IEEE Std 2740-2020 pdf download – IEEE Guide for Selection and Installation of Electrical Cables and Cable Systems in Hazardous (Classified) Locations on Oil and Gas Land Drilling Rigs.
8. AC and DC top drive power service loops An ac or dc top drive power service loop is either a special type of umbilical or drag chain assembly that operates in a rigorous and physically abusive environment and yet fits into a very limited envelope of space. The power service loop connects between the top drive and the derrick and hangs freely in the air between these two mounting points in a pronounced U-shaped catenary configuration. It feeds electrical power to the top drive drill motor as the top drive is hoisted up and lowered down along a track in the derrick during drilling operations. The uniqueness of the application, due to the environment on a drilling rig that the power service loop operates in, dictates that special considerations shall be made relative to its mechanical and electrical design criteria. The power service loop cable size shall have a continuous current-carrying capacity determined by multiplying the 0.80 duty factor times the continuous current rating of the top drive drill motor. The power service loop cable size shall be selected such that the cable temperature does not exceed the emergency overload temperature rating of the cable (reference ANSI/NEMA WC 70/ICEA S-95-658, Appendix C; interpolation between published temperatures in the table is allowed) when the motor is operating at maximum continuous current rating of the top drive drill motor. The top drive is a drilling machine that is constantly manned by an operator when in use. The top drive control system that the operator interfaces with monitors the temperature of the top drive drilling motor and the operational status of its external cooling system. The top drive control system also limits the amount of continuous and intermittent current that can be applied to the top drive drilling motor based on its continuous full load amp current rating during drilling, makeup, and breakout operations.