3 phase voltage fluctuations with current spikes

[Master_Krafter]

Underground?

It is ungrounded from a pole transformer about 50’ away.

 

[Master_Krafter]

This video had some pointers. “There should never be voltage rise”! Saying it almost certainly a bad line side neutral somewhere.

 

[winnie]

Are you say potentially an internal neutral issu? Open or loose

Exactly. Somewhere in your system you made a set of measurements where the L-N voltage was unstable. The utility made a measurement at the transformer and claims the L-N voltage is stable. You need to keep working your way 'upstream' (toward the transformer), checking L-N voltages as your L-N load changes at each point you have access to. When the L-N voltage switches from unstable to stable, you've gone past the weak link in the neutral.

-Jonathan

 

[ptonsparky]

It is ungrounded from a pole transformer about 50’ away.

I've found many faults in underground installations. Conduit or not.