mpparent;
Did you check the voltage inputs to the static switch? Are they an A / B input from two seperate UPS systems or are they a UPS / utility fed. it sounds like you were on sub "A" one time and sub " B" on the other. Also, what type of meter are you using. The PDU...
KBA,
Have you reviewed the use of cross current compensation CT's. The output of these devices will feed directly into the AVRs. This will help in regulating the droop and voltage outputs of the machines, thus reducing the circulating currents.