TABLE OF CONTENTS The main connections bus bar (Fig. 14.1) connects the generator to its associated generator transformer. An aluminum tube (conductor) surrounded by a concentric enclosure of the same material is used for each phase of the generator. Since each enclosure is isolated from its neighbor, the term isolated phase bus bar (IPBB) is used.
The conductor of each phase is supported at the center of the enclosure by equispaced insulators. These insulators are rigidly fixed around the circumference of the enclosure. They allow limited radial movement of the conductor. The rating of the busbar installation is based on the temperature rise above a specified ambient at maximum load and its ability to withstand ground (earth) and three-phase short-circuit faults anywhere in the generator system without damage.
The currents flowing in the conductors produce large magnetic fields around them. These fields induce currents in the enclosures and generate forces between all the conductors and the enclosures. The extreme ends of each phase enclosure are bonded together to reduce these forces. This allows a balanced current flow in the enclosures of the three phases (Fig. 14.2). This arrangement is called electrically continuous IPBB with short-circuit.
The enclosures are supported by insulated foot mountings to insulate them from the grounds. They are also grounded at one point. The circulating currents in the enclosures are controlled by isolating them from...
