Bus Bar Bolted Connections: Reliability and Testing

Reliable bolted bus bar connections are necessary for the decades of life expected from them. This is especially true for bus bar systems in electric power stations where over 40 years life is the norm. A failure of a bolted connection can result in a substantial disruption of the power station's output and a major inconvenience to its customers. This paper discusses how best to make bolted connections between Al to Al, Al to Cu and Cu to Cu bus. The typical aging curve for a bolted joint is discussed. The advantages and disadvantages of infrared thermography and external joint temperature measurements as joint inspection tools are presented. The concept of bolted bus contact resistance is shown to be a reliable bolted joint inspection tool. It is shown that an increase of two times the original bolted joint's contact resistance is a reliable measure that a bolted connection is in the initial stages of failure. Experimental data for a poorly made bolted bus connection and well bolted busbar joints are presented to illustrate the importance of knowledge of this contact resistance increase in order to take timely corrective action. Finally, a straightforward method of regular inspection and maintenance of the bolted connection is presented.