ballpark lights vibration

[stjohnbarleycorn]

I was asked to look at the little league ballpark.
its twelve lights, each about 7 amps , metal halide.

I am getting 85 amps back at the panel. But I am also getting a lot of vibration back at the panel that originates at the control box on the pole.
The problem is at some point the main 200 amp main trips very irregularly.
The draw on the main is about 115 amp , the circuit that has the problem is 2/0 aluminum, with a 125 amp breaker on it.
The distance is about 150 feet. I am using a true rms meter, a fluke.

I was wondering if anyone had any experience with this possibly harmonics? I will go back and check the capacitors and transformers for any problems.
I have seen this type of vibration with inductance in panels before. thanks for any help . kevin

 

[Cow]

Could there be a wire that's shorted and is having a hard time clearing? I've heard wires/breakers buzz before tripping. I'd meg the circuit first.

 

[stjohnbarleycorn]

that is very possible, one set of wires were shorted out underground already along the same line of sight. I can check that out also. thanks.