Question auxiliary Ground Electrodes

[codequestion]

I have customer owned transformer which is grounded in the middle of field with ground rods. Next to the transformer is metal backboard on which I have panelboards to power and control site lights. My questions are:

1. Can I ground the metal backboard to the same ground rods that is used as system ground for transformer?

2. If yes then how can I size the conductor? It would not be call GEC I suppose.

 

[ActionDave]

What's important is how the transformers and panels are wired and bonded. If everything is wired properly then the metal back boards have a connection to the ground rods already. If you do add an additional wire it would be an auxiliary grounding electrode conductor and 250.54 doesn't say much except make sure they are connected to an equipment grounding conductor.