Generalized Coefficients of External Thermal Resistance for Ampacity Evaluation of Underground Multiple Cable Systems

Abstract

The Equivalent External Thermal Resistance (ETR) of power cable installations is the principal quantity which determines cable ampacity. Variations of ETR with respect to various cable designs and surrounding parameters are of major interest to cable engineers, especially when the effect of varying many independent parameters (individually or simultaneously), on the cable ampacity, is to be determined.On the basis of accurate analysis of a variety of cable systems, this paper describes a simple technique to evaluate the effects of cable and ambient parameters variations on the computed cable ampacity. The technique utilizes coefficients of ETR of multiple cable systems and their observed linearized characteristics. The paper describes the technique and illustrates its implementation on several cable system examples.

Introducing Mutual Heating Effects in the Ladder-Type Soil Model for the Dynamic Thermal Rating of Underground Cables

“…A similar approach to the one in (7) is presented in [18]. Therefore, the temperature rise at cable p in steady state conditions (3), can be rewritten as:…”

“…The effects of mutual heating from neighboring cables are precisely included in the model with a simple and easy to use formulation based on the image method [3]. An alternative formulation was presented in [18].…”