Your power monitoring system shows noticeably increased current draw on several feeders over the past few months. For example, one 1,200A breaker carried about 700A but now is carrying about 790A. Yet, no new loads have been added.
You looked at harmonics and power factor history, but no problems were found there. In fact, last spring, several large motors received new electronic drives that reduced harmonics and raised power factor. You discussed this with your boss, who also expressed being puzzled. "Well," he said, "at least we know it's not the feeder cables because we replaced a bunch of those last year." He suggests the problem is the power monitoring system is drifting. What should you look at?
It's unlikely your power monitoring system is the problem, but cross-check it with your portable power analyzer. Under the "what has changed theory," the newness of the cables makes them the most recently introduced variable. You should suspect possible cable leakage.
Cables can be damaged during installation via pulling errors or even people walking on them. Exceeding the bend radius and pulling with too much force are just two pulling errors that occur. Other errors can also cause problems. For example, are the cables the correct insulation for the application? What about ampacity?
First, verify the cables are correct for the application. Then, conduct the following tests: thermal survey, insulation resistance, and leakage.