Determining high voltage cable conductor temperatures

The tests for checking high voltage products (joints, terminations, connectors, bushings) are described in standard HD628-S1. Some tests require an elevated temperature. For these tests, one must guarantee that the conductor temperature remains within strict limits (5K to 10K above the maximum conductor temperature). To achieve this in fluctuating ambient conditions, one must regulate the current. This means that one must measure the following values simultaneously: conductor temperature and current. However, this is not possible because the voltage in the cable is too high. This makes it impossible to measure the conductor temperature directly. One must determine the conductor temperature (which must be kept within strict limits) in another way. The answer can be found in Appendix A of this standard. The authors carry out a no-voltage pre-test (calibration) i.e.: a 1st method enables them to obtain the relationship between the conductor temperature, the ambient temperature and the current. With a 2nd method, they obtain the relationship between the conductor temperature, the cable-jacket temperature and the current