Arrester Cantilever Strength ? 2

[wesles24]

Can someone please explain to me what cantilever strength is when talking about surge arresters (what it is, how it affects the arrester)? A link or good explanation would be appreciated.
Thanks!

 

[desertfox]

Hi wesles24

The cantilever strength is the mechanical strength of the arrester, imagine the arrester in the horizontal plane similar to a diving board at the local swimming pool and at various points along it you apply a external load, the further away from the fixed end you apply the load the larger the bending moment becomes and hence an increased mechanical stress on the device.

Hope this helps

 

[desertfox]

Page 8 of 51 of this link, page number on the PDF is D-1

http://www.cablejoints.co.uk/upload/High_Voltage_Surge_Arresters___ABB_Buyers_Guide.pdf

 

[BlownUp]

Just as desertfox has described, when mounted at one end, mechanically an arrester is a cantilevered beam. The mechanical strength of it is determined by how much torque the arrester can withstand without damage. When making attachments to the arrester it is important to verify the installation will not apply more torque than the arrester can handle. The torque can be converted to a force at the terminal point based on the length of the arrester. Keep in mind that there will be wind loading and if mounted horizontally there will be gravity loading.

One thing to be careful of with arresters is to be mindful of supporting equipment with them. Although rare if properly applied, arresters are known to break during severe electrical stress. In this case they will lose all mechanical properties. However, this failure mode may not necessarily result in a system outage. In practice we try to insure that in the event of failure any connecting cables will hang "clear" of any obstruction that would cause a fault. And we never use an arrester for supporting other equipment.

IEEE 605 has a good write up and explanation for cantilever strength of insulators. The same would apply to arresters.

 

[wesles24]

Thank you both for the reply, I understand now!