Electrostatic Shaft Voltage on Steam-Turbine Rotors

Abstract

Several different types of shaft voltages can be present on steam-turbine rotors. The one type that has gained increased significance in the past five years is the direct-current or electrostatic voltage. Prior to this period, electrostatic shaft voltage had not been a problem. This voltage has been causing damage to different turbine parts and, without warning to turbine operators, has been responsible for a number of serious turbine outages. The investigation which was undertaken by the authors was the result of a number of unexplainable bearing failures. The investigation showed that the cause of these failures was due to a static voltage generated in the steam turbine. The solution to the problem is to ground the turbine shaft. This has eliminated the turbine shutdowns caused by bearing failures resulting from electrostatic voltage.