A Cable Vault Heating Assessment Study

The Con Edison of New York electric distribution networks have operated reliable for years in underground conduits and vaults. Multiple cable failures in these structures, however, can seriously degrade the reliability of the system. This is especially true during summer heat 0waves where the ambient temperatures and electric loads are at their highest. Con-Edison has recently opened its Cable and Splice Center for Excellence to predict and prevent these cable failures. The center has constructed a full size cable-vault and conduit system where actual field conditions can be simulated. Test cases are being run to examine various ambient and line current conditions that can contribute to a cable failure. Experimental results from one early version of a simulated vault have been benchmarked against an ANSYS finite element thermal-electric model. This benchmarking demonstrated the reliability of the ANSYS modeling techniques. As a result, the analytical method can now be used to examine a variety of simulated cable vault configurations as well as an endless variation of cable vaults in the field. This paper will illustrate the analytical methods used and demonstrate correlation with the simulation model.

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