What is the monthly consumption of KWHrs and KVARHrs on your power bill? When doing a survey for a customer i request at least the last 12 month billing and prefer 24 months or more.
Are you in North America and are you penalized for a power factor of less than 0.9 or are you in a country or area where the penalty is less forgiving?
What is the nature of your load? Do you have a few large motors, lots of small motors or a mix of motors.
How many hours a day does your plant operate? How many days a week does your plant operate? Is there different loading on different shifts?
What type of plant do you have?
Do you have your own transformers?
Do you have any motors that typically run 24 hours per day?
These are all questions that I consider before applying the "Art" of power factor correction.
The science of power factor correction often costs a little more than the art of PF correction, but not as much as fully automatic correction.
After assembling the data I first ask;
How many KVARHrs per month do I need for 100% correction?
How many KVARHrs per month do I need for 90% correction?
How Many KVARs may I safely connect 24/7 and how many do I still need?
How many large motors can I correct to 100% with permanently connected capacitors and how many KVARs do I still need?
Are there any motors that run 24/7 and how much capacity may I permanently connect to them?
If there are a large number of smaller motors, I will consider correcting them in groups. A PLC may monitor the motors and connect a capacitor bank with a contactor whenever there are enough motors running to absorb the KVARs.
If the motors typically run together on a machine, I would not use a PLC but just use auxiliary contacts on the motor starters to pull in the capacitor contactor when all of the motors are running.
There are a few other tricks to the "art" of power factor correction.
The first rule of the 'Art" is do not do more than required.
If your penalty starts at 90% then correct to 90%.
If you incur a small penalty one or two months out of the year after correction, step back and look at the numbers. You may decide not to spend a few thousand dollars on added correction to save $30 or $50 a year in penalties.
If you care to provide some numbers and a description of your plant, we may make more specific suggestions.
respectfully