I have an interesting dilemma at work. We have never had the ability to monitor each individual feeder emanating from the substations. I recently installed a modern recloser on one circuit which allows detailed measurement of line characteristics and discovered that we have 1) a serious imbalance among the phases, and 2) a terrible power factor on this feeder - .33 on one phase, and .65 or worse on the other two. The meter that monitors the overall bus reads a combined power factor for the transformer connected to this system reports a total power factor of .96, so we've never bothered to investigate the load.
Now I'm concerned, seeing this amazing power factor value. It obviously doesn't affect our system, since the cumulative value is excellent at .96. But what is this doing to our customers? This circuit serves two major customer groups - a residential development on about 300 homes, and a large farming area with a bunch of wells and irrigation pumps. We've had no power quality complaints, nor any record of pump failures that might lead me to suspect a problem on our end.
But I'm concerned, nonetheless. What are the possible consequences of leaving the situation as it is? Keep in mind that this condition has existed for the nearly 11 years I've been with the company, with no ability on our part to "see" it, and we've experienced no customer service problems that I know of. Is this a non-problem I shouldn't be bother with, or should I be taking proactive steps to add some kVARS of capacitor banks on the feeder to correct the power factor?
Also, since the bus total metering is reporting such a great power factor, if I add capacitance to this feeder, will I screw that up?
We have had similar issues like you're having on the distribution system (4 kV) but not severely imbalanced between phases. What was done to remedy that was a set of fixed and switched capacitor banks. Fixed for light load periods because of the magnetizing kVA the transformers that were either lightly loaded or under utilized during off peak/shoulder periods.
If you are satisfied with the results that the recloser ever is operating then I would look at installing PQ node at the customer meter point and if there are distribution transformers upstream the meter point but downstream the substation transformers then another PQ node on the primary side of the bank supplying the pumps (Doing the residential will definitely be a waste as typically their power factors are 0.9 to 0.99). Leave it for a week to get a good load & voltage (also capture the neutral voltage & current profile as you already know will always provide great clues to problems) profile curve and analyze the data.
Just out of curiosity are the motors to the pumps single phase, three phase, or a combination? Also do you have the size of the largest motor in that facility? With the other two phase power factors dragging down to a value as low as 0.3 I would expect some customer complaints of stalled motors or excessive voltage dips on start up unless they have PFC capacitors or synch. condenser installed.
You already know seems like the simplest problems should have the simplest solutions but there are always a lot of variables that don't have any constraints.