Technological innovations in deep coal mine power systems

Various innovations and changes have occurred to underground coal-mine power systems during the past ten years. Some of these are the use of higher utilization and distribution voltages and their associated switchgear; the use of programmable logic controllers for control, monitoring, and diagnostic applications; improved protective relaying with built-in test circuitry; power-factor correction near loads for improved voltage regulation; and modifications to power-system component arrangement. Many of the innovations were necessitated by significant increases in power requirements of face equipment, particularly longwall equipment, while others are the result of improved technology. In either case, improved power-system operating characteristics, as well as enhanced levels of safety, have resulted. This paper describes many of the major innovations that have evolved