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Practical Power Cable Ampacity Analysis

Velimir Lackovic, MScEE


Course Outline

Cable ampacity studies calculate the current-carrying capacity (ampacity) of power cables in underground or above ground installations. This ampacity is determined by the maximum allowable conductor temperature. In turn, this temperature is dependent on the losses in the cable, both I2R and dielectric, and thermal coupling between heat-producing components and ambient temperature.

The ampacity calculations are extremely complex. This is due to many considerations, some examples of which are heat transfer through the cable insulation and sheath, and, in the case of underground installations, heat transfer to duct or soil as well as from duct bank to soil. Other considerations include the effects of losses caused by proximity and skin effects. In addition, depending on the installation, the cable-shielding system may introduce additional losses. The analysis involves the application of thermal equivalents of Ohm’s and Kirchoff’s laws to a thermal circuit.

This course includes a multiple choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course, the student will:

Intended Audience

This course is intended for electrical engineers.

Benefit to Attendees

Attendee of this course will understand heat flow process in underground cables and how various adjustment factors affect cable current carrying capacities. Also, attendee will learn how to calculate permissible cable short circuit currents and voltage drop. Practical methods will be presented along with detailed solution methodology.

Course Introduction

Cable network usually forms a backbone of the power system. Therefore, complete analysis of the power systems includes detailed analyses of the cable network, especially assessment of the cable ampacities. This assessment is necessary since cable current carrying capacity can depend on the number of factors that are predominantly determined by actual conditions of use. Cable current carrying capability is defined as “the current in amperes a conductor can carry continuously under the conditions of use (conditions of the surrounding medium in which the cables are installed) without exceeding its temperature rating limit.”

Course Content

In this lesson, you are required to download and study the following course content in PDF format:

Practical Power Cable Ampacity Analysis

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.

Course Summary

The aim of this course is to acquaint the reader with basic numerical methods and methodology that is used in cable current sizing and calculations. Also use of computer software systems in the solution of cable ampacity problems with emphasis on underground installations is elaborated.

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

Take a Quiz

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.