STATISTICAL ANALYSIS OF GEORGEDALE- VENUS PERFORMANCE
Discussion of fault correlation
However, there is no clear connection between the line errors and the different weather parameters. It is equally difficult to correlate line errors with bird activity because nocturnal bird habits (regarding bird interactions with power lines) are largely unknown. During the summer, spring and autumn months, most faults occur south of Griffins Hill.
This chapter attempted to identify a specific trend in bug counts and weather parameters as an indicator of a bird transmission bug mechanism. However, it has been determined that there is no apparent correlation between this failure mechanism and weather parameters. What is of interest is that during dry periods of the year line defects do not decrease; in certain cases they even increase.
This report suggests that further work needs to be done to develop time-of-day analysis as a conclusive tool in determining the causes of line errors.
DIVERGING FIELD AIR GAPS
Conclusion and discussion of results
The primary gap resistance results clearly illustrate that silicone composite insulators perform better than glass insulator assemblies under bird streamer penetration, i.e. that the streamer must penetrate closer to the line hardware to result in a flashover. Comparing the actual primary gap lengths of glass and silicone composite insulator units, and also considering the V and I insulator configurations, it is clear that if the primary gap length is greater than 410mm, it will be large enough to prevent The length of the primary gap must be increased to accommodate the practicalities of transmission tower live hardware (eg some lines may be equipped with coronaries in a horizontal plane) and the practicalities of bird droppings.
The exact trajectory of an avian streamer after shedding is not known and was not investigated during this project. To accommodate the above factors, a safety factor of 2 was applied to the primary gap length. This thesis recommends that the bird streamers be moved at least 820 mm away from the live hardware for a 275 kV system operating voltage (at STP).
Consequently, the critical distance that a bird current must be moved on a 275 kV line will be 1000 mm from the tower center (the sum of 820 mm and 180 mm).
ELECTRIC FIELD MEASUREMENTS AT THE GROUND PLANE
A capacitive probe can be used to measure the electric field at the ground plane under the penetration of bird streamers. E, = Q/Aso equation 8 The electric field in the plane can be measured by determining the charge induced on the surface. The total charge in the air gap comes not only from the electric field in the air gap, but also from the conduction current (caused by streamer activity in the air gap, equation 11).
It is important to quantify the effect of conduction current on the accuracy of the electric field measurement. It has been well documented that streamers propagate into the air gap when the electric field is greater than 4 kV/cm (Hutzler, 1978). If the electric field on the ground plate were close to 4 kV/cm, the bird harnesses would have to be moved further away from the high voltage power line hardware.
The applied voltage was increased manually and electric field measurements were recorded at specific applied voltage magnitudes.
BIRD GUARD PROJECT IMPLEMENTATION
Identification of suitable bird guards and test sites
During the months of May, June and July 1996, Line 1 experienced seven and Line 2 experienced five bird streamer failures. This was the area where most of the material for the birdwatching video was shot. Because most of the failures occurred in the middle phase, bird protection was only applied to the middle phase.
Any faults that occurred on these transmission lines were investigated using Hathaway's traveling wave fault locators and correlated with bird protection performance. As shown in Figures 38 and 39, the bird guard application covers a relatively small area of the top of the tower. This design is not intended to eliminate bird activity on transmission towers nor to prevent contamination of the isolator assembly.
These diagrams also indicate possible areas where birds can still sit and still cause a fault, e.g. the bottom of the tower boat, directly above the V chord.
Summary of bird guard field tests and results
Data on the performance of the fault shut-offs clearly show that the welded rod bird guards installed on line 2 were more effective than the rotating vane bird guards installed on line 1. Most bird streamer failures occurred outside the identified bird corridors, as a result, bird guards will be installed along the entire length of the track in all future bird guard projects. Improvements in the incidence of trips appear to be a direct result of the bird guards being installed.
As a result of the above data, welded rod bird screens were installed on a further sixteen 275 kV lines in KwaZulu-Natal. All the 18 transmission lines except Georgedale-Venus 2 and Bloukrans-Danskraal 1 had welded rod bird screens installed on them in the period from May to November 1998. However, Figure 44 does show the success of the bird watch project on the Avon-Durban North 1 power line - the number of line faults has been reduced from 4 to 0 faults per year.
This investigation determined that the majority of soil defects were caused by bird flue air gap failure.
CONCLUSION
RECOMMENDATIONS FOR FURTHER WORK
All KwaZulu-Natal 275 kV Line Faults of 1996
Ingagane-Bloedrivier 4 Ingagane-Danskraal 1 Bloukrans-Tugela 3 Bloukrans-Danskraal 1 Bloukrans-Tugela 3 Bloukrans-Tugela 3 Georgedale-Venus 2. Georgedale-Venus 1 Georgedale-Venus 1 Georgedale-Venus 1 Georgedale-Venus 1 Georgedale-Venus 1 Georgedale-Venus -Venus 1 -Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Avon-Durban Noord 1 Georgedale-Venus 2 Avon-Mersey 2 Bloukrems-Tugela 3 Georgedale-Venus 1 Georgedale-Venus 2 Georgedale-Venus 2 Avon-Durban Noord 1 Georgedale-Venus Venus -Venus 1. Wit Wit Wit Wit Wit Wit Wit Wit Wit Wit Wit Wit Wit Wit Wit Wit.
Ingagane-Danskraal 1 Georgedale-Venus 2 Georgedale-Venus 2 Klaarwater-Mersey 1 Avon-lrnpala 2 Avon-lmpala 2 Avon-Durban-Noord 1. Georgedale-Venus 1 Avon-Durban-Noord 1 Georgedale-lllovo 1 Georgedale-Venus 2 Georgedale-Venus 2 1 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-lllovo 2 Avon-Durban North 1 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Hector-Klaarwater 1 Ingagane-Danskraal 1 Avon-lmpala 2Dskraal 1Dskraal 1 Ingagane-Bloukrans 2. Drie Blou Wit Rooi Rooi Rooi Blou Rooi B-R Rooi Wit Rooi Wit Wit Wit Wit.
LPATS confirmed LPATS confirmed LPATS confirmed LPATS confirmed - 43 kA LPATS confirmed LPATS confirmed -23 kA LPATS confirmed LPATS confirmed LPATS confirmed LPATS confirmed LPATS confirmed LPATS confirmed No error. Nothing visible.
Georgedale-Venus Performance Summary 1996- 1998
Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Venus 2 Georgedale-Venus Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus Venus 2. Birds Birds Birds Birds Birds Birds Birds Birds Birds Birds Birds Birds Birds Birds Birds Birds Storm Storm Storm Storm Storm Storm Storm Storm Storm Storm Storm Unknown. White White White White White White White White White White Red White White White White White White White White White White Red Red.
Suspected Bird Streamer Faults 1993-1998
Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 1 Georgedale-Venus 1 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale- Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 1 Georgedale-Venus 1 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 1 Georgedale-Venus 1 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 1 Georgedale-Venus 1 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 1. Birds Birds Birds Unknown pollution Birds Birds Birds Birds Birds Birds Birds Birds Birds Birds Birds Birds Unknown Birds Birds Birds Pollution Unknown Pollution Birds Unknown Birds Birds Birds Unknown Pollution Birds Birds Pollution. Georgedale-Venus 1 Georgedale-Venus 2 Georgedale-Venus 1 Georgedale-Venus 2 Georgedale-Venus 1 Georgedale-Venus 2 Georgedale-Venus 1 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 1 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale- Venus 2 Georgedale-Venus 1 Georgedale-Venus 1 Georgedale-Venus 1 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 1 Georgedale-Venus 2 Georgedale-Venus 2 Georgedale-Venus 1 Georgedale-Venus 1.
Birds unknown birds birds unknown birds birds birds unknown pollution birds unknown birds pollution birds birds birds birds pollution birds birds birds birds birds.
AC Voltage Flashover Results
- Rod-plane breakdown characteristics - effects of electrode tip and rod diameter
- Effects of corona rings on breakdown characteristics 275 kV silicone composite insulator, I string with corona ring
- Effect of electrode position on air gap breakdown, using a V string silicone composite insulator assembly with corona rings
- Effect of electrode position on air gap breakdown, using glass I string, with 16 U120 BS insulator assembly
- Effect of electrode position on air gap breakdown, using an I string silicone composite insulator assembly with corona rings
- Effect of electrode position on air gap breakdown, using a V string glass insulator assembly with 16 discs per string
- Effect of wet string resistivity on air gap breakdown, using a V string glass insulator assembly
- Effects of wet string electrode on air gap breakdown, using a V string glass assembly
- Effects of wet string electrode on air gap breakdown, using a V string silicone composite insulator assembly with corona rings
- Effects of wet string electrode on air gap breakdown, using an I string silicone composite insulator assembly with corona ring
- Effect of wet string electrode on air gap breakdown, using an I string glass insulator assembly
Effect of Electrode Position on Air Gap Breakdown Using a V-Thread Silicon Composite Insulator Assembly with Corona Rings Composite Insulator Assembly with Corona Rings. Effect of Electrode Position on Air Gap Breakdown, Using I Glass Fiber, with 16U120 BS Insulator Assembly, U120 BS Insulator Assembly. Effect of Electrode Position on Air Gap Breakdown Using an I-Thread Silicon Composite Insulator Assembly with Corona Rings Composite Insulator Assembly with Corona Rings.
Effect of Wet String Resistance on Air Gap Breakdown Using a V Wire Insulator Assembly Wet String Electrode Effects on Air Gap Breakdown Using a Silicon Composite Insulator Assembly with V-thread with corona rings, composite insulator assembly with corona rings. Effects of Wet String Electrode on Air Gap Breakdown Using an I-Thread Silicon Composite Insulator Assembly Corona Ring to Corona Ring Composite Insulator Assembly.
Effect of Wet String Electrode on Air Gap Breakdown Using a Glass Fiber Insulator Assembly.
BIRD STREAMERS
IMPACT QUALITY OF SUPPLY
What is a Bird Streamer and how does it cause Line Faults?
