Capacitor Banks are used for correcting the power factor in industrial plants with many inductive loads (i.e. motors). When using many inductive loads at the same time it will result in your power supply to phase shift and will lower the power factor on your system. Which Manitoba Hydro will charge for at a much higher rate.
In the picture attached, our Journeyman Electrician replaced the capacitor bank controller (which stopped working) and we brought the power factor up from 0.80 to 0.99