We recently hooked up a power meter to a 480v substation feeding several MCC line up with VFD's. I'm seeing TDH voltage in the 3 to 4 % and current @ 30%. I thought below 10% was "not to worry" and anything above 10% could cause you problems down the road. Looks like the main contributors are the 5th, 7th harmonics, kinda of expected given the number of VFD loads. I can't remember where I got the 10% rule. Any comments, links or thoughts on the matter would be greatly appreciated.
Example of the current data
1 531
2 5.3
3 2.9
4 1.8
5 154
6 0.7
7 57
8 0.4
9 1.0
10 0.7
11 26
Example of the current data
1 531
2 5.3
3 2.9
4 1.8
5 154
6 0.7
7 57
8 0.4
9 1.0
10 0.7
11 26