Dynamic insulation temperature estimation of external gas pressure cables at discretely distributed points

Abstract:
In larger cities all over the world gas pressure cable systems form transmission grids at a voltage level of 64/110 kV. The beginning of their development reaches back to the early 20th century. According to the estimation of experts and manufacturers, the life span of such cables has been calculated to be approx. 40 to 50 years. In recent times a significant number of cable routes and sections reached or exceeded stated life span. To ensure further safe operation monitoring methods are necessary that allow premature detection of failure initiation. One of the most crucial factors for safe operation is keeping the insulation and conductor temperature below specified threshhold values. For monitoring purposes modern cables routes are usually equipped with optic fibers, an installation lacking for most gas pressure cables. However there are few exceptions where sections of cable routes are accordingly equipped between the cable strands. This paper investigates the correlation between the pressure pipe‘s surface temperature and load dependent insulation temperature as a method for temperature monitoring at discrete measurement points. A lab test setup that uses evenly distributed thermocouples as well as an according digital twin were realized to be able to estimate the median and discretely distributed load dependent insulation temperature of unequipped gas pressure cables.