Large motors/small system: effective operation with voltage sag [pulp mill power quality]

An economically acceptable solution to power quality problems, including both generation and voltage sag, appeared unattainable in a Canadian pulp mill. Once given the sizes and locations of new loads, the existing electrical distribution system was studied to see if proposed loads could be added to the system. It was apparent immediately that this was not possible. The power system was an island system, not connected to the utility network. Power generation could not be increased. Full voltage starting of the new, large motors would cause excessive voltage sag no matter what the power source. Further, the existing system was operating near or above rating in several critical areas. The authors describe how the solution became a classic application of IEEE Red Book Section 2.5, which covers power system modernization and evaluation programs. Considerations of safety, operations and maintenance played a major part in every design decision.