Automated bus transfer controller and synchronous in-phase relay for critical industrial processes

The techniques and methods for maintaining continuous electrical power to petroleum and chemical facilities from two or more utility feeders by an automated bus transfer logic controller relay system are discussed. The purpose of this relay system is to reduce transients, torsional forces, inrush currents, and motor stress while maintaining continuous motor operation when the primary facility transfers the motor load to an alternative source of electrical supply. The relay system performs the necessary logic for power-supply bus transfers in two directions by automatically selecting from either the fast, in-phase, or residual voltage methods. The controller continuously monitors the alternative source, the load bus, and the normal source. The economic considerations of maintaining continuity of production during power-supply interruptions using a transfer logic controller to supervise bus transfers may be significant. The engineering studies, application considerations, motor control design requirements, installation, and operation of the automated bus transfer controller for a chemical facility are discussed, and the present bus transfer methods are reviewed. The effectiveness of these methods for typical buses is discussed