Earth Ambient Temperature. This is the temperature of the soil surrounding the cable. This temperature varies either cyclically through the year, with the maximum earth ambient temperature generally lagging one or two months behind the corresponding air temperature or remains constant depending upon the depth of the burial. However, high ambient earth temperatures and heavy system loading tend to coincide in the late summer. Earth ambient temperatures can often be obtained either from local soil conservation services or by the use of thermal probes. Representative Maximum Summer Ambient Earth Temperatures are shown in Reference 3, EPRI Underground Transmission Systems Reference Book (1992 Edition).
