RATING OF ELECTRIC POWER CABLES IN UNFAVORABLE THERMAL ENVIRONMENT BY GEORGE J. ANDERS

RATING OF ELECTRIC POWER CABLES IN UNFAVORABLE THERMAL ENVIRONMENT BY GEORGE J. ANDERS

Contents:

1 Review of Power Cable Standard Rating Methods

2 Ampacity Reduction Factors for Cables Crossing Thermally Unfavorable Regions

3 Cable Crossings-Derating Considerations

4 Application of Thermal Backfills for Cables Crossing Unfavorable Thermal Environments

5 Special Considerations for Real-Time Rating Analysis and Deeply Buried Cables

6 Installations Involving Multiple Cables in Air

7 Rating of Pipe-Type Cables with Slow Circulation of Dielectric Fluid

Preface:

The focus of this book is the calculation of the current-carrying capabilities' of the cables crossing unfavorable thermal environments.However, in order to make this book self-contained and more accessible to a wide group of interested readers, a comprehensive review of the rating methods for standard installation conditions is also included. Cable rating standards deal with uniform laying conditions only; however, in modern cable installations, such conditions are encounteredvery seldom. Cable routes often cross heat sources, including other cables, or pass through regions of high soil thermal resistivity, for example, in the vicinity of trees or shrubs. Air, walls, ceilings, or floors form an impediment to heat flowing away from the cables. In all such situations, the rating of the cables should be reduced to avoid overheating. There has been little attention devoted in the past to the requirement of ampacity derating in such cases. The fact that there have been relatively few failuresattributed to cable overheating is a result of the conservativedesign procedures used by cable engineers. With the economic pressure arising from the restructuring of the electric power industry around the world, the transmission circuits are becoming more heavily loaded and hence more prone to thermal overloads. Better understanding of the heat transfer phenomena around loaded electric power cables will not only help to establish correct transmission line limits, but also may help the circuit owner in the implementation of corrective measures needed to increase cable ratings. Thus, in addition to improved computational procedures, including probabilistic analysis, optimization of thermal backfill design will become more common. This book is aimed at providing cable design engineers and power network analysts and operators with the computationaltools and techniques to ad dress challenges arising from installation of power cables in a complex thermal environment.