Transmission Line Surge Arrester Application

[switchnlight]

Our electric utility is in Southern Africa and we have some subtransmission lines (66kV, 88kV and 132kV) that span through areas with high ligtning flash density and every rain season, we experience abnormally high line outages due to lightning coupled with porcelain insulator damage. The line outage stats for the last two years have been worrying and we have been tasked to look at ways of improving the performance of these lines. I read in some T&D journal (though the paper wasn't very detailled) that some utilities are using gapless metal oxide line surge arresters installed on towers to improve the lightning performance of transmission lines. Could forum members with more infor and experience on this kindly share it with me especially with regard to dimensioning of the line surge arresters and wether they affect the coordination of the relay protection for the lines.

 

[cuky2000]

Beware that this phenomenon is random in nature and there is not a cookbook or magic solution to this problem. The use of surge arrester may be effective but require significant investment to mitigate high failure rate in power distribution and HV lines. It is not uncommon to consider arrester in each phase and virtually at every pole to achieve significant reduction in the failure statistics.

The first step suggested is to gather and organize the failure data and perform an insulation coordination study addressing the ranking line by importance and considering shielding protection with ground wire(s), grounding system, soil resistivity, insulators dielectric ratings, BIL of tower, physical configuration, pollution levels, etc.

The enclose link provide sample of overvoltage line performance with and without surge arrested and typical line protection with MOSA that I hope you may use as starting point in your assignment.

http://cuky2000.250free.com/Surge_Arrester_Line_Performance_1.jpg

http://cuky2000.250free.com/Surge_Arrester_Line_Performance_1.jpg

Good luck.

 

[cuky2000]

Please disregard one of the duplicated links. Here is the typical application of SA for lightning protection in power lines that I intended to post above.

http://cuky2000.250free.com/Surge_Arrester_Line_Application_1.jpg

 

[mc5w]

Florida Power and Light likes to use 34.5 KV construction for 7,620Y13,200 volt lines in urban and suburban areas. Once every 3 poles and on each side of each section switch they have arrestors for all 3 phases. That is, there are some parts on the United States where it is customary to use a 250% insulation level.

I have also seen a double circuit 34.5 KV line in Parma, Ohio along Snow Road that has a lightning arrestor for the top 2 wires once every 2 poles. This Cleveland Electric Illuminating line gets about 2 to 6 exploded lightning arrestors every year.