When a critical circuit has had its operation disrupted by disturbances on the distribution system serving it, the problem can sometimes be solved by use of a dedicated circuit originating as near to the service entrance as practicable. Power specialists and representatives of the utility supplying power should be consulted when such problems are suspected.
Disturbances of this sort (voltage drops when motors are started, waveform distortions caused by the use of solid state devices and switching transients) arise within the plant and are most severe near the point where they originate. The dedicated circuit starts at (or near) a place in the system where the supply is reasonably pure. Additional filtering on the dedicated circuit can provide additional improvement when the severity of distortions makes it desirable.
The dedicated circuit does not protect a critical load from power outages except for the protection afforded by good coordination of the overcurrent devices throughout the system. Outages due to short circuits or overloads inside the plant rarely reach to the service entrance. The dedicated circuit, being supplied from a point that is nearly free of outages, will have a high degree of reliability. It will be shut down by a fault on its own conductors.
A dedicated circuit is simple to manage and is relatively inexpensive when compared to other, more elaborate systems for curing the ills of disturbances on the electrical power distribution system. There will be situations when the system is so much subject to disturbances to a point that one of the more elaborate systems will be required, but the dedicated circuit should be looked at carefully as a possible solution.
"UPS" Systems
AC Line Conditioners
Uninterruptible Power Supplies
