A vital aspect of asset management on power systems is understanding the remaining life of a critical component. Predicting the life of these components while on-line or off-line is an onerous task at best. This document offers guidance when selecting the method to test surge arresters away from the lab environment. Testing surge arresters in the field is important on both transmission systems and distribution systems since they are extensively applied in both.  The various field test methods of assessing the life of arresters are reviewed.  The positive and negative attributes are discussed for all test methods.  A table that clearly contrasts the benefits of each test type based on the situation is presented.   more ...

I recently received the letter below from a power engineer.  He brings up a subject that has long been a question of mine also.   Do we really need an arrester ground conductor if the arrester is mounted directly to a grounded transformer tank or grounded structure.   Here is the total question in his words.

Mr. Woodworth:

My opinion is that a ground lead between the arrester base and the tank wall (keeping the lead length to less than a few feet) is cheap insurance and is the best "quantifiable" surge path to the tank wall. 

Admittedly, I do believe the base-to-bracket-to-tank-wall path is probably the lowest surge impedance path, provided everything is prepared correctly.  However, the copper lead between the arrester base and the ground pad is easily made and easily inspected and results in a "known quantity".